1996 Buick Roadmaster LT1 355 Project - Need Some Help/Advice!

Hi all,

My '96 RMW has been up on rollers since December while the LT1 was being reincarnated as a 355. (bored .030, new cam/pistons/180cc Dart aluminum heads etc) I'm almost done, and eager to get this beast back on the road, but getting bogged down by the details. I could use a little help from the community (both advice and tracking down the remaining parts) Any help would be appreciated! Here's what I need:

1. Does anyone know where to find the inner fender splash guards? (pic below) Mine fell apart during the process of detailing the engine compartment. The compartment looks beautiful; can't put these ratty splash guards back in there. New ones would be great, but very good condition used guards would work too.

2. This car was missing the plastic part (shroud?) that connects the top of the radiator to the cross beam at the front of the engine compartment. I'm not sure what it looked like to begin with. I included a picture of what I think might be the part. Can anyone verify that? Or shoot me a picture of what its supposed to look like? If anyone has the correct part for sale, I will buy it from you.

3. Radiator--Given the extra power/heat, I need something better than the chintzy radiator currently installed in the car. I think I need something like a 4-core radiator with the trans cooler in it. Any suggestions on manufacturers/models?

4. Headers--This is the biggest question at this point. Someone told me 1 3/4-inch "Tri-Y" style headers are the way to go. If there's a way to do this without buying new cats that would be great. (i.e. bolt up to the existing cats) I'm just not finding much info on header applications for this car/engine combo. Please advise.

5. Torque Converter--I'm staying with the existing 4L60E transmission for now. My aim is to make the car as streetable/driveable as possible given the setup (I'm not taking this car to the strip etc). I need to verify the rear-end gearing (I think its 2.56...is that the standard, non-tow package gearing?) I would welcome any suggestions on an appropriate TC/stall number.

I think that's all for now (still the programming to contend with, but that's for another day) Thanks in advance for your help! Best,

Phil

Your number 1a and B priorities need to be a converter and GEARS. 2500-3000ish stall (but you need to match that to the cam specs), and at least 3.42s (with a new 3 series posi carrier).

Here's the answer to #1: https://www.rubbertherightway.com/1996-buick-restoration-parts-a-58451-prd1.htm

Great quality product and made in the USA.


Tom

Thanks Tom!  I just put the order through.  Beautiful cars you got there.

Jay, I agree with you re: the gearing/TC.  I know I need to do something but my knowledge on that point is limited.  I keep going down internet rabbit holes on gearing etc. and getting no closer to an answer.  3.42 seems more aggressive than I want to go, but I could be wrong. These are the cam specs:

nice cam. Jay is right. Gears/posi/converter 1st. Then headers. 3.42 or 3.73 gears. I like the truetrac posi best but the eaton clutch type works well too.

Tri-Ys I think are 1 5/8'' and are good for what you are trying to do. Clear image automotive sells them, as does stan's headers, both in WA. They pop up used on ISSF regularly. They do not bolt up to stock cats, but they come with either offroad/cat-delete pipes or their own converters.
If you can get you hand on a set of SLP shorties or AS&M shorties, you'd be good to go with stock cats. Performance is decent as well. Probably less than 1/10th difference from tri-ys. Probably a 20hp difference with all the supporting mods.

Thanks Jason. I appreciate the info. I'll poke around the net and see what I can find. As to the gearing, assuming this car has 2.56 (no posi), what's the most direct way to swap out/upgrade the gears? Am I looking at swapping the entire axle assembly out?

You can look at the SPID on the right gate jam. If it has GM8 it is 2.56.

You can put any gear ratio in the housing, but you need to set it up properly. The axle carrier for the 2.56 is different than the others, but the housing is the same. You also need a gearset with pinion shaft that will accept the correct tone ring for the anti-lock brakes.

I just finished building a rear with 3.42 gears, and it was not difficult. The special tools you need are the yoke holder with a couple of 2 foot pipes to fit over the end of it and the breaker bar, an in. lb, and ft. lb. torque wrench, a dial indicator gauge with a magnetic holder, bearing race installer, depth micrometer or calipers, a pinion depth gauge, and a 3-5 lb. hammer. Pieces of pipe and rod stock can be used to install the bearings, and remove the bearing races. The gears come with instructions, and the install kit has all of the shims you need. If you get a Truetrac, you need different set of carrier bearings. I suggest Moser axles, and new bearings if your axles are worn at all. They use a C clip to hold the axle spacer in, and if you lose it, I have extras. You can borrow a lot of the tools from Autozone or O'Reileys.

There are some secrets in putting a rear together that make it easier. If you decide to build one, let me know, and I can share them.

I noticed that you are using roller tip rockers. I recently saw a test of stamped, roller tip, and full roller rockers, and there was no advantage to either the roller tip or full roller rockers under 5500 RPMs, in fact the roller tip rockers fared poorly compared to the stamped units (-4~6 hp). Run 1.6 ratio stamped units unless you are headed over 5500 RPM. Even then, the full rollers may not perform any better, because the ones in the test were a higher ratio than the stamped ones. If I were to do my 454 over, I would use the stamped rockers, and less expensive valve covers.

I have an excellent upper radiator support for sale. $55 shipped

silverfox103 that link is great! I thought those things were long gone. I also see they sell the radiator seals - urbanPhil - having the best radiator in the world is useless if you don't control airflow around it. Make sure the area around the radiator is as sealed as possible and all of your lower airdams below the radiator support are intact.

Nice Project!   The upper plastic radiator support is VERY common.   Was used in both Roadmasters/Fleetwoods and Caprice models without the towing packages.   Find a 94-96 Caprice/Roadmaster/Fleetwood in a wrecking yard and you'll be set most-likely.

Keep us updated on the car!   I really want to upgrade the 2.93 rear in my '96 tow-pack Roady eventually to a 3.23 or 3.42 and am planning to follow-along here!

-Michael

Thanks Fred! You got a deal on the radiator support. Please send me a PM with your payment info. (I don't have PM capability yet) I appreciate the primer on changing the gears and I'll definitely consult you when I'm ready to go in on that. I have code GW9, so I think I have 2.93's (A Buick dealer told me the same, based on the last 8 of the VIN).

It seems like there's varying opinions on the TC/gear combo. My engine builder suggested 2000 stall/3.55. Others have said 2600 stall is more appropriate. I want some punch off the line, but I need this thing to retain some of its street manners. I live in the city, but I also want to take this rig to the lake on weekends (an hour of mostly highway driving each way) So I'd like to keep the mpg in check to the extent possible (I know that ship may have sailed given the nature of the build...)

Mike, thanks for the encouragement! Of course I'll keep posting progress pics and updates. It's the least I can do for all the helpful advice I've received here.

Your cam manufacturer should be your go to guy for TC stall speed. I do not think they make a 3.55 for the 10 bolt. 3.42 is a good gear. 3.23 is a 200 mph gear. All of them are a tradeoff of git and mileage.

I called Comp Cams today. The guy recommended a 2000-2200 stall TC with 3.73 gears. Specifically, the TCI Breakaway torque converter (which seems to be listed at a slightly higher stall number) and Yukon brand gears.

The stall RPM of a rated converter will vary with the amount of HP applied to it. More HP higher stall...within limits of course.

The converter I have is a 24-2600 RPM stall for my 450 HP 454. It probably stalls at about 2600 under full throttle, and maybe 2400 at light throttle. If it were any lower, the car would become "jerky" at low speeds, because of the slightly erratic idle from the cam. With slightly higher gears, you want a higher stall TC because the engine/gear ratio reduces the frequency of power pulses at the wheel.

Be careful about what gears you use. Yukon are supposed to be good, and so are Richmond if you get the higher priced line. One secret to make the gears stronger is to run your pinion a little on the tall side. It places the contact patch closer to the center of the ring gear, and thus will not deflect as much. You can put an EXTRA .030 to .060 shim under the pinion bearing, and just set the mesh. You may be able to put more shims under the pinion bearing, but unless you are really good at it, stick with" "a little is better" theory in this case. The initial shim stack will be about .030 -.060. If you use a .090 shim stack, it will probably be good. I would still measure it.

Thanks Fred. My cousin is helping me with the gears (he's got much more knowledge in this area than I do) I'll pass that information along to him. This is the TC I'm considering:

http://www.tciauto.com/tc/breakawayr-converter-gm-1984-97-700r4-30-spline-1-703-crank-pilot-1993-97-4l60e-1997-05-4l60e-c5-corvette-lock-up-6514html

I still need to call Yukon re: the gears/rebuild kit etc.

Thanks for sending the radiator support out so quickly. Any chance you could post a picture of your "oriental carpet on the bed"? I gotta see this...

Carpet in the bed picture.

Ever take anyone for a magic carpet ride? Just to be clear,I don't want one. Lol!!!

str is what makes a converter more friendly
stall torque ratio. the torque at which it needs to slide to its max rpm
A tight converter will act like a stocker until you push it and it slides
i drove a 95 ss impala with a 3200 edge that acted pretty much stock until you went past 1/4 throttle or so. i had a 2800 vigilanti was tight too. worked great with 3:73's
putting a stall converter up against tall 2.56's will be abysmal,. something a kin to driving a bus.

you'll get a lot of opinions about gear ratio's,. find out which opinions are from practical experience,. and which opinions are just regurgitated internet hyperbole

That's amazing Fred. Thanks for sharing. LOL @ "magic carpet ride."

I got temporarily waylaid by work obligations, but I'm getting back on mission. Hope to have more updates for you soon.

Thanks Phantom. I'm narrowing down my choices. 3.73's with something in the 2000-2600 range is the leader in the clubhouse. Any opinion on the optimal stall number to pair with 3.73 in this car? (erring on the side of driveability)

If the cam manufacturer gives you a number, use it. The 2000-2400 range is wide for a single converter. You probably get a 2000 RPM range for a converter, and it also has variations with power applied.

[long-overdue] UPDATE:

Hi all.  I hope everyone is well on this Thanksgiving Eve.  I thought you might like an update on this project, so here it is, with photos:

1.  The motor is back in the car and we fired it up for the first time last weekend.   We only ran for a few seconds but it sounds downright nasty! It was a huge relief to have it turn over and run like that on basically the first try.

2.  I got the headers, high flow cats, mufflers, wagon kit (the whole shot) from Dan at Clear Image Automotive. (http://www.clearimageautomotive.com/)  Really nice guy that knows his stuff.  The exhaust was somewhat pricey but the fabrication is top-notch. (*note that the clear image website has not been updated in some time so the prices are a little higher than the listed prices)  The driver's side header went in pretty easy.  The other side was tight (I had to remove and reinstall the dipstick tube to get the header in there).  Header gaskets were Felpro FEL-1470.

3.  For the torque converter I went with the B&M Holeshot (listed at 2000 stall) (https://www.summitracing.com/parts/bmm-70417)  There's not many choices in the stall range I was looking for (you get a lot more choices at 2600+ it seems) But I wanted to stay within my engine builder's suggested parameters.  So, we'll see how that works out (not installed yet)

4. I put the trailer hitch on and wired it up. (My cousin thinks is ridiculous but I'll be damned if I'll have  wagon with no hitch)  Annoyingly, the tongue I have is not long enough, so the ball sits right up against the rear bumper.  Gotta do something about that.

5.  Got the ECM reflashed/reprogrammed by TPIS in Minnesota (https://www.tpis.com/pages/efi)

6.  I still need to install the radiator, electric fan(s), transmission, TQ, and exhaust.  I'm sure there's more (always is!) but it's getting there.

More to come, but here's some progress photos.  Happy to answer any questions if I can.  Happy Thanksgiving.

You should either wrap the headers, or wrap everything else to keep the heat from damaging wires, and hoses. Headers run much hotter than the stock manifolds.

Hi everyone! Sorry for the long break. I've had the car back since August and I meant to give you an update long before now. I hope everyone is healthy and making the best of quarantine (at least we can still drive!)

A lot has happened since my last update, so I'll just cut right to the raw numbers: the dyno says the modified LT1 is making 337 hp/397 tq at the crank (260/300 is stock) The low end is where it's at with this car. When you mash the pedal the car gets moving in a hurry and it can rip a mean [one-wheeled] burnout (much to the surprise of any onlookers) Frankly it's awesome that an object that big can get moving that quick. I'll try to load up some videos for you. For all the low end power, the car is relatively quiet highway cruiser just like it was before.

I ended up getting the headers ceramic coated instead of wrapped and it was well worth it. The heat control on this motor is phenomenal. The temp gauge never goes past 1/4 no matter how much I beat on it or how hot the outside temp is. The coating looks good too. (again I will post pics)

I still haven't touched the transmission or the gears (2.93), so I believe the car is capable of more. I don't know how long the 4L60E will hold up to the extra power. It's got 146K on it and has recently developed a slow fluid leak (I was just happy it wasn't oil). There are some times when it's a little slow to respond to throttle; other times it's searching for the right gear. It won't always reliably grab the passing gear when you want to blow by someone at highway speed. So I have some work to do there. (Right now I'm working on some of the cosmetic stuff that's been bugging me...)

I'm sure I've left something out of this update, but I'm happy to answer questions if anyone has them. I'll work on getting some pics/videos/dyno graphs posted on here. In the meantime, everyone stay healthy and safe. TTYS.

Phil

Proper ignition timing does an amazing job with heat control. GM generally runs the timing VERY conservative on engines for a number of reasons, but the earlier you can light off the mixture, the more heat actually gets transformed into usable work instead of going into the water jacket and exhaust. In fact, if you ran fully optimized timing on cold start, there's a fair chance your engine would never fully warm up in the winter.

Personally, unless you want to be a stoplight queen, 2.93 - 3.42 gears is all you need.  I'm putting 3.23s in my own wagon.  I enjoy a nice highway ride and I'm building a torque motor just like yours. Definitely spend the money on a good smaller-diameter torque converter.

As to the transmission shifting, pay attention to HOW you move the gas pedal. The PCM looks for the rate of change and will downshift accordingly. If you just lean into the gas pedal, it's much more likely to hold the current gear.  Try quickly letting off and then back onto the gas, and that'll tell the PCM you want a downshift NOW. You can control the transmission with the gas pedal in these cars if you know how to do it.  BTW, if you're still running the stock '96 computer, there aren't a lot of good nor cheap tuning options at the moment; I'm working with some guys on changing that, but it may be a bit. But you can tune the heck out of the transmission behavior, and my old '94 shifted perfectly every time after a bit of tuning. '94-95 owners can adjust their shift points to perfection right now with TunerPro and EEhack.

Regarding your transmission, I recently wrote a guide on what updates I'd recommend. But if yours is original, the seals and bushings are probably shot, and the valvebody is worn, so a rebuild would be a good idea. You can read more here:  "While it's out, anything I can do?"

Fred Kiehl wrote:

The stall RPM of a rated converter will vary with the amount of HP applied to it. More HP higher stall...within limits of course.

The converter I have is a 24-2600 RPM stall for my 450 HP 454. It probably stalls at about 2600 under full throttle, and maybe 2400 at light throttle. If it were any lower, the car would become "jerky" at low speeds, because of the slightly erratic idle from the cam. With slightly higher gears, you want a higher stall TC because the engine/gear ratio reduces the frequency of power pulses at the wheel.

Be careful about what gears you use. Yukon are supposed to be good, and so are Richmond if you get the higher priced line. One secret to make the gears stronger is to run your pinion a little on the tall side. It places the contact patch closer to the center of the ring gear, and thus will not deflect as much. You can put an EXTRA .030 to .060 shim under the pinion bearing, and just set the mesh. You may be able to put more shims under the pinion bearing, but unless you are really good at it, stick with" "a little is better" theory in this case. The initial shim stack will be about .030 -.060. If you use a .090 shim stack, it will probably be good. I would still measure it.

I found that the thickest pinion shim that should be used is about 0.042. Mine has a 0.038 shim, and the mesh is perfect. I have been taken down a couple of dead end roads with the rear rebuild. I now have it in the car, and I can tell the difference even with the miniscule change from 3.23 to 3.42. It used to have a little tire spin when leaving the line by mashing the gas pedal, and now it leaves a lot of rubber on the street with the same launch. I am surprised at the difference.

Sherlock--I agree with your take on the gearing.  Let me know how the 3.23's work for you.  I like the low end burst but I also take the car to the lake on weekends so I still need it to be a smooth cruiser at highway speed.  

I had the PCM reprogrammed by TPIS in Minnesota based on my specs, and then tweaked by a local dyno shop after I installed the motor.

On the transmission question, any thoughts on whether it's better to rebuild vs. replace with a new 4L60E?  I haven't done any cost comparisons on this yet.  Looks like a new 4L60E can be had for $2000-$2500 on Summit though.  I'd like to get your thoughts on this because there might be factors I'm overlooking.  

Fred, that gear change sounds enticing.  When this car's having a good day I'm hesitant to change anything.  But I know the car could be doing better (and I need to address this leak anyway)  so I'll get around to it at some point...

In the meantime I'm trying (and failing) to fix my power antenna. I'm shocked at how difficult this is...

Power antenna are a PITA to fix. The main problem is the cable breaks. They are miserable to open, and extremely dirty both inside, and out. I have recently explored replacing the cable with a 1/8 inch steel one. It has been working well, and I may repair some more. I did a write-up on it somewhere on the forum. I think it was in the "antenna party" thread. 

You should be able to get a transmission built locally for substantially less than $2000 including a torque converter. There are some threads on transmissions here and on ISSF. You will not have to pay shipping, and you would have to pay for installation either way.

Depends on what kind of warranty service you want.  Anybody can rebuild the 4L60E, and many can get it to last. It's what happens when it breaks.

I use Jasper for all transmissions I don't build myself. Out of four I've had personal dealings with in my immediate family, only one had an issue, and of course it was 700 miles from home when it failed, with my wife driving and I at home. Jasper has a 3-year 100k warranty and we opted for the upgraded warranty, and a local Jasper-affiliated shop took care of the whole issue with only one day delay in the trip. There are other nationwide companies like ATK and GM that offer similar warranties.

Personally I would shop based on warranty.  Be sure to tell them your vehicle and powertrain, in writing, ahead of time, so they can't come back to you later and try to blame it on you. If you get a local shop to do it, get it in writing that they will pay the tow fees back to their shop, or they will pay to have it diagnosed or fixed wherever it breaks.  Something like that.

UrbanPhil wrote:

Sherlock--I agree with your take on the gearing.  Let me know how the 3.23's work for you.  I like the low end burst but I also take the car to the lake on weekends so I still need it to be a smooth cruiser at highway speed.  

I had the PCM reprogrammed by TPIS in Minnesota based on my specs, and then tweaked by a local dyno shop after I installed the motor.

On the transmission question, any thoughts on whether it's better to rebuild vs. replace with a new 4L60E?  I haven't done any cost comparisons on this yet.  Looks like a new 4L60E can be had for $2000-$2500 on Summit though.  I'd like to get your thoughts on this because there might be factors I'm overlooking.  

Fred, that gear change sounds enticing.  When this car's having a good day I'm hesitant to change anything.  But I know the car could be doing better (and I need to address this leak anyway)  so I'll get around to it at some point...

In the meantime I'm trying (and failing) to fix my power antenna.  I'm shocked at how difficult this is...

The 3.42s are indistinguishable from the 3.23s as far as driveability. The 3.23 gears are effectively about 200 mph gears. Of course the 3.42s are not much of a difference. 0.19 ratio drop. That would make them about 190 mph gears. Since the cars are not going to go that fast, unless the HP is bumped up a lot, it is a matter of launching, and if you have fun laying some rubber.

Try using a dremel with a 1/8 inch carbide end mill to get the rivets out. Once they are out, it becomes much easier. I pry the mast out of the motor case, then start working on the motor case.

So I misread your question - a rebuild vs. a replacement at this point is a non-question because there are no new 4L60Es being bulit by GM, so they're ALL rebuilds.

Hi Sherlock--Thanks for the info. Yes, I'm basically asking whether there's any difference in build quality, performance etc. with a "new" transmission from Summit (for example) vs. having a local shop rebuild mine with the new specs in mind. I'm waiting for a call back from Continental to get a price estimate on the rebuild.

Fred--so by going from 3.23 to 3.42, I could possibly make some gains off the line and give up nothing as far as highway driveability? That sounds like a pretty good deal. TY.

On the topic of 3.23 vs 3.42, maybe consider a couple hundred RPM higher stall torque converter instead of switching gears. This will get the engine higher into the powerband, a bit more torque multiplication for takeoff/tire burning, but not effect highway cruising RPM's since the torque converter is locked up in those conditions.

You're going to buy a torque converter with a new transmission (you should anyway) so no additional cost or work to go this route.

Similar results, different approach - just something to consider...

I replaced the stock torque converter with the B&M Holeshot (listed at 2000 stall):

(https://www.summitracing.com/parts/bmm-70417).

Unless you have an aluminum driveshaft, driveshaft rpm is always a concern in these cars due to the length of the driveshaft. Gear ratio availability is also a factor - I am going 3.23 because I have a gearset and ABS reluctor here for it. A buddy wanted 3.23s and we were unsuccessful in finding a new set. Make sure you're able to get the correct ABS reluctor as well, otherwise your ABS won't work.

I removed the ABS on mine, so I did not worry about the tone ring for the ABS. You do need the correct one to maintain your ABS.

Welp...the old 4L60E finally gave up the ghost.  The car moves but will not grab 3rd gear when you apply real power to it (when it does grab it's weak as hell)  I don't remember any precipitating event but something is definitely wrong...

The trans does not give much of a warning. They just stop working. If you are going to get it rebuilt  locally, look for a shop that builds racing transmissions. They should know all the tricks to make it bulletproof.

Just a note on final gear ratios. You can often go faster with a slightly higher numerical ratio, because  the engine gets power multiplication from the ratio. There is a limit to the increase when you run out of rpms. If you are going about 150 max, you can try running it in 3rd, instead of 4th, and see if it goes any faster.

At this point, I'm leaning toward getting a crate 4L60E from Summit or Jegs--one of the units rated up to 450 hp, which should be plenty for this car for the foreseeable future. (I google "LT1 supercharger" about once a week but it's mostly a pipe dream) I need something relatively plug-and-play to get me going again (and quick! I don't want to lose too much of the summer screwing around with this). Do you have any experience with the crate units? Is one better than the others?

The gears will probably have to wait a bit. Does it make more sense to look for a whole rear axle assembly with the desired gearing already in it?

As always, thanks for sharing your wisdom and enjoy this snowy Mother's Day.

UrbanPhil wrote:

At this point, I'm leaning toward getting a crate 4L60E from Summit or Jegs--one of the units rated up to 450 hp, which should be plenty for this car for the foreseeable future.  (I google "LT1 supercharger" about once a week but it's mostly a pipe dream)  I need something relatively plug-and-play to get me going again (and quick! I don't want to lose too much of the summer screwing around with this).  Do you have any experience with the crate units?  Is one better than the others?

The gears will probably have to wait a bit.  Does it make more sense to look for a whole rear axle assembly with the desired gearing already in it?

As always, thanks for sharing your wisdom and enjoy this snowy Mother's Day.

What does Summit do if the trans needs a warranty repair? Make you pull it and mail it back to them? I would buy local so it can be warrantied local if needed. It should be fine though because the things are old enough and their problems/remedies are well known by all builders.

As for the rear end that depends upon what one finds. I have seen folks ask more for a rear than the parts needed to build your own. Of course if one doesn't want to/cannot build their own it saves them the hassle. Of course you also pay for parts of unknown quality. $500 for a rear just to have the posi unit fail in a week means you are spending that $500 again.

94Woody wrote:

UrbanPhil wrote:

At this point, I'm leaning toward getting a crate 4L60E from Summit or Jegs--one of the units rated up to 450 hp, which should be plenty for this car for the foreseeable future.  (I google "LT1 supercharger" about once a week but it's mostly a pipe dream)  I need something relatively plug-and-play to get me going again (and quick! I don't want to lose too much of the summer screwing around with this).  Do you have any experience with the crate units?  Is one better than the others?

The gears will probably have to wait a bit.  Does it make more sense to look for a whole rear axle assembly with the desired gearing already in it?

As always, thanks for sharing your wisdom and enjoy this snowy Mother's Day.

What does Summit do if the trans needs a warranty repair? Make you pull it and mail it back to them? I would buy local so it can be warrantied local if needed. It should be fine though because the things are old enough and their problems/remedies are well known by all builders.

As for the rear end that depends upon what one finds. I have seen folks ask more for a rear than the parts needed to build your own. Of course if one doesn't want to/cannot build their own it saves them the hassle. Of course you also pay for parts of unknown quality. $500 for a rear just to have the posi unit fail in a week means you are spending that $500 again.

With the price of a major component, and distance involved, 94 Woody has my vote. Keep it near home. My policy in life is anything with a warranty should be sourced within 5 miles or 5 minutes, whichever comes first.

All great points. I was planning to spend some time on the phone with Summit re: the warranty. I'll check out the local builders too. I tried the place within 5 miles and they failed to return my call twice so I need to cast a wider net. I'm thinking my dyno guy might point me in the right direction locally. He knows his stuff and I'll need to see him for a re-tune anyway. Thanks for all the help. I'll keep you posted.

UrbanPhil wrote:

All great points.  I was planning to spend some time on the phone with Summit re: the warranty.  I'll check out the local builders too.  I tried the place within 5 miles and they failed to return my call twice so I need to cast a wider net.  I'm thinking my dyno guy might point me in the right direction locally.  He knows his stuff and I'll need to see him for a re-tune anyway.  Thanks for all the help.  I'll keep you posted.  

You may want to check with a few local pickup truck performance shops. They may have references to trans shops that do a good job on the 4L60's in heavy vehicles as that is what they deal with all the time.

Yes - the shops that do delivery vans, plow trucks, etc. will know how to build them to last. Especially if you ask them if they use Sonnax parts and they smile and say "yes." Most guys I know with 3-4 clutchpack failures on rebuilds tend to experience it around 30,000 miles after the rebuild, which nobody ever puts on their cars in the "one year unlimited miles" warranty most shops put.

At your power level and with a non-stock converter I'd really want to see the shop use the following Sonnax parts:
74140-01K Heavy Duty 3-4 clutch backing plate kit
77733-02K Input Drum Reinforcement kit
77754-03k TCC Regulator and Isolator Valve Kit

You might just have to call them to see what's actually in the build list.

If you go supercharger, you might look at the Smart Tech input housing and the larger 2nd and 4th servos, but those can be added later when you put the supercharger on.  They're $$$ too.

I hear what Fred is saying but I had a mom and pop rebuild that failed 500 miles from home, and I was SOL. If you drive any distance, figure out ahead of time what shops are along the way or at your destination. Jasper has affiliated shops in every town/city where my relatives and friends live (in fact they'll even reimburse non-Jasper shops), and GM dealers can most likely service GM rebuilds. Trust me, IF you have a problem, this will pay for itself the first time you have an issue.

There's a lot of twaddle out there regarding gear ratio's.
Personally with such A heavy car i always run 3.73's, i've had numerous B bodys,. The ease of passing and rolling up hills without having to unlock the converter is perfect,.  2:56's are hard work,.
I've driven with every gear ratio from 2:56 down to 5:13's
The 3:73's are best all round.  Top speed is improved, a wagon tuned right stock with 3:73's will run 140+ mph.  I have been across the countries from east coast to west coast 3:73 inmo is the best all round. Motor stays cooler because its not working hard.
Dwywyga.

Hi all.  It's been a long 10 days with this car...

First (and most importantly) the transmission is rebuilt and back in the car.  I took your advice and stayed local.  Unbeknownst to me, a friend of mine previously worked for the premier transmission shop in the area for 20+ years.  On his referral, they did a race-rebuilt 4L60E with a Corvette servo and all the other good stuff, with a one-year warranty.  Got it done in 3 days.  Great service and I couldn't be happier with the results.  

It's like night and day.  The car used to labor in 1-2 for way too long (loudly) and then snap into 3rd real hard when you stepped on it.  Now it's a smooth, fast, and efficient transition from 1-3; the passing gear is improved at highway speed etc.  It's just more driveable all the way around.

Phantom--funny you say that; the transmission tech was all about the 3.73 for this car too.  I'll be bringing it back to them for that...not any time soon unfortunately because the car is beating the hell out of me this week!  Besides the trans, I've had to:

Replace the 2 [unsafe at any speed] rear tires (already scheduled prior to the tranny implosion);  
Replace the battery (my formerly new-ish battery died of neglect while motor was out);
Replace the alternator (AC Delco unit outlived its warranty by one month, volt light started coming on a couple days after transmission job)
Replace front wheel bearing(s?) (*scheduled for next week* No choice, the squealing is out of control; really detracting from the beautiful sound of the motor)
Replace Blower Motor Resistor (crapped out a month ago; not a big deal when it was cold but now I need that AC!) Anyone know where to get this part for < $160? That's what it seems to be listed at.  I'll go to the u-pull-it if I have to...

So that's where I'm at! Enjoying the hell out of my project vehicle already this summer.  I hope everyone is well.  Thanks again for your help on this.

Get the blower motor control from the JY. They are cheap there. Get a spare while you are there.

Hi all.  I hope everyone had a great summer.  I'm looking to swap out my differential gears for a posi unit before the snow flies.  Phantom 309--I was initially swayed by your robust endorsement of 3.73's and I'm still leaning that way, but I was hoping you could confirm that my math is right.  

Currently, with the 2.93's, my motor is turning 1900 RPM @ 75 mph (according to the secret tach in the climate control).  That's consistent with the numbers produced by this transmission gear ratio calculator:

https://www.engineersedge.com/mechanics_machines/transmission-gear-ratio-calculator.htm

*I ran the numbers using 235/70/15 tires (Diameter = 709.985) and 2.93 Final Gear Ratio, along with the 4L60E gear ratios: 1st: 3.06, 2nd: 1.63, 3rd: 1.00, 4th .70 (I tried to upload photos of the graph but the longroof forum would just not allow it...)

If you change the final gear ratio to 3.73, the graph says the vehicle will be doing 63.67 mph @ 2000 RPM in 4th gear.  That number gave me pause because generally on the highway I'm cruising at 70-75 mph.  I'm not concerned so much about the gas mileage (that ship has sailed) but I need the car to make a weekly 60 mile trip to the lake in relative comfort.  However, only 20 miles of that is at highway speed so maybe it's not a big deal.  

Is this an accurate way to figure out where the RPM's will be at 75 mph with 3.73's?:

2000 RPM/63.67 mph = 31.411968 (RPM per mph) *these are the numbers from the 3.73 graph*
31.411968 x 75 mph = 2356 RPM

If this is accurate, the RPM's are lower than I'd thought they'd be.  Is 2356 a reasonable place to be at 75?  I feel like it might be worth it for the low end gains.  The vast majority of my driving is city driving.  It would be great if the motor didn't have to work so hard to get the car into it's power band.  

Anyway, thanks for looking.  Any advice would be appreciated. I hope everyone is healthy.  Best,

Phil

A quiet exhaust will make higher rpms quite tolerable. If you don't already have resonators on your system, add some. Vibrant Performance and Dynomax both max resonators you can add in that will cut 4dB out of your exhaust and kill drone without sacrificing performance.