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 Converting 91 OCC to Posi

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Fred Kiehl
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goldwolfnhn
smparr
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smparr

smparr


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PostSubject: Converting 91 OCC to Posi   Converting 91 OCC to Posi Icon_minitimeSat Dec 03, 2022 6:11 pm

Probably not the first time this has been asked, how difficult is it to convert the stock 2.73 91 OCC open diff to the 3.23 GU5 G80 Posi diff?
Is the Posi better in snow? I know it would help with towing.

Thanks,
Steve
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goldwolfnhn




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PostSubject: Re: Converting 91 OCC to Posi   Converting 91 OCC to Posi Icon_minitimeSat Dec 03, 2022 6:59 pm

posi will get you going better, as if one tire slips the other tire gets power, so it can help in snow, but be very carefull on ice and very slick surfaces, my 94 RMW has posi and out of all my vehicles it's the only one I've ever lost control of, at 20 some MPH on the highway gave a little bit of gas and next thing I'm doing a 180 across four lanes, and thats with an extra 280 pounds in the rear and all season tires. But my problem could also just be the LT1's 330 ftlb of torque at 2000rpm.

though you should be able to keep the 2.73 as thats what mine has with the posi and it's factory
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PostSubject: Re: Converting 91 OCC to Posi   Converting 91 OCC to Posi Icon_minitimeSat Dec 03, 2022 9:30 pm

smparr wrote:
Probably not the first time this has been asked, how difficult is it to convert the stock 2.73 91 OCC open diff to the 3.23 GU5 G80 Posi diff?
Is the Posi better in snow? I know it would help with towing.

Thanks,
Steve

If you can find the 3.23 and a Gov-lok, if that is the posi that the GU5 was in that year, it is not hard to do, but you have to replace the pinion and ring gear setup procedures which may take some tools and skills you might not have. For a drivetrain person or someone who has done them before it isn't bad at all.

A Govlok will not do the super easy end swap on slippery surfaces as bad as other lockers due to how it works, but in the less than 10.5" size they are not known for great durability.

I put a Shurtrack helical gear limited slip in mine with a new set of 3.23 gears and it set up fine and runs silently but I don't drive it in the winter. I would not do a limited slip if I did, but might consider a govlok.
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smparr

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PostSubject: Re: Converting 91 OCC to Posi   Converting 91 OCC to Posi Icon_minitimeSun Dec 04, 2022 1:48 am

So I had a 96 RMW with the tow pack and Posi. I did have at least one icy 180 also. I kinda figured it was the Posi but wasn't sure. Maybe my snow tires are the better investment.
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Fred Kiehl

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PostSubject: Re: Converting 91 OCC to Posi   Converting 91 OCC to Posi Icon_minitimeSun Dec 04, 2022 11:02 am

I have had a few posis over the years, and I have never had a problem in any weather. My first one was a 72 Plymouth Fury. I only got stuck twice with it; once on a sheet of ice, and once when I parked on a heavily crowned road uphill in deep snow.  If you respect the conditions you will have more control of the car, in general,  over the open rear  I had snow tires on it on both occasions.  If you get one tire on dry ground, you can go. I have never had control issues,  but don't recall ever driving on an ice sheet to test control. An electric locker would allow you to have the best of both worlds.

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PostSubject: Re: Converting 91 OCC to Posi   Converting 91 OCC to Posi Icon_minitimeSun Dec 04, 2022 10:33 pm

If snow conditions are your main concern - your later comment is correct. Snow tires will be a MUCH better investment than a Posi, put them on all 4 corners and thoughts of a posi will fade into the background.

Regarding trailer towing - unless you're stuck in the mud or something, a posi won't make any difference in my experience.
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1991BlueBertha




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PostSubject: Re: Converting 91 OCC to Posi   Converting 91 OCC to Posi Icon_minitimeMon Dec 05, 2022 11:27 am

goldwolfnhn wrote:
posi will get you going better, as if one tire slips the other tire gets power, so it can help in snow, but be very carefull on ice and very slick surfaces, my 94 RMW has posi and out of all my vehicles it's the only one I've ever lost control of, at 20 some MPH on the highway gave a little bit of gas and next thing I'm doing a 180 across four lanes, and thats with an extra 280 pounds in the rear and all season tires. But my problem could also just be the LT1's 330 ftlb of torque at 2000rpm.

though you should be able to keep the 2.73 as thats what mine has with the posi and it's factory

I'm willing to bet a posi in the 305 cars wont be an issue at all in winter weather. These things are so under powered, hell, i don't even think mines spun a tire on wet roads... I'm sure it could, but its gonna take some effort.... little bit of gas in an LT1 is alot more than a little bit of gas in our 305s with 170hp or whatever they were lol.
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94Woody

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PostSubject: Re: Converting 91 OCC to Posi   Converting 91 OCC to Posi Icon_minitimeMon Dec 05, 2022 12:49 pm

Hate to break it to you but you are sliding on ICE regardless. I mean, it’s ICE. Some studded tires will help but that’s about it. I have found over the years that slowing the heck down is the best approach for snow. I love watching people fly through it and ending up in a ditch and having to buy a few mailboxes.

Well, loved it anyways, I’m in Floriduh now so that stuff is no longer a concern.

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goldwolfnhn




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PostSubject: Re: Converting 91 OCC to Posi   Converting 91 OCC to Posi Icon_minitimeMon Dec 05, 2022 1:24 pm

1991BlueBertha I know how underpowered the non LT1's can be, I also have a 87 Pontiac Safari with a 307, I havn't even managed to get it to break loose on wet grass.

When I was living in Depere we lived 6 miles from town and the roads where all 55mph by us, so it was hilarious the first time I'd go into town especially the first snowfall of the year or any majpr snowfall, how many vehicles had ended up in the ditch or where still in the ditch, and I would really laugh when it was a jacked up 4x4 in the ditch.
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Serendipity96

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PostSubject: Re: Converting 91 OCC to Posi   Converting 91 OCC to Posi Icon_minitimeSat Dec 10, 2022 6:59 pm

when i had my 96 i was going to get an eaton posi - both of my wagons are/were tow packs and BOTH came without factory posi... had several people suggest not to bother looking for a donor from another wagon/sedan but to get a new one as the old one is... well old and likely worn out what with the work to swap it, hardly worth the savings.
Not much snow/ice experience, but lots of wet florida roads and I would on occassion try to get the old 96 wagon to 'drift' on a power turn but was always able to keep it controlled single sided fishtail out - just too much weight and not enough power to 180 on a wet road with decent tires.
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smparr

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PostSubject: Re: Converting 91 OCC to Posi   Converting 91 OCC to Posi Icon_minitimeTue Dec 13, 2022 11:40 pm

Decided to just update to snow tires. Here she is with her snow shoes and base hubcaps. Can't say I like the look of black walls. Looked kinda cop carish with plain steelies before I added the hubcaps.
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PostSubject: Re: Converting 91 OCC to Posi   Converting 91 OCC to Posi Icon_minitimeWed Dec 14, 2022 8:02 am

What make/model of snow tire did you put on?
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smparr

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PostSubject: Re: Converting 91 OCC to Posi   Converting 91 OCC to Posi Icon_minitimeFri Dec 16, 2022 8:23 pm

The only one I could find in 225/75-15 was Firestone Winterforce 2UV.
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vivix




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PostSubject: Re: Converting 91 OCC to Posi   Converting 91 OCC to Posi Icon_minitimeTue Dec 20, 2022 2:02 pm

good luck with the winterforce 2's. Had them on my fiesta and they were ok in the snow and scary in the wet if pushed. that was with a lsd, fwd, torquey thing on 185's though so YRMV
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PostSubject: Re: Converting 91 OCC to Posi   Converting 91 OCC to Posi Icon_minitimeTue Dec 20, 2022 2:26 pm

Take a look at this link to Tire Rack.  It only shows the one you list under winter tires, but with "severe snow service" selected you get more.  A couple aggressive, some touring.  Eliminate the trailer rated onels.

https://www.tirerack.com/tires/TireSearchResults.jsp?width=225/&ratio=75&diameter=15
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smparr

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PostSubject: Re: Converting 91 OCC to Posi   Converting 91 OCC to Posi Icon_minitimeTue Dec 20, 2022 4:40 pm

We just got shellacked with snow and the tires did good driving in 6" on our streets. They did not do well on the ice sheet uphill down the road yesterday! Unfortunately some tard in a crowd killer Mustang gave up in front of me with no way around him. So if course I got to sit with him until a deicer truck came by. They probably would have done better if I'd had the studs put in.
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