700R4 TCC shudder

David is it still driveable right now? Because I may have got my dad convinced to buy this from you.

95BRMW wrote:

Ok, got some useful info from gauge (finally). Here are my pressures at idle with everything warm:
Park- 65 PSI
Reverse - 105 PSI
Neutral- 65 PSI
Drive- 65 PSI
3 (regular D)- 65 PSI
2- 140-145 (fluctuates)
1- 125-130 (fluctuates)
All of this is at idle. I noted if I took the TV cable off the TBI the pressure would increase to about 80 PSI in park.

Cruising on the highway, around 1500 RPMS, 60-70 MPH, the pressure is at 70 PSI. When the TCC locks up and the car starts to shudder, it holds steady and maybe moves 1-2 PSI, the needle is pretty much steady. So, is it worth dropping the valve body and checking the screens? Or is my torque converter tired? Maybe a third thing?

Ok re-reading this,. your "shudder" may not be trans at all,. it maybe the ignition is weak, and causing a miss when low rpm lean condition is encountered,.so how are the plugs,wire cap rotor etc,.
you,ve changed the 02,. so it,s trimming it as lean as it can,.which will show up a bad plug,.

Nick

I'll have to pull the plugs out and take a look. I do kind of remember seeing some sort of build up on the front 2 plugs when I changed them when I did the tune up. The plugs, wires cap, rotor and dist. are new. I also swapped in a fairly new coil I got with a box of parts. I can't really tell if the engine is running at full capacity, I never drove a good running l03 wagon before. Going from LT1 cars to this one makes it feel underpowered to begin with.


The car is drivable right now. The shifting issue still exists under heavy load, you have to let off the gas to get it to shift, but it does do it.

This sounds EXACTLY like what I'm dealing with! After five months of chasing down running issues, and finally solving them, I am still left with what I'll describe as a BONK-BONK kind of bucking at light throttle especially on an incline. I believe it is aTCC issue but I don't know enough about it to prove it.
I thought the rough running and bucking were related but they were coincidental as far as I can tell. I will try adjusting the TV to raise the pressure and see what happens. After that I'll probably just live with. After all, it has 228K miles on it!

Thanks for sharing your info!!

I think Nick is definitly on to something here. I took the cruiser into work today for the first time in a week and a half. It idles a bit rough now, and just seems to have no power. I checked out the plugs last night and I found the front plug on each side has some oily black crap on them, and the rest are clean and almost new looking.

Small progress has been made, if you can call it that. Being there's no power here right now, its the perfect time to take a look at the engine in the dark. I noticed a constant blue flash that appears to be between the plastic coil housing and the mounting bracket. It may also be arching slightly between the boot of the wire on the coil to the white wire on the coil, but not sure on that. Spraying with water made it more visible. I'm going to put the original coil back in and see what happens. Before I left work today I unplugged the EGR and capped off the vac line, seemed better as well.

I swapped out the coil to the old one that came with the car. In complete darkness I see a blue arc between the body and the frame of the of the coil. Spraying water on it makes it a bit more visible as well. I also noticed this coil is particularly loud, like a muffled constant arc inside the coil. I guess I have 2 bad coils on my hands, what are the odds?

I realize that this thread is months old, but I'd like to share some ideas and keep the topic going because I have and issue with my tc lockup.....
When you get a shudder as a result of a convertor staying in-appropriately locked, what you are actually experiencing is "lugging" much as you would in a stick-shift car that hasn't been appropriately downshifted upon slowing to a lower speed than the gear is intended for. These wagons are over two tons, and most are equipped with 323 gears and 305 engines, so they ARE gonna lug when locked in too high a gear!
Any tune-up deficiencies will be accentuated when this kind of a load is put to it!
If you believe that such a problem is limited strictly to the tc's failure to appropriately unlock, you can easily add a toggle switch to de-power the TC at any time!
The torque convertor power path travels thru the second brake actuated plunger switch that is mounted above the brake light plunger switch. There are two plugs with two wires each (one pair for cruise control cancel and one pair for TC cancel) The pair that are pink and purple are the TC wires I do know for certain that the brake plunger switch is normally closed (connected) and opens (disconnects) when the brake is pushed. The pink wire is powered with full battery voltage when ignition is energized. I'm not certain if there are any downstream controls between this switch and the trans, although I suspect that the purple wire may go to the MAP sensor and a different color wire then continues to the trans (I have to do some more investigation!) If you pull the plug from this (brake pedal) switch the TC lockup will be disabled, so this is an easy test to see if your "shuddering" stops!

My TC chooses to only lock up during extremely light throttle (or not at all) but I can sometimes lug it down to 40 MPH engaged and dis-engage it by tapping the brake pedal. If I finf a purple wire with full voltage at the trans plug, I'll know that my "failure to lock" problem is inside the trans case!

I've done some further research:
The positive power path to the trans is only interrupted by the brake cancel switch before entering the trans (purple wire) On our wagons, there are two other wires in the same plug which are negative trigger wires operated by the computer to lock the tcc. The white wire directly locks the convertor in any gear and has no other controls on it. The light blue wire, when grounded allows the circuit to be completed when the internal 4th gear pressure switch is pressurized (when it's in 4th gear.)
I have no idea why the direct-lock wire even exists, but I have a hunch it's only for diagnostic purposes.
My blue wire is apparently dead inside the trans case, so i either need a pressure switch or there isnt enough pressure to activate. I think I'll get a good shift kit and deep pan before going inside for a look...

I had to put a new trans in my wagon last week...... The transmission shop wired the TCC without the two ground wires.......The 4th gear pressure switch is a one wire (grounding) switch. This means that any external conrol preventing fourth-gear lockup needs to interrupt the power on the purple wire.
What I noticed almost immediately was that under light throttle, the car is able to proceed into fourth gear before 50 mph (and also locks the convertor), but if you try to accelerate at all, the car "lugs" and will not accelerate.
I installed a toggle switch on the purple wire and the problem is solved now!