Horrible brakes vibration!

[Tuddi]

Hi there turbokinetic.

You talk about the tranny locking up in 3rd gear.

I have the same darn problem from time to time.

No matter how I adjust the TV cable, it will lock itself in 3rd, and if I slow down to a stop, the engine stalls because it doesn't shift down to 1st gear. Then I have the problem of getting the darn car out of the spot again (blocking traffic is no fun). When it has locked itself in 3rd, I can't even use manual 2nd or 1st gear to get it going.

My ride is 1985 Chevy Celebrity, V6 2.8 carbed model (X) with no overdrive or special features.

I have never had the need (before) to fix a tranny, but you seem to be knowledgeable about such operations. What's your advice?

[turbokinetic]

You talk about the tranny locking up.... engine stalls...... blocking traffic.... can't even use manual 2nd or 1st gear to get it going....

This is the famous TCC valve sticking problem with the THM125C. Really, it is probably shifting down, but the converter clutch is staying locked-up and killing the engine.
The 125C has a design where the converter "apply" oil comes from the main line pressure circuit, through the control valve, and into the clutch "apply" circuit. This works fine when all the valves are working and the ECM and brakes switch turn off the clutch when you slow down. But if the valve sticks, the converter clutch will stay locked up and stall the engine, like trying to stop with a manual box and not use the clutch!
There are various fixes for this which all involve removing the transmission end cover and accesing the valve body. I definately remember dismantling the valve body and honing some valves and bores to fix this on one stubborn tranny. There are aftermarket TCC solenoids that supposedly eliminate this issue. Do you have the ATSG manual on this transmission?
For what it's worth, the mighty 440T4 uses oil from a circuit only active in 2 through 4th gear, so even if the TCC valves stick or the electrics malfunction, the TCC releases in first and the engine continues to run.
I'll research it a little more...

[turbokinetic]

Well I just typed a reply and lost it. See if I can remember this a second time.
I can look in my ATSG manual when I get home. If I can find - has been a long time since worked on a 125C.
I remember there were 2 procedures depending on what year. One needed only a new TCC solenoid with bigger exhaust hole, other had to do something to the valve under the TCC solenoid.
The TCC solenoid is under the trans end cover, you have to remove this but no major mechanical disassembly of the transmission is required. IIRC the valve under the TCC solenoid also comes out without major work.
What is bad is when the trans has been run hot or with dirty oil and all the valve bores are scratched and the whole VB has to come off and be worked on.
This is a dangerous problem due to the stalling - hope you can get it fixed soon!

[Tuddi]

Do you have the ATSG manual on this transmission?

Nope. Living down in Peru South America is a perfect way to be far away from spareparts, manuals and such remedies

This problem of mine seems to come into play when the car has been driving for a while and the trannyfluid is hot. For the past week I have had the car in 2nd for the most time, but daring to put it in D when I hit light traffic or have long stretches of road to move on without any stops. Then I put it in 2nd at the start of a slow-down.

Clearly it is irritating as crap... and I'd love to see the last of this sooner than possible.

Thanks for the input, and should you find more info, I'd welcome it (preferably in a thread of it's own).

[turbokinetic]

Will start a new thread when I get the info. Interesting, a friend of mine from Northport, AL started a business in Peru last year.
Have you done much transmission work? The 125C is a simple transmission. If you have done any auto trans work, it should not be hard to fix.

[Tuddi]

Thanks!

No, I have never worked on automatic transmissions... only manual gearboxes and transfer cases.

If I have the basic info for the repair, I am sure I can carry out the whole thing with a (transparent) blindfold... especially if no special tools are needed.

Hope you don't mind me asking what your friend's business is?

[LordDurock]

Nope. Living down in Peru South America is a perfect way to be far away from spareparts, manuals and such remedies

This problem of mine seems to come into play when the car has been driving for a while and the trannyfluid is hot. For the past week I have had the car in 2nd for the most time, but daring to put it in D when I hit light traffic or have long stretches of road to move on without any stops. Then I put it in 2nd at the start of a slow-down.

Clearly it is irritating as crap... and I'd love to see the last of this sooner than possible.

Thanks for the input, and should you find more info, I'd welcome it (preferably in a thread of it's own).

hey tubbi i said this befor but find a forum member you trust and i sure he or she would be happy to ship you new parts

[LordDurock]

Thanks!

No, I have never worked on automatic transmissions... only manual gearboxes and transfer cases.

If I have the basic info for the repair, I am sure I can carry out the whole thing with a (transparent) blindfold... especially if no special tools are needed.

Hope you don't mind me asking what your friend's business is?

i have not this job but it acuttly looks rather easy looking all have to do it take the side pan off (no need to drain the tranny that i know off) and take out the soiliond it rather easy. the only thing that pan for it to protexted the vaule body

[Tuddi]

hey tubbi i said this befor but find a forum member you trust and i sure he or she would be happy to ship you new parts

Yes, I saw your comment earlier thank you. I have done business through Don, and will not hesitate contacting him again for more parts if/when the time is up for it, and if he can assist again.

One more question to those in the "know" ... is it possible to fix the solenoid if it is faulty? Or is it sealed in plastic and beyond repair? Anyone have a picture of what it looks like?

[turbokinetic]

http://68.209.87.173/Temp/125C_TCC_sol.jpg

I think there is an oriface in it that is different in the new ones.

[85_Ciera_Rebuild]

The 125C is a simple transmission.

I've done manual boxes before....but without specialized shop tools, could it be taken apart and re-assembled without specialized tools? Could you make do with existing mechanics tools?

I would be following OEM shop book, if I do this task...

[85_Ciera_Rebuild]

...more parts..

This is a trade place for trany parts....never tried them, but was thinking about it next year:


For export information, Non-USA credit cards, APO shipping, see our EXPORT information page .

[Tuddi]

This is a trade place for trany parts....never tried them, but was thinking about it next year:


For export information, Non-USA credit cards, APO shipping, see our EXPORT information page .

Thanks for the links!

[Pontiac6ksteawd]

Hey Tuddi. Yes you can replace the TCC solenoid WITHOUT taking the tranny out. In the following link is complete instructions on how to replace the TCC solenoid on the 3 speed tranny. Althou this is in a Pontiac Fiero, the same EXACT procedure applies to a A-Body car, except the A-body car is a slight bit easier to work on in this area.

http://www.kichline.com/chuck/fiero/TCC.htm

Other than the directions there, you will need the TCC solenoid, the one linked above somewhere, the tranny side pan gasket (or RTV if all else fails). You dont have do drain the tranny, and will loose maybe a 1/4 pint when you pull that tranny side pan off. I have done this repair befor, having never worked on a tranny befor. it took all of 90 mins to take it apart, and, put it back together.

[Tuddi]

Very glad to finally have gotten the culprit pointed out, and will now try and find a solenoid for the replacement and have this fixed ASAP.

Thanks for the great help!