Anyone a automotive tech? Need help with TH125 tranny

[hrc200x]

I can't afford to have my work car down since it gets 30mpg and my back up vehicle is a diesel pickup that gets 16mpg, and diesel here is 3.47/gal.

I'm wondering if there is a drain for the torque converter on a TH125 tranny? The tranny is in a '85 Buick Century, front wheel drive, 4 cyclinder motor. The owners manual mentions somthing about if you have the converter off or if you drain it it might take more than the 4 quarts of oil that it takes if you just drain the pan.


The past week it has been shifting strangly. Hard first to 2nd shifts, seems like when the torque converter locks up its almost like it gets stuck inbetween lock and unlock and the whole car starts shaking, let off the throttle a bit and its fine. Try kicking down the throttle when in lockup or D and it almost sounds like tranny slipping, then it down shifts. This was early in the week.

Later in the week it wouldn't shift out of 2nd gear when warm, and the last day before parking it, it wouldn't go out of 1st gear. Try it the next day when tranny cold it would shift into D, but hang in gear too long before it would shift.

Today I replaced the filter and fluid, fluid looked almost brown color which can't be good, but it has been like this for 7 years or so, and when I replaced it a few years ago it turned brown almost right away. There was also a plastic looking thing in the pan. I'd say a large washer, maybe about as big as the outside of a golf ball. It had 4 or so tabs on it sticking upward.

After the filter/fluid change the shifting seems fine, doesn't hang in gear any more before it shifts. Never did lock up, but I only went maybe 3 or 4 miles.

Just would like to know if there is a drain for the converter so I can maybe stop this cleaner oil from turning brown right away. Is there any good automotive forums out there for cars, kinda like what 3ww is for 3 wheelers. Have tried a search, but just can't find the right one.

[Mosh]

I rebuilt trannies for GM so I might be able to help.The washer in the pan dont sound good.Was it white,or tan in color?(the washer?)That is a thrust washer and if that spit out,then something is coming apart.

There is no drain in the converter.

The only easy thing I can tell you too check is the kickdown cable.It comes off the throttle body,and then,Goes down to the top of the trans and is held in by (1) -10mm bolt.
The cable could be hanging up,cuasing late and harsh shifts.You want to make sure that isnt sticking.
They can also be adjusted too.There is a clip on the cable(if i remeber correctly,it will be near the throttle body).You release the clip(push in on it) then pull the housing back,to its stop.Then get in the car with the engine off, and floor the throttle to adjust it.

Try unplugging the blue conector in front of the trans(that is your overdrive lock-up)It will not go into lock-up.It may buy you some time.And it may solve the bad chugging in O/D for a while.

Try adjusting the detent cable.

But in all honesty,I think she is on her way out.

[350Xhilaration]

Not sure about the blue connector, but the 125 only had 1,2,3 and no OD. The 440 had OD.

Also not sure about the washer you found.

To clean out as much of the nasty oil, you can "flush" the system by unhooking the trans cooler line from the radiator and rig up a hose to dump the fluid as you pour new fluid in as the car runs. Preferably this should be done with clear tubing so you can watch the color change. When it's all clean red fluid, you're done. You'd have to research direction of the flow (which cooler line to run into the oil drain pan) as it's been about a decade since I was a mechanic and even longer since I worked for GM.

You may not even want to do this until you figure out what the washer is. I know there is generally a magnet in the bottom of the pan, but not a white washer.

Good luck. See if MAX has any suggestions also.

[cr480r]

Those th125's are nearly bulletproof... I put 200,000 teenage miles on a '89 century after inheriting it from my grandmother... It became no stranger to burnouts, neutral-drops, and full throttle runs from every stoplight. Mine started acting similar to yours towards the end of its life... Eventually 2nd and 3rd gear would disapear after 20-25 miles of driving... then re-appear after cooling off for a couple hours... It always had 1st gear.. and the upper gears never slipped... They either worked or they didnt...

[fivepointfivesi]

edited for lack of comprensive reading in the orginal post, sorry. has it ever died when comming to a stop, like a manual trans when you forget to push in the clutch?

[hrc200x]

nope, never died when comming to a stop, once in awhile shifting into reverse it dies, very rarely.

Its funny how a bad TPS 3 or 4 years ago almost had these same symptoms, I bought a new TPS and installed it a few days ago cause I was sure that was the problem since I put in a used TPS the first time.

Yes, this tranny is only a 3 speed. But the lock up makes it sound like there is an OD, so not sure if this would have a blue wire or not?

I'll have to check the kickdown, it is probably out of adjustment, hopfully thats not what caused the tranny to go bad.

How hard would this tranny be to replace?

[Erics350x]

Are you sure that "washer" wasn't the pan magnet?

[Mosh]

I never meant to get too technical in my first post That is why I used a general description.But here goes.
I have had many of these things down and rebuilt.The white washer is probably your thrust washer for the drive sprocket in the trans.The Drive sprocket support bearing, is probaly going out,and the sprocket cocked and ripped the plastic washer. Hence why when it goes into lock-up it chuggles,beacuase it is starting to rip the turbine seals and you are losing fluid pressure to the converter.That sprocket is located behind the torque converter.
I know the 125 is a 3 speed with Lockup torque converter.
I never meant to imply it was a 4 speed.
On the 125,they used a solenoid to lock-up the converter.It is a blue conector in front of the trans,just behind the cooling fan.Unplug that.The trans will still shift normal(if the trans is good)but you lose the lock-up in the converter and will lose a little fuel mileage.Most of the time,the solenoid failed and would cause stalling when coming to a stop(like the one guy said)then release when cooled off.I have seen them cuase a few other problems.That is why I suggested unplugging it.

Like I said before,in all honesty,when you have thrust washers laying in the pan,things are coming apart,and at best,you are on borrowed time.
The detent cable MAY help,although I doubt it will.

With that being said,as far as replacment,You have to drop the engine cradle(frame),while supporting the engine,with a fixture.It is not a do in the driveway on your back job,unless you are really determined to save money.
Most boneyards sell 125 trannies for around 2-300 bucks.
A shop would probably charge you about 8 hours labor to do the job,which would be around 400 bucks labor.

On a trans, once things start slipping,and not shifting,it is almost never a fluid problem.Flushing will not help at that point,and On a high mileage trans with very dirty fluid,in most cases will only make the problem worse.But if you want to flush it completely,350xhilartions suggestion would work.Most shops will hook up a machine and flush 16 quarts thru it for around 79.95.Once you buy all the atf and do it yourself,It is almost the same cost to have them flush it.

You could PM MAX he does work at a stellar trannie shop.