Transmission on 2001 Pontiac Montana

I have a 2001 Montana with 140,000 miles on it. I bought it used five years ago. The transmission is going out. The shop did a scan and found the
torque converter clutch is sticking on. This is a foreign language to me. Can someone explain to me what this is?
Should I make the repairs or ditch the van? Good points: four new tires in December 2013; body is great; and minor maintenance repairs. Bad points: the air conditioning is broken and the heat is forever terrible (I live in Minnesota).
The van is currently at my regular shop and they do not do transmissions so I do not have an estimate or more information about the problem.
Thank you for your help!

Normally there is some slippage inside the torque converter. This is what allows the engine to be running and rotating in “Drive” while the wheels are not moving. But the slippage wastes mechanical energy. So when the car is moving at highway speeds, the torque converter clutch “locks” the mechanical parts of the torque converter together to eliminate the slippage and improve gas mileage. The clutch typically “locks up” automatically at about 45-50 mph and stays locked at higher speeds. It then unlocks when speed is reduced below that level. But if the clutch sticks and won’t unlock at lower speeds, the necessary slippage won’t occur and the transmission won’t function properly.

Only you can decide if the van is worth keeping. First you need an estimate. Take it to a good indepdendent transmission shop, NOT a chain shop. Replacing a torque converter clutch should be a fairly routine repair for a transmission shop, but it won’t be cheap because of the labor needed to remove and replace the transmission.

But if it were me, I’d pay to have it fixed and keep driving. The van isn’t that old and should have many miles left if the engine has been rmaintained.

I assume rocker panels are somewhat dull?

Try adding a can of Sea Foam Trans Tune to the transmission fluid.

Sometimes the solenoid valve for the torque converter clutch sticks from gum and varnish. I’ve had luck freeing up these solenoid valves using the Trans Tune.


What symptoms do you have? Has the transmission ever been serviced?

What were the specific error codes that were pulled from the computer? (They look like “P0123”). Ask your shop if their scanning equipment is able to retrieve GM-specific codes. GMs have a lot of codes that “hide” from many scanners and you really want to know that ALL error codes have been read.

If you take it to a transmission-specialty shop they are very likely to tell you that you need to have a complete rebuilt transmission installed, including a new torque converter. Figure on $3-5,000. I’ve owned one of those vans. At its mileage I’d be hesitant to buy a new tire for it, let alone a new transmission. As such, my own preferred last ditch effort would be Tester’s suggestion of the TransTune. I would still have a shop look at it first. But when they give you the $4,000 estimate, spend $10 in the transtune instead. If that doesn’t help, …well, I got about $350 for mine at a scrapyard.

To elaborate on jesmed’s description of the TCC, this van has a somewhat odd TCC function. It doesn’t just lock / unlock. It actually applies by percentage, so the TCC can gradually apply and be locked up by a certain percentage. This generates tons of heat (all the more reason that the fluid needs to be regularly serviced), so the TCC has a special lining to handle it. That whole thing makes the diagnosis of problems harder.

Wow, thank you so much for all of your help! I have a much better understanding of what is wrong with the transmission thanks to the replies on this discussion board! I went to two local auto parts stores to buy Sea Foam Tran Tune. Both stores were sold out so I bought Dr. Tranny’s Instant Shudder Fixx. I put it in my van last night and my van is running well today! It got me to and from work without problems.

I think this is a Band-Aid on a big problem, but at least it will give me some time to weigh my options: get rid of the van or fix the transmission. I appreciate the help you all offered on this discussion board.

Oh one other thing, on my way home from work today the “service engine soon” light went off. That was an unexpected surprise!

I will ask the repair shop if their scanner reads all codes, I wasn’t aware of the hidden GM codes. Those car manufacturers sure know how to keep themselves in business.

To answer other questions: The transmission has not been serviced before. I had the transmission fluid flushed as standard maintenance once since I’ve owned the vehicle (purchased in 2009 with 95k miles). I make repairs as needed and do maintenance regularly. The van runs well. The rocker panels, eh they are rusty but I’ve seen worse.

Tranny symptoms: on Saturday the van was seemingly fine when the service engine soon light came on. Within two miles the van started jerking a little bit. I drove it to the service shop for them to look at it. It is not a GM service shop. It is an independently owned shop where I’ve been going for about 4 years. They are nice men and I trust them.

Thank you for taking the time to help me with this!

@Lola, it’s entirely possibly that simply changing the tranmission fluid and filter will help. I once bought a used van that had a bad case of “torque converter clutch shudder” that was completely eliminated by simply changing the fluid and filter.

I would try that and the Trans Tune mentioned by Tester.

The shudder fix is a friction modifier - basically it changes how slippery the fluid is and thus how much the parts inside can slip relative to each other. (I don’t know if the shudder fix increases or decreases slip.) The problem is that all automatics have to have both to work correctly - the internal parts have to both slip and grip. The whole transmission as a system, including its fluid specifications and computer controls and all of its internal parts were engineered together to work as a system. And the friction coefficients of the fluid are very important. So, in other words you have just modified only one part of a complex system.

The point is, that even if it has alleviated some symptoms I would be worried about it in the medium to long term. My own approach (if I wasn’t going to rebuild) would be to go ahead and do the transtune. I’d probably put it in, drive it for 1000 miles or so, and then have the pan dropped and filter changed. I’d probably have a drain plug installed and do a couple more drain/refills at maybe the next two oil changes.

The thing that’s quite different about TransTune is that it isn’t a friction modifier, but a cleaner. I’m assuming by your text description (“found them torque converter clutch is sticking on”) that your code was P0742. One common cause is a gunky TCC solenoid (but there are others!) Cleaning gunky solenoids is what TransTune does (and the new fluid helps a ton too). The shudder fix doesn’t do that.

If I did the transtune and all of that and it still had the problem, then I’d go back to the shudder fix for as long as the thing would go.