A Problem With Transmission

Hello,

I have had a problem with the transmission on my transport for a while. Whenever I went to see my mechanic he was not really willing to take a look on that.
Here is the problem:

Automatic transmit ion shifts to higher gear and then to overdrive smoothly and without any problem, but if the load increases, say I am on a slope and do not push the gas pedal, the transmission cannot shift from overdrive and I can feel the shudders while transmit ion is trying to shift form overdrive.

Any suggestion is welcomed.

Best Regards,

Mike

Hello,

I have had a problem with the transmission on my transport for a while. Whenever I went to see my mechanic he was not really willing to take a look on that.
Here is the problem:

Automatic transmit ion shifts to higher gear and then to overdrive smoothly and without any problem, but if the load increases, say I am on a slope and do not push the gas pedal, the transmission cannot shift from overdrive and I can feel the shudders while transmit ion is trying to shift form overdrive.

Any suggestion is welcomed.

Best Regards,

Mike


maybe the TCC isn't disengaging?

Excuse me for my indolence, but what is TCC?

Best Regards,

Mike

Excuse me for my indolence, but what is TCC?

Best Regards,

Mike

Torque Converter Clutch.

If you manually shift into 3rd under load, what happens?

If you manually shift into 3rd under load, what happens?

Thanks on your replies!
The transmission follows it. It goes to 3rd gear. If I put in 3rd and drive it goes nicely 1-2-3 and then if load increases back to 2 or 1. If I am in overdrive and switch to 3rd, the transmission as I said follows it, it goes to 3rd.


Best Regards,

Mike

Mike, would you please state model year and engine type.,,,well, if you have OD, it's either 3,8 or 3.4
...but, without any other details, I'd suspect transmission modulator.....in the years it is relevant....
...if you keep it in 3rd (D) then eventually, TCC does apply in 3rd gear. THis id felt as a slight jolt and rpm goes down 400-500 rpm....then if torque is increased, or a simple small kick on gaz pedal, it will jump out of TCC, still in 3rd, and rpm will go up 400 rpm...Can you verify that ? ....there are several cases of stuck TCC solenoids that have been reported on this forum...and sometimes, this will stall the engine when stopping at a taffic light...

I have had a stuck TCC solenoid - with the vehicle stalling at a stop light (3.8L, '95).

You can also test the TCC kick out if you're cruising at a constant speed in 3rd or 4th gear, tap on the brake with your left foot and it should kick out, RPMs rising a bit as the indication.

Everyone is ready to blame the poor transmission! By all means check those items - but what you describe is a driveability problem.
Start with the basics - tuneup, plugs, wires, check or change Oxygen sensor, MAF (mass air flow) sensor, clean injectors and throttle body ...

I don't have an answer to this but I have experienced it on a '94 Lumina APV with 3.8l. Best description I heard was "it feels like pulling a heavy trailer" coming to a hill - it just slows down as if lacking power. It felt like the computer is confused - it doesn't think there is a reason to unlock the converter and downshift.

I don't blame your mechanic - I had a tough time convincing GM it was a problem! It finally happened on a test drive. They did all the basic stuff Oxygen sensor, plugs/wires, MAF sensor, injector clean, scan test etc without much change. Tried a new chip, tried the "chuggle" chip- which basically unlocks the TCC/ downshifts as soon as the gas pedal is pressed. It did not solve the lack of power tho.
In the end - GM Tech claimed "they all do that" and stopped working on it.

Before this problem, I used to drive the van every day at varying speeds so I thought maybe something was sticking??

Anyway, to make a long story longer - I lived with it - it wasn't quite as bad..
Another problem (sticky IAC Idle Air Control Valve) was fixed by cleaning the throttle body and IAC Valve. It was a miracle :smile: the engine had power. Easily accelerated pas the 140Km/h limit on the speedo. Boy was I happy!!

But it didn't last. It got worse again last year - changed O2 sensor, MAF, Injector clean, throttle body and IAC valve clean, scan etc.
It did help reduce the "computer confusion" ie it does finally unlock the TCC and downshift - but it still has a gutless, restricted feel to it....

My theories are that a lot of low speed driving causes something to stick, deposits build up in the throttle body, intake, injectors, possibly converter and muffler - hence the improvement with throttle body cleaning.... , a plugged converter has been suggested too..

As an aside, the transmission was rebuilt (was stuck in 2nd) - no difference after.

I apologize Mike for posting this on your post - but I wonder if we have the same problem and can both benefit from the experts....

Thks,
Allan

Thanks Allan!

it doesn't think there is a reason to unlock the converter and downshift.

In my case it thinks there is a reason but it cannot do it. It tries, I feel shudders while it try to downshift but it simply does not happen. What I do is when I see a hill I accelerate so that the car does not want to reduce the gear.
I am still to do that test in 3rd gear. Will be done in a few days.

I think we are talking about the same thing. The shudder is because there is not enough power at that speed, and motor rpm. For me, around 80-100KM/H (50-60 mph). So hilly roads with 80-90kM/H limits are the worst!

I do the same thing - when coming to a hill, I accelerate to get the rpm's and speed up into a better range and build up some momentum!

..... when coming to a hill, I accelerate to get the rpm's and speed up into a better range and build up some momentum!
...and I shift to 3rd ahead of the hill long enough so that TCC applies in 3rd and except in extreme uphill, il will climb easily in 3TCC....or eventually TCC will unlock and that is a joltless change. I have no drivability problems (in this regard at least) at this time but I do that to avoid jerking....
..and while we are at it, long time ago the car would not want to accelerate rapidly..eventuakly it would, but long after I had tried to overtake that trailer truck and resolved to stay behind.. .....and to make a long story short :biggrin: the MAF sensor had accumulated a dirt deposit on the sensor wires..and that made it blind to rapid air flow changes..one Qtip and a few drops of alcohol later, all was back to normal....this after GM and others wanted to change fuel filter, fuel pump, injectors....you name it.
..so yes, as Allen says, there are lots of other symptoms that may feel like a transmission problem.
mmm..Mike, again, year and engine :confused:

Year and engine: I know it is 3.4l engine and for the year, it is 1996.

Best Regards,

TMN

LMP - Yes - I sometimes downshift to 3rd before a hill too.
We have a different definition for "drivability problems". I would consider having to downshift to 3rd to avoid jerking a drivability problem.
(I am almost tempted to say we have the same (or similar) problem - but I won't ...).

I have had this van since new and believe me it used to have no problem with hills when fully loaded. It is definitely down on power - and it has not been easy to find a reason. Then again, I mostly drive on flat express ways so it's only a problem on trips!!

I agree it's difficult to find good mechanics who don't just start changing parts.

Cleaning the MAF sensor is a good idea - mine had some crud on it but it didn't make a difference. I swapped another - no change. I think you were running without an air filter when the MAF got dirty???

I apologize to Teodora for sidetracking your post. Since mine is a '94, I will back out now. Good luck with it.

Allan

Hello!
Just registered and the first posting ...
Seems that our problem with our TS is near to the described by the starter of the thread - and I want to describe our prob as good as I'm able to with my little English:
If I drive the TS at around 70km/h (43.5Mls/h), the tach shows around 1600 rpm, with depressing the gas-pedal at 5 to 10% steady, the TS begins to wobbling, shaking, bucking. Sometimes more, sometimes less. If I depress the gas pedal more to accelerate, or with no gas, the wobbling etc. ends. I changed (to new ones) the ignition module, all three ignition coils, spark plug cables, spark plugs, TPS and the fuel filter. No effect. The only (subjective only, because the route I drove then was another as usual) effect I think was that after the battery was reconnected I didn't notice the wobbling etc. for around 25km (16Mls).
Anyone an idea?
Thanks!

P.S. Somewhere I read about shifting problems cause of bad grounds of shift solenoids. Someone out there who can tell me whre to find these grounds? Or at least where to find the right pages in the GM shop manual for the 1993 TS?