95 lumina w/4t60e having trouble

[gacowboy30]

I recently bought this 95 lumina from my parents and it has 120,000 miles on it. The problem we have is when its in overdrive and drops out to pull a hill, sometimes once its back on level road it doesnt shift back up to overdrive. Its only done this 3 times over the past week. I asked my dad if he ever had it serviced and he said no, so I was planning on changing the filter and fluid at the very least. The fluid level is fine, still red, doesnt smell burnt, but did have little gritty particles in it when I wiped it off to check it (which may be normal for a tranny with this many miles). I just wanted to see if there is anything else that may cause this that I should look into, or will the fluid and filter change take care of it ya think?

[sharkey]

fluid and filter wont fix it. first id get a scanner on it and watch the data stream to see if 4th is being comanded. the pcm may not be commanding 4th gear. if this is the case, its a problem with one of the inputs. if it is commanding 4th, id suspect internal problems.

[gacowboy30]

I have a correction to make about my first post. It's actually not shifting out of 3rd gear when it does this, not 4th to overdrive like I originally thought. Just thought I would correct that info to see if it may be something else before I take it to be scanned. BTW, whats a ballpark price to be charged for scanning the tranny? Never had this done before.

[gpse3400]

the shift program goes 1-2-3-LockUp-4. thats upshift pattern on acceleration.

[gacowboy30]

Thanks gpse3400, I didnt realize converter lockup came in before 4th gear. Thats interesting.....Im not savvy with trannys so is this a computer controlled action, pressure, vacuum or a combination? Im not sure what causes this to go away for days and then suddenly reappear because all I have to do is stop the car, shut it off and crank it right back up and its fine. I guess it could be computer IF it is reset by shutting off the car or pressure IF something is clogging a passageway somewhere inside. Am I on the right train of thought or is it more complicated than that?

[Rhedalert]

well my observation is I won't see lockup in OD until after 4th gear is engaged. If I manually hold 3rd gear, it WILL apply the torque converter clutch, but as soon as I shift to 4th manually, the PCM releases the clutch for the shift, then reapplies it. My older cars never did this, so it's something maybe GM changed around '94 or so.

[gpse3400]

yeah Brian that might be. But I know for sure that '93 down lock up is prior to 4th. Moreover if I hold Drive, the TCC will engage as it should and if I manually upshift to OD the TCC will not release.

Yeah the TCC is electronically controlled and being in the eniviornment that the solineiod is in, it might be prone to intermitant failure. Now when the TCC enguages it'll lock the halves of the torque converter to one another thus eliminating all slippage. It will have te characterstic of an manual. you can test this after third gear applies by trying to accelerate lighily and noting the tach if it flares minutely. if it doesnt asnd the engine basically lugs you are in lock up. One othet tihng In lock up the engine will stay at a steady speed at cruise.

Id say if you are having a tcc failure, its mostlike the soilenoids. The TCC and the PWM soilenoids. I reoccomen replacent. It'll requre remoavle of the side cover and if you deceide to embark on this task, you many as well relace all the soleniods with genuine GM parts. The solenoids are cheap though te pwm might cost you alittle more 3 soilenoids A,B,TCC(which are the same) and the PWM. You also have a thermosensor as well. Now my friend Brian who just chimed in earlier has a tried to dissconnect the PWM solenoid and ended the malfunction of the tcc not engageing. But alittle harder, not much harder just alittle harder. You can try this by disconeecting/ removing the pwm wire.

[pontiac3100]

hmm so the t/c locks before 4th gear....that explains why the rpms go down more....