Overdrive Problem?

[94LuminaZ34]

OK heres another thing wrong with my car. If i'm driving down the highway in overdrive and I give it gas it downshifts into third but doesnt come back into overdrive no matter what I do? I have to pull over and restart the car then it will drive normal. There were no codes when I scaned it. Any Ideas? Where should I start looking? I posred on another forum but know one has any ideas.

1994 Z34 Lumina 3.4L

[gpse3400]

Since you definatly have gears 1 to 3, we need to make sure that you are not confusing no 4th with the Torque Converter Clutch not locking up. When you notice this happening again try to stay at a steady speed, then give the engine alittle more gas. If the tach flares then its the TCC and since its a '94 I'm sure its the PWM soleniod which can be bypassed externally. If not then it could be more intense.

[Azrael]

Check your fluid level. I lost 4th and OD after losing ~1.5L of fluid to a slow but steady leak.

[94LuminaZ34]

Since you definatly have gears 1 to 3, we need to make sure that you are not confusing no 4th with the Torque Converter Clutch not locking up. When you notice this happening again try to stay at a steady speed, then give the engine alittle more gas. If the tach flares then its the TCC and since its a '94 I'm sure its the PWM soleniod which can be bypassed externally. If not then it could be more intense.

Yea it seems like when it happens if I give it gas the rpms go up like driving a standard, so does this mean its my TCC? What is the PWM solenoid?

[RedogOnyx]

I know older GM 4 bangers had a plug on the tranny that the soilnoid got the singal to lock and unlock. Try unpluging that

[gpse3400]

Taken to PM

[94LuminaZ34]

I tried unhooking the various wires from the plug on the trans today and SES light comes on and I go into third gear I think so I assume this is limp mode? I have a idea, can I just unhook the plug and wire in 194 bulbs to act as the solenoids so the psm thinks thats everythings ok? Will my trans still shift without pcm control or the solenoids working? The trans is a 4T60E

[gpse3400]

I wouldn't try that. Your computer may not like that.

[94LuminaZ34]

OK got some more info. I keep getting a code P0740 which is TCC circuit failure. Now when I drive it it will shift from third into lockup or fourth at about 55 mph and then 10 seconds later it will downshift into I think second and wont come back into third or fourth without a restart. It seems to do it everytime so I think I have to replace some solenoids what do you guys think? Also I have my abs and brake light on because of a code 51 which is rear abs motor freewheeling would that have anything to do with the trans?