4T60E Question

[GregGP]

Hello everyone. I am working on a friend's car and had a question about the transaxle. It's not a Grand Prix, but the Oldsmobile forum doesn't look like it has much traffic. Anyway, the car has been sitting for a couple of years, and now when he drives it, it shifts fine from first gear to second. Once it is in second gear, it just does not want to shift into third. If he gets the car going fast enough for long enough, it will finally shift, but I can't tell whether it is shifting into third or fourth. It is also getting a couple of DTC's; a code 21 and a code 39. The car is a '93 Oldsmobile 88 with a 3800 and the transaxle is a 4T60E .

[grog11]

If the car has sat for 2 yrs. the Transmission fluid probably has dirt that has settled in the valve body and is hanging up one of the valves in there along with obstructing passage ports. I would drop the pan, clean out the debris, and do a transmission fluid change with some Mobil 1 synthetic ATF. Change the trans.filter, then run it a bit and see if that synthetic fluid doesn't clean out some of the dirt pockets.

There are solenoids inside that transmission that shift the gears and they too may have alot of debris stuck on them stopping maybe the 2-3 shift cycle.You may have a bad solenoid or wiring problem. Do take off the neutral switch wiring connection and the wire harness plug that goes into the trans case, clean the connections and replug them in. They do get corroded sometimes stopping the signal to the solenoids.

The 4T60E 4th gear is really only the torque converter clutch lockup solenoid, so you have a 3 speed electronic controlled transmission with overdrive

[BNaylor]

Don't forget the 4T60E autotransaxle has a vacuum modulator to help control shifting and control line pressure versus the 4T65E which has a PCS. So check that out and the vacuum source.

[grog11]

The Vacuum Modulator may also be not working right, causing the hesitation. Good thought there BNaylor.

[Blue Bowtie]

grog offered a good suggestion. Drop the pan, clean up the debris, check the oil tubes, install a new filter, install a drain plug, and refill with clean oil. Be prepared to do this again in a few thousand miles (thus the drain plug).

Verifying the modulator vacuum source and adjustment of the modulator (some are adjustable) and verifying the transmission and range selector switch (neutral safety) electrical connectors would also be a good idea.

The Code 21 also needs to be corrected. Although the line pressure is controlled by vacuum (the modulator) the transmission is shifted electronically. Shift points are determined by the ECM calculated engine load (LV8) and this is reliant upon a good signal from the TPS. The TPS voltage being high will tend to hold off the shift since the ECM understands this to be a higher throttle angle. The 1-2 shift is also governed so that despite the throttle angle the trans will shift at a limited engine RPM.

The Code 39 indicates a failure in the TCC circuit, which is why I suggested checking the electrical connector at the trans.

Actually, the 4T60E has four complete GEARED drive ranges, one of them being a 0.67 overdrive, PLUS a torque converter lockup.

[GregGP]

Thanks guys! I forget, is there a throttle valve cable for this transaxle? or is it just controlled by vacuum and electronics?

[tblake]

If I'm not mistaken, the 93 4t60's still have a throttle boost cable.