4L60E Slipping

[excrider121]

98 T/A LS1 w/4L60E



Transmission was rebuilt two weeks ago. The transmission would "slip" out of OD after about 20 minutes of cruising. (I say "slip" because that's exactly how it feels. Anyone that has ever driven a manual knows what it feels like to give it too much gas w/o letting the clutch out all the way; the car revs, but doesn't pull like normal.) When the transmission would slip, you could manually put it in third or neutral, (stomping the gas to the floor wouldn't do anything but redline the engine, it wouldn't shift) then putting it back in drive would eliminate the problem.

When we had the transmission apart, there were a few burnt steels and clutches. The planet and sun gears all looked fine, minimal wear. Every clutch and steel that comes with the master rebuild kit was replaced. 3rd was toast. No abnormal metal shavings/gear fragments were found; just the usual metal powder. The transmission went back together easily, all clutches were soaked in Mobil 1 transmission fluid for a minimum of 10 minutes. We had no problems until we got to the four seals on the shaft for the forward drum. When we replaced them, we didn't realize that they had stretched a little and when we dropped the pump on the shaft, it sheared all four of them off. We replaced them with the old ones and wrapped the shaft with electrical tape for 20 minutes, and then the pump slid into place w/o problems. Just to double check, we removed the pump once more just to check, no seal damange.

The valve body was rebuilt, with all the springs being replaced, the 1-2 3-4 accum was ground down and the added stabilizer collar and spring were put in place. The reverse lock-out was ground down to decrease reverse-drive shift time. The old solenoids (all of them) were reused.

Transmission was assembled, and was driven error free for 2 weeks....until yesterday.



It has started slipping out of OD again. Only this time, when I downshift to 3rd, same problem, tranny feels like it's slipping.

I have two ideas as two what it could be. But before I start throwing money at it, I'd like to see what else you guys can come up with. I'll tell you after I get a few opinions what I think it could be, but I don't want to affect your ideas.



INB4 get an m6








Cliffs: Tranny slips, Tranny was rebuilt. Tranny STILL slips. Ideas?

[Cutlass]

did you replace the piston seals for the 3-4 clutch? Another fix I've heard of for repeat 3-4 clutch problem is a new or different input shaft/drum.

[excrider121]

Yep, replaced the seal. The input shaft and drum were clean as a whistle. If it wasn't covered in tranny fluid, I would have thought it was new.