I pulled my 4l60e out of my 70 gmc with the 5.3/4l60e combo for a rear main seal replacement. While it was out I put a corvette servo in it. I put the servo in because when I would really get on it it would not always hold 2nd gear. Anyhow, did rear main seal, installed trans back in and drove around maybe 100 miles. Noticed the tcc would engage and disengage quite a bit before it would hold. Checked fluid and it was good. Was driving along and lost 3-4 gears. 1,2 and reverse work fine. It acts like it shifts into 3rd gear but is like neutral. When I did the 5.3 swap around 8 years ago I did put new 3-4 clutches in trans. I would say they have maybe 10k on them. Would be 10k hard miles. Anyone have anything to check before I pull trans out and tear down?
4l60e no 3rd or 4th
- Thread starter classic70
- Start date
I'd double check your servo installation.
I put a corvette servo in the 4L60 in one of our farm trucks a long time ago and had the same problem. The split O ring on the 4th apply piston slipped out of the groove or something (installation error I guess) and gave me your exact symptoms. It was fine-ish for a short drive then not long after no 3rd or 4th, just like you said it was like shifting into neutral.
I put a corvette servo in the 4L60 in one of our farm trucks a long time ago and had the same problem. The split O ring on the 4th apply piston slipped out of the groove or something (installation error I guess) and gave me your exact symptoms. It was fine-ish for a short drive then not long after no 3rd or 4th, just like you said it was like shifting into neutral.
Did you check if it set any codes?
No codes
Check the 2nd & 4th Servos first, The back of the 2nd Servo is used as the 3-4 Clutch Accumulator (Which pushes the band off for the 2-3 shift).......
However, According to this unit's theory of operation, To get the Flare upon the 2-3 shift.....The Band is getting pushed off or the unit would just stay in 2nd. Meaning you at least have enough 3rd clutch pressure to push the band off.
*With the Band off & no 3-4 Clutch holding ability.....The unit is actually in 1st gear & is Overrunning on the Lo/Reverse Roller Clutch.
*If you were to rev the engine enough (Not recommended), It will pull again....So it's not technically in neutral.
Doesn't take much slip to burn the 3-4 clutch to the ground, Was the 3-4 clutch smoked when you tore the unit down?
However, According to this unit's theory of operation, To get the Flare upon the 2-3 shift.....The Band is getting pushed off or the unit would just stay in 2nd. Meaning you at least have enough 3rd clutch pressure to push the band off.
*With the Band off & no 3-4 Clutch holding ability.....The unit is actually in 1st gear & is Overrunning on the Lo/Reverse Roller Clutch.
*If you were to rev the engine enough (Not recommended), It will pull again....So it's not technically in neutral.
Doesn't take much slip to burn the 3-4 clutch to the ground, Was the 3-4 clutch smoked when you tore the unit down?
Common issue with aftermarket "Vette" Servos &/or Seals....But not necessarily a problem as you would have 2nd gear issues.
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