Travu25

Today I was driving home, and I was merging on the interstate. The car in front of me was taking its good ol' time merging so i stomped it to go around him, and all of a sudden the cars RPM's shot all the way up as if i was in Neutral. Then it caught? What could be the cause of this?

mrvedit

I assume then that the trans also downshifted into 3rd?
This would then sound like a slipping 3/4 clutch, the weak spot of a 4L60E.
This can be caused by "normal" wear on the 3/4 clutch and/or fluid pressure leakage on the way to the 3/4 clutch.

If it did not downshift, it could of course still be the 3/4 clutch, but could also be band slippage, possibly due to a leak in the servo area. This thread is similar:
https://ls1tech.com/forums/automatic...h-gear-od.html

I think its time to start saving up money for a rebuild with performance parts.

Travu25

i was going about 45 so i think it might have been 2nd

guy7bmwm83

iTrader: (5)

Mine has been doing something similar. In O/D, I will mash the gas and it seems to hesitate for a second or two, then I feel/hear a thud and it continues accelerating. I haven't noticed the rpm's shooting up like yours. I recently had the differential rebuilt and continues to do this. So it's most likely the transmission. My car has 156,xxx miles, but don't know if the transmission has ever been rebuilt.

mrvedit

The only way 2nd gear can slip is for the band to slip.* The band is controlled by the servo which has 4 seals in it. A leaking seal or a cracked piston in the servo will cause various shift problems, which can be intermittent. Of course, the band can also wear out and begin to slip.

Raising line pressure with a boost valve might extend the life of a partly worn band.

* A slipping forward spag would make all forward gears slip.

guy7bmwm83: I won't venture a guess for a trans with 156K miles on it. Technically it just sounds worn out.

Scottbennett42086

Mine 94 trans am 135xxx does something like this. But I can go from 1-2 then when it goes to bang 3 it just reves right up. I tried switching a-b shift solonds and still does the same thing. Any ideas?

mrvedit

Wear/slipping/failure of the 3/4 clutch is probably the most common problem with the 4L60E, especially older ones. It will quickly get worse so start saving for a rebuild.