Strange grrrrrrrrrinding noise

[Coyote_Rage]

4T60e stamped on the pan in a 91 GP.

Upon hard acceleration I get a very audible grinding/grating noise. Almost like a chain being dragged across sheetmetal. I have also noticed hard shifting when I am at or near WOT.

This trans has about 140K on it, and when I bought the car last year the trans fluid was brown, indicating lack of regular maint. I am prepared to buy a trans if I need to, but what in the hell is that noise?

[dohcfiend]

go manual. it is a PITA but worth it.

[IanSzgatti]

maybe it's lack of pressure causing incomplete engagement. planetary gearset worn out? pressure solenoid on it's way...

[gpse3400]

better check the fluid. if it has a hint of purple and or black, the trans is done.

[PCGUY112887]

4T60E in a 91? I thought they started 92-93?

[Coyote_Rage]

I thought they did to, but this one hase 4t60E stamped on the pan

[DEI37]

Is it a 3.4 or a 3.1?

[Coyote_Rage]

3.4L

[sharkey]

thats why. 91 was the first year for the 4t60e, only behind the 3.4l tdc. between 92 and 94 the 440t4/4t60 was phased out and the 4t60e took its place.

[TurboGTU]

Its probly the plastic thrust washer on the drive chain sproket that has seen its better days.

[nixtux]

when you idle can you feel a shudder every 15-30 seconds?

with the shudder comes a crazy quiet noise but not quite grinding?

I can't explain the sound but my Cutlass had a similar issue and 20 miles later momentum was taking me to my garage (thankfully I was able to make it since no gear would work.)

Ironically the idle was the biggest thing I noticed. But during traffic merges and whatnot it was like the car would shudder somewhat and it sounded kind of like grinding but not exactly.