notatruews6

iTrader: (3)

Ive got a 99 trans am with the 4l60e, it has started to act up in 3rd and overdrive, in third the transmission seems to have a very bad vibration, overdrive just wants to slip. transmission only had 40k miles. The vibration is interminute it only seems to do it every once in a while. Any ideas whats going wrong?

performabuilt

iTrader: (25)

well lockup could cause a chatter vibration issue , but if you are slipping in fourth i would say the 3-4 clutch is going .

FLT

iTrader: (1)

I would have to say that the slipping in forth is the band not the 3-4 clutch. However the vibration sounds like a tcc issue. If you lightly apply the break pedal while in third, keeping constant pressure on the gas pedal, does the vibration go away? This will tell you that you have a tcc issue. Vince

performabuilt

iTrader: (25)

I said 3-4 clutch because he said it vibrates i 3rd and he made no reference to 2nd having any problem at all so I would guess 3-4 clutch is going bad hence vibration slip in third and since more strain slipping in fourth through the 3-4 frictions , but either are possible,And the lockup check in a good idea but i would say as before either way you will be going into it or replacing the unit based on the information you supplied.

02NHRAtransAm

iTrader: (17)

time for a rebuild, same thing happened to my 01 SS only 54k on the clock and lost the 3-4 clutches with no warning. They were there one second and werent the next. It sucked

performabuilt

iTrader: (25)

The factory 3-4 clutch set will not handle much abuse at all they were intended for normal driving with the engine stock and thats it,

notatruews6

iTrader: (3)

To add, the torque converter has been taking a long time to go into lockup. the vibration will go away in every gear but 3rd.

performabuilt

iTrader: (25)

Did you try the brake test that vince listed above?

notatruews6

iTrader: (3)

Yea, when i apply a small amount of break pressure, the vibration goes away.

performabuilt

iTrader: (25)

well you have a converter issue also then , with the slipping in fourth and the converter chatter, I would say your in the market to either rebuild or replace both ,

notatruews6

iTrader: (3)

Looks like ill be looking for a T56 Swap.

Thanks for your help.