I just bought a 1999 Grand Prix with 3.1L engine and 119K. I took it into our local trans shop to have them change the trans fluid and they told me that the fluid was very old and had not been changed in 50K to 75K miles and that it was sticky from age. They recommended that I not change the fluid and just wait until the trans dies then have it rebuilt.

The only reason I took it in for a fluid and filter change was because the trans does have a whine to it and because I always change the fluids in cars that I have just bought.

Anyway, I thought the advice was silly so I took the car to another trans shop and they pretty much said the same thing.

I have always assumed that new fluid with maybe a conditioner would be better than old trans fluid that has lost its detergent qualities and is contaminated with moisture and clutch/metal particles but then I may be very wrong.

I would like to keep the car for 2 to 3 years and put on another 30K before I sell it - what would you recommend?

Also, what do you guys think of the Mobil synthetic trans fluid for a trans with this much use on it?

the whining is probably a faulty PCS (pressure control solenoid) in the valve body. It's a fairly common issue on abused/high mileage GM transaxles. The advice to not do a fluid exchange/flush is sound. The new fluid is grippier than old fluid and could destroy your trans. IF the fluid smells burnt or is very dark brown, the damage is already done and new fluid (or a filter change) won't help a thing. If the fluid isn't burnt, you could try a filter change, and only replace the fluid drained from the pan. This will not shock the system like 100% new fluid would. Also, you put Seafoam/Trans-X or Lucas trans conditioner in at the same time to help clean out any varnish or deposits.