300SD transmission

car has 331,000 miles, tranmission has 80,000 miles on it. last filter and fluid change was 7000 miles ago (including draining torque converter). i am using aamco dextron III fluid

Pull the vacuum line to the tranny and drive it. Does it flare now?

If so, then your vacuum control valve atop the IP needs to be calibrated or replaced.

Loud clunk on downshift, especially if it happens sometimes is a sign of not enough vacuum.

So, it sounds to me like you have too much vacuum sometimes and not enough at others. I'd check out your VCV and vacuum source.

thanks for the reply. it will flare with the vacuum line off too, but only when the fluid is still cold. i haven't checked the VCV valve yet, but i was thinking that because it only flares with the tranny fluid cold that the problem was not vacuum related (bad servo or piston). i'll check out the VCV and let ya'll know

It could be a vacuum leak. Check the hose which rises from the top of thevacuum pump on the front of the engine. It feeds an "H" shape rubber divider. remove the two hoses from the left side and plug the fitting with two wood golf tees.If the tranny shifts better and the car runs better, you hav a leak soomewhere. You won't hurt the car by bypassing the unnecessary plumbing.