Hi..this is my first post, though I read this forum almost daily.

I need help diagnosing a resonating whining noise on my 95.5 Rodeo with an automatic transmission and 68k miles on the odometer. It occurs around the 2000 rpm mark (where the transmission normally shifts to the next gear). There is no whine before it reaches this mark and the noise disappears beyond this point. The whining occurs in any gear and even when the car isn't moving (sitting in neutral or park and revving engine). It is a high pitched sound that has some resonance and a slight vibration.

this problem occurred after I brought my truck in to the dealer for some work. The starter, timing belt, waterpump, tensioner, valve cover gasket were replace. Also a 60k mile service was done. This includes a transmission flush, among other things. I'm worried that the transmission flush may have done some damage here. (I know I should bring it back to them to let them deal with it, but it is hard to prove that they did something wrong)

I've since had a mechanic drop the transmission pan and replace the filter, but this didn't help. I tried adding lubegard red to no avail. Is this whine most likely from the transmission or the torque convertor? Could it be something in the engine instead? Suggestions?

BTW, I tend to baby my vehicles so the car is well maintained from birth. The transmission was flushed before at 30k miles. The fluid always looked good between flushes.