While driving will a high whinning sound shortly followed by a banging sound as the transmission changes gears. Then proceeds into a herky-jerky motion if you continue to keep driving. If you stop the car and turn off the engine for a few minutes and restart then the van will run fine for awhile. Had the same problem with a Pontaic Transport. In both cases the mechanics could not find the problem. Any help would be greatly appreciated.
Dave Geauvreau