thump and hard jerk in transmission
My Saturn SL-2 with 42,000 miles (I purchased extended warranty from dealer) started shifting hard and at one point jerked so hard I thought I had been hit in rear end. Took it to dealer and of course this is not a consistent problem and they couln't find anything wrong. Very frustrating as vehicle is still doing this (not consistently) It seems to happen more frequently in heavy traffic and stop and go situations. I'm back to the dealer next week and in meantime feel very uncomfortable driving the car. Automatic transmission and seems to be worse from 1st to 2nd, but not good from 2nd to 3rd. Have driven today and shifts smoothly. But tomorrow who knows- please help - I think the dealer thinks I'm imagining this!!
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Can you find out if the tranny has been previously rebuilt? If yes, it's possible that whoever rebuilt put in a shift kit - which increases the pressure and makes that shift from 1st to 2nd more pronounced. If so, this isn't necessarily a bad thing (just off-putting to most) and could in fact mean that your tranny might last longer.
P.S. watch for your motor mounts - very hard, jerking shifts could weaken or break your motor mounts. Get this problem check out sooner rather than later.
The culprit was a worn modulating valve in the valve body of the transmission. Seems GM used the wrong material for the (sliding-spool) valve, and the valve would become oval (instead of round) over time. (According to the GM service adviser, the valve moves very fast while in operation, so I can understand how a bad material choice could wear out prematurely.) This would allow fluid (especially hot fluid - less viscous) to leak past and screw up the pressure for the upshift. Thus, it would "slam". The solution was to replace the valve body.
Maybe since Saturn is a GM company they used the same brillant design in the Saturn tranny? Hmmm... after all, why are they "general" motors???
Hope this helps.