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Transmission bumps

My husband & I bought a used 1997 Saturn this summer, which we later discovered had a faulty, junk-yard-salvage transmission installed in it. That transmission was causing all kinds of problems, so we coughed up the $1300 to get a new transmission installed by a reputable mechanic, which came with a year warranty. Now it’s driving fine, but when we’re stopped at a stop light or have the car in neutral, the engine seems to “bump”. It is just a momentary feeling as if the engine is dropping into another gear. But when this happens, the RPMs don’t appear to change on the dashboard. It only happens once or twice a minute. Is this something to be concerned about? Could it be another transmission problem? Thanks!!

By “new transmission”, do you mean it is brand new? Newly manufactured? I guess this is possible, but this seems doubtful for a car of that era. I expect it also is a junkyard transmission that has been rebuilt by a transmission rebuild shop. Or it may simply be a transmission from another Saturn that was totalled by an insurance company put in w/out a rebuild. It wouldn’t be that unusual for a rebuilt xmission to have a few hick-ups. Suggest to return to the mechanic and get his opinion. It could be something as simple as needing a quick adjustment, or the fluid is under or over filled. And it is quite possible it has nothing to do w/the transmission at all, as it happens even when the car is in neutral. The engine may be simply be surging, which can be caused by quite of few things, often some kind of air leak which is confusing the engine computer’s calculation of the air/fuel mixture. One easy thing to do is check all the vacuum lines for breaks or leaks.