Hello all,

My 1996 Accord had the transmission replaced around a year ago, still under warranty. Anyways, after I picked up the car from the transmission shop, it has had a heavier than usual engine or transmission vibration. The engine mounts and other mounts are all new or in still good shape. Anyways, the vibration only occurs in drive at idle. In neutral, the RPMs jump up a bit so the vibrations are less noticeable than usual. Same with the Park gear. There is no vibration or hesitation when accelerating or at any speed besides it at Idle. When at Idle and the AC turns on, the vibrations become even WORSE. Yes I know the compressor uses another belt that takes horsepower. But this amount of vibration is 100% abnormal. Before the transmission was replaced, the car idled fine, and when the AC was turned on, the car vibrated slightly. What could be the deal? I have a feeling it is something to do with the transmission but I am not sure. It is just embarrassing when I am in college and I take a girl out and the car vibrates like that lol. Thanks all in advance!

 

It could be when the transmission was replaced, the exhaust system was disturbed causing it to resonate at idle while in Drive.

 

Inspect the vac line going to the rear mount

 

Any check engine light on?

If idle speed dips below 500 rpm when load (AC) is added, the Idle Air Control Valve is not functioning to maintain rpm and vibration will be noticeable. Fix is to clean IACV inlet screen, valve movement, throttle body bore, and throttle plate (both sides).

good luck