My friend has a 91 accord AT ex but is having transmission vibration problem.

Whenever he switches it from park to reverse it will make this vibration and car starts shaking a little bit. It happens as he still holds the brake after the reverse switch over.

However, after he will apply the gas and go reverse the problem will go away.

This doesn't happen on drive or anywhere just during reverse only.

What could be the problem?

 

I'm going to go with a broken either front or rear engine mounts. Check them to see if they are cracked. Cuz the rear of the engine tilts down when you put it into drive and tilts up when the engine is put into reverse...