Mechanic_Chick

I'm brand new to yotatech but have used this site to answer many yota related questions in the past. I have a question of my own now. My grandpa has a 94 extra cab pickup 2wd with a 22re and an auto trans. It has recently taken to vibrating/shuddering pretty violently when putting it in reverse. Nothing else seems to be wrong except the timing is a bit off as well (didnt tell me exact specs of timing). His mechanic said it could be harmonic balancer, i was looking for a second opinion and perhaps suggestions on an easier way to replace the balancer. I would appreciate any advice i can get.