Just once a day usually, just after the first time I start it, my transmission jerks into reverse quite hard. After that, any other time I put the car into reverse, it acts just fine. Any idea what's causing that. Do I need to have it diagnosed by a mechanic?
Transmission Problem - Jerks Into Reverse on 2000 Buick LeSabre
if it makes a clunk it may be your u joints easy fix.
About all you can do your self is check the fluid level. If the level is OK and the fluid looks OK on your 2000 Buick LeSabre the next step would be to scan the Power Train Control module for codes, the transmission pressure control solenoid should also be checked for proper operation.
Could be a bad Transmission mount.