I have an 87 GXL with a new clutch (about 1000 miles) When I take my foot off the gas or put it back on the gas at low rpm's in first or second gear the car bucks violently. I have never noticed any clutch slipping. After having a leaky slave cylinder replaced, there is a little bit of chattering, but it is going away now. I am a little suspicious of the motor/tranny mounts, but I am not sure if that could cause so pronounced a bucking.

 

Don't hold me to this, however the clutch chatter and bucking are related. It is most often associated with getting grease or oil on the friction material of the clutch. It could also be that the flywheel surface is not perfectly flat, it could need to be resurfaced.

 

Chattering could be flywheel not resurfaced or a bad throwout bearing. The bucking could be the fliud on the clutch, or a broken differential mount. Any boom noise, or just chattering? Mine bucked till I adjusted the TPS, so that could be the problem as well.