I have felt a slipping/clunking in first gear take offs on my 85gsl, i checked the drive shaft for play and it seems that i can turn the shaft about 3/4 inch in either direction, no visual signs of freeplay in the u-joint, it is not a wheel bearing kind of noise, its a definate gear/tooth slip feel/noise that seems to be only from the left rear area...... thoughts?

 

update:
my diff drain plug wasn't tight enough , i noticed fluid on plug, tightned it up checked fluid and it was only down about 5oz, added some and test drove, i did not hear the clunking during take off anymore,,could it being just a little low on fluid caused the noise,,,weird,,,,

 

What makes you think it is slipping?

Maybe the Limited Slip differencial plates etc are very worn.
Is this happening under hard acceleration or just normal launches.

 

theres a way to test the LSD clutch plates. jack up one side of the car but make sure the other side tire is still on the ground. put the car in gear. use a torque wrench one of the lugs starting from as low as the t-wrench will go and see how many foot pounds it takes to spin the wheel. the plates were so shot on the race car it would spin the diff. at 20 lb/ft. i forget exactly how much pressure should make it spin... i will look into it and post it if anyone wants me to.