[RICK LAKE]

gt40gordy Gordy From what you have said, there are a couple of things that come to light.
If the car is hard to push or drags when turning It could be the alignment or the posi rearend in the car. I don't know what rear is in the car but a Jag rear has it's limits of about 450/450 HP and Torque. This is on street tires that are harder that say a 300 wear. Burnt out and hole shots do the most damage to the rearend with soft tires. The drag is not the problem, the clunk is. You say it frees up after the clunk. Jack the car up and pull the rear cover. If it's a Jag rearend and older, It's the same as a Jeep dana 44. The other way it to clean both surfaces well and use RTV and allow to setup for 24 hours. I think you will find the problem once you remove the cover. You are looking at the teeth on the pinion and ring gear. Also any metal flakes in the fluid when you drain it. This is easy to do. If you can get a couple of pictures of the inspection this will help us also. Rick L. Ps my concern is the locking up and breaking free. This happens most of the time when a gear tooth is broken or a stub shaft bearing is coming apart. This stub shaft bearing I know about first hand. Rebuilt Jag rearend and it went 3 miles and destroyed a bearing. Rearend locked up in parking lot. Spun car out was only going 20 mph. No damage to any thing. ON the street a different story cold happen. Rick. Just want you and the car safe and have many more years of cruising and fun.