[Gaz64]

Sounds like a universal joint.

I had a customers car (not a Cobra), that would go near solid intermittently.

I took the car home at one night because nobody could fault it.

Sure enough next day it did it to me, scary.

I found a coupling not far enough onto the rack which would put that next joint through too much angle.

Once fitted correctly, the joint was happy.

Lesson is, universal joints shouldn't go past 30 degrees.

Gary