Title should read "rearend problem" not tranny problem. Sorry. 1969 427 car. Just reinstalled rebuilt engine and rebuilt M21 into car. I had installed the new throw out bearing incorrectly and had to remove and fix. Lesson learned- Read directions FIRST and then do the job!! Anyway, that all done, it was time for a test drive. No leaks, clutch (centerline) feels good, brakes all feelin' good. Next major (I think) problem is a bad bang when I get on the gas a little quick. Like there is some slop in the drivetrain. All u-joints look good. Does not "bang" when you accelerate slowly and evenly. Seems like a rear end problem to me. What do ya'll think? Just bought car in fall of last year and motor blew up 75 miles into trip home, so I can not honestly say whether this thud was present before the engine rebuild. With car jacked up off rear wheels, you can turn wheels approx. 2-3 inches before you can feel the resistance of rear end gears engaging. Really sounds like a worn out rear to me. Suggestions? Second ? and this is straight forward- When looking at the drivers side of a 427 at the oil filter area, there are two "ports" or holes for fittings just above oil filter. Which one is for the oil pressure gauge line and what is the intended use of the other one? Thanks for you help.

 

Look at the snubber bushing.