OK so I just got my open headers fixed today and as a result can finally hear something other than the engine. But, I'm feeling and hearing a small jolt when I engage the clutch. Is this normal or am I just now noticing it now that I can hear it?

Is this when you let out the clutch pedal? Is the noise from the rear of the car.?

From a standing start? Every gear shift? Is the engine even running? An electrical jolt?

Just kidding. Diff mount is the first thing that comes to mind.

Every time I push in and let out the clutch, from the rear of the car. When I'm driving at a decent rpm and I'm not steadily accelerating and its doing the whole rocking back and forth thing it does it to. No problems under steady acceleration. My friends dad rode with me and thought it was the u joints.

Diff clunk is very common. Diff mounts, Universal joints -

Yup definently check your u joints...... don't forget to check the half axels either. I just had the same problem. Also before you order u joints thinking its no big deal bc you have done them on other vehicles, make sure you can get them out. The u joints are supposedly "non-replaceable". I personaly couldn't remove mine, luckly the car came with a spare set of half axles. maybe some of the more experienced guys here have some advise on the supposed non-relaceable u joint.s

Edited January 28, 201213 yr by 77_FairladyZ

The half-shaft u-joints are replaceable on all years. The joints are not like US joints though, with a retaining clip on the outside of the bearing cup. The retaining clips are on the inside, riding in a groove in the cup. Some people miss that and try to force them out, destroying the yoke in the process. The clips will fly out, seeking eyeballs or distance when removed.

The 240Z and early 260Z u-joints are replaceable in the propeller shaft (what Nissan calls the main drive-shaft). They went to the staked in u-joints for the stout-bodied, big bumper cars apparently. I might be off on the years, but I know the early ones were replaceable.

It would be worthwhile to crawl under the car with a strong light and a screwdriver and pry the joints around. It's hard to see a loose one otherwise. Look for dry seals and rust around the edge of the bearing cup. The Nissan joints are very well made and very tight and will last a long time unless they dry out. An old Nissan joint is probably better than a new aftermarket joint, in my opinion. There are six u-joints total, so a full replacement of all can be expensive.

While you're under there, get some leverage under the nose of the diff and see how far up you can move it. If it 's easy to move around, it's probably bad. After 40 years, it's probably bad anyway.

Edited January 28, 201213 yr by Zed Head

Just because you said you fixed the "open header", check the exhaust pipe(s) to make sure that its not hitting the body under side when the motor torques.