ok there a loud thunk when i let out the clutch i think itys comin from the rear differential but im not sure any one know what iu should do?

i'll shoot off some simple causes, the guru's can rip through you for more details later:)

It can often be caused by just a worn diff mount or strap, allowing the diff to move a little, as obviously it it will as the amount of force applied on it varies.....

Or you may have my problem where the exhaust is resting next to the diff, and when you launch hard they bend apart before clanging together:) but i doubt you have a 3 inch exaust, and this only happened after putting the r200 in. but none of this helps you!

Personally, i'd say its just sitting a little loose, i when wepulled my r180 diff out, there were teeth lying at the bottom off the diff that had snapped off, and it still wasn't making any sounds! (just glad we got it off when we did)

Charles

my thunking from the rear came from work out half shafts...

they would be moving around and clunking...

still work.. but i dunno if there is a bushing there of something.. but its clunking

Check the outer passenger side half shaft u joint--good bet it's shot, and very loose...just jiggle the half shaft, and it should move if the u joint is worn out...pretty easy to just look at it as well...I have had a couple go out on me, and what happens is all the needle bearings fall out of 1 of the 4 joints on that u joint, causing the whole thing to fail....

Good luck on finding the problem.

thanks guys i didnt think you would reply so quikly

i really love my new car and i have been working on it non stop since i got it

i was having trouble finding the problem but i think its the u joints now

any ways thanks again

On my car it was the bushings on the Moustache Bar and the differential mount.

Glen

78 280Z

Front Diff mount is the most common cause.

Yep, on my car it was the front diff mount.

I have just a couple of things to add. To check the diff mount , an easy way is to put pressure under the diff it's self. Put a floor jack under it and raise it while watching the move ment . if there is upward movement before the car starts to rise , the mount is shot. When you look at the ujoints and twist the shafts , look closely at them and see if you can see any rust particles near the little rubber sealls by each of the ends. This also goes for the drive shaft. If you find one half shaft ujoint that is bad , replace them all . Other wise you will be doing it again in a short time . Gary

Would the same cause of the rear shift clunk hold true in the '75 280Z?

yep..

1970 - 1978 240Z's 260Z's and 280Z's...

just the 280Z's have a moustache bar.. but other than that.. same setup..

Would the same cause of the rear shift clunk hold true in the '75 280Z?

All 240Z's, 260Z's, and 280Z's have front Diff mounts, and the clunk is most often caused by the failure of this FRONT DIFF MOUNT. Other possible causes are the U-Joints, and/or Moustache bar bushings, but the most common cause is the FRONT DIFF MOUNT. It is a notorious and very well known weak link in the system. Those of us who have worked on 240Z's for 30+ years have seen it many times.

yep..

1970 - 1978 240Z's 260Z's and 280Z's...

just the 280Z's have a moustache bar.. but other than that.. same setup..

NO, ......240Z's and 260Z's have ALWAYS had moustache bars. The ones on 280Z's may be different, but 280Z's aren't the only Z's to have moustache bars.