Mystery clunk

[rcb280z]

classiczcars people! jalexquijano has resurrected this thread, from dead.  The last post was October 2012 before he began resuscitation.  ~2.75 years ago.

WOW! usually I notice that. Anyway....

[jalexquijano]

On ‎08‎/‎04‎/‎2015 at 0:18 AM, EuroDat said:

jalexquijano, I think you should be checking all the bolts are tight and the diff mount for starters. If the diff mount is old it will sag and cause these kind of noises. The two big nuts on the back of the diff cover often cause this noise.

Mechanic says the clunk is produced here at the half shaft joint. My car has a 280z 5 speed manual transmission.  Sincé we are here i would like to know which type of differential mount shall i order and which half shaft? Apparently there is some play here!

[Zed Head]

That's the propeller shaft, not half-shaft.  Did he mean the u-joints, or the differential mount?  The u-joints look kind of dry.  If you have a pre-74 shaft they're replaceable.

 

[jalexquijano]

He says the differential mount and the u-joints! Do you recommend OEM Nissan? If so please point out where to order! This clunk at first gear is driving me nuts!

[EuroDat]

I would use the original OEM u-joints because they come with different sizes circlips. That way you can set the tolerances correctly. A loose (end play) u-joint with cause vibrations. Remember a propeller shaft turns a lot faster than the half shafts.

Like Zed Head mentioned, you have the early pre 74 propeller shaft with replacable u-joints. You can tell by the large diameter cups and there are no burrs on the outside to hold the cup in place. You should see a circlip on the inside. They also look like after market, judging by the shape of the end cap. You can find the OEM part numbers for the circlips on www.carpartsmanual.com under the 240Z drivetrain section.

The circlips only cost less than 20 cents IIRC. Less than $10 and you have enough combinations for both u-joints. Make sure you use the same circlip on opposite sides of the u-joint or you will create an unbalance situation.

The original diff mount is still available. I would use the OEM.

Is he saying the the u-joints and the diff mount are causing the problem? Or is it the diff mount and while you are at it, the u-joints look like they could do with replacing.

[bartsscooterservice]

It's the diff mount, it was just not that solid, the diff has some room for play when the propeller shaft releases the torque on it. New OEM can solve it for some time, but it will come back. I replaced mine not so recently, including all the shafts, and it has come back again ( not all the time ). Maybe some aftermarket reinforcement brackets for the diff are a good idea. That thing needs to be rock solid in the chassis.

[jalexquijano]

I just ordered a NIssan OEM differential mount part number 55415-N4301 for my 1972 240z made in Jan 1972:

http://www.ebay.com/itm/1972-1978-Nissan-240Z-260Z-280Z-Rear-Differential-Mount-Insulator-OEM-NEW-/191579574506

Should i still order something else while i am at fixing the clunk? The car will be lifted and i want to eliminate all possible causes