While driving my 240z during ZCON I noticed more clunking coming from my driveline as I shifted.  I already have an RT diff mount installed so I looked at the transmission mount.  Using my adjustable safety stand I could move the transmission up and down and see the mount moving with it.  Based on the video I captured it looks like the mount is at the end of its service life.  I did some searching but could not find type of polyurethane replacement mount.  My 240z has a 5spd in it from a 1977 280z.  Should I just buy a rubber factory replacement or can a poly mount be used with some fabrication?

https://youtu.be/XTcd4uWs6Cs

My old mount didn't have much movement in it. A litle less than whats on your video. I noticed the difference when I sat it next to the new mount. It had sagged a lot over the years, which is probably what yours has done.

The original nissan mount are not cheap, but the quality is very good.

I would not go with PU bushing set-up. It will transfer a lot of engine noise/vibration.

http://www.courtesyparts.com/oe-nissan/11320n3000

Nissan calls that mount the rear engine mount.  It's the only thing that keeps the engine from titling forward when you hit the brakes.  I replaced mine with an Auitozone Duralast brand.  It made the shift lever feel more solid.  Definitely raised the back of the engine too, probably stopping some driveline vibration.  I've never seen a urethane replacement for that one, although there are replacements for the outer ones on the 280Z.  You don't have those on the 240Z.

Thanks guys!  Seeing that my car is all stock, I agree that going poly is a bit extreme.  I am honestly shocked of how expensive the Nissan mount is.  I checked Autozone and the mount they show is not correct.  A quick check on Ebay yielded the mount below.  It should be here on 7/10 so I will install it shortly after and see how it goes.  I will provide an update once I have it installed and put a few miles on it.

Mount I purchased on Ebay

Autozone mount

That's not the one I got.  You could go to the store and check it out.  The internet makes us all forget about the old days of walking into the store and looking at a part to see if it's right..  But eBay works too.

Sometimes I check the local weather at my computer when all I need to do is get up and go open the door...

It seems there are two style mounts that come up when looking for a 240z manual transmission mount.  The one listed on the AZ site with four threaded studs and then one with the single threaded stud.  I checked O'Reilly Auto Parts and NAPA as well, both of them show the same mount four stud mount.  Advance Auto Parts shows both mounts but they are ship to home only.  I will wait and see how the eBay mount looks and go from there.  

240Z world.  I wonder if one's an automatic mount and everyone is using the same stock photo.  Or maybe they had to switch when Photobucket screwed them over.  Autoplicity's picture seems right.

http://www.ebay.com/itm/Beck-Arnly-104-0828-Motor-and-Transmission-Mount-/361572098485?fits=Make%3ADatsun|Model%3A240Z&epid=76417723&hash=item542f6061b5:g:sE0AAOSwEzxYZ0s5&vxp=mtr

42 minutes ago, Zed Head said:

240Z world.  I wonder if one's an automatic mount and everyone is using the same stock photo.  Or maybe they had to switch when Photobucket screwed them over.  Autoplicity's picture seems right.

http://www.ebay.com/itm/Beck-Arnly-104-0828-Motor-and-Transmission-Mount-/361572098485?fits=Make%3ADatsun|Model%3A240Z&epid=76417723&hash=item542f6061b5:g:sE0AAOSwEzxYZ0s5&vxp=mtr

That looks like a front engine mount, not a transmission mount.  Is that the kind you bought for your transmission?

No.  You're right it's an engine mount.  Bad text in the eBay ad.  The part number is for an engine mount.  The eBay listing shows 70-73 240Z, but an engine mount should fit all S30's.  So that eBay listing is completely screwed up, sorry for the misdirection.  So many ways to go wrong on internet sales.

OReilly 104-0828 - http://www.oreillyauto.com/site/c/detail/BA00/1040828/02327.oap?year=1983&make=Nissan&model=280ZX&vi=1209406&ck=Search_02327_1209406_-1&pt=02327&ppt=C0019#compatibilityTab_

I bought the type that looks like yours but must have a different bolt pattern.  Good luck.

Good news, the Ebay transmission was exactly as described.  It is made by DEA products and seems to be a quality unit.  Once I had the old one out and placed it next to the new one, it was obvious the old mount was shot.  Installation was straight forward and drama-free.

 

Unfortunately on the test drive it did not cure the clunking I am getting at the rear.  When I am driving the car if I have built up some engine speed, 3500 - 4000rpm and quickly lift off the gas, I feel and hear the clunk.  Getting the same engine speed and slowly let off the gas, I do not hear or feel any clunk.  With the rear of the car on ramps so I can see how things look with the weight on the wheels, the bottom of the cone bushing in my RT diff mount is touching the top of the diff.  An examination of the bottom mount makes me think it is collapsed.  My only theory is if the bottom mount is broken it is allowing the nose of the diff to point down while accelerating, creating a gap in between the top of diff and the cone bushing.  Then when I let off the nose of the diff hits the cone bushing thus resulting in clunk.  In looking at the mustache bar bushings, it has newer bar stopper bushings but its hard to tell the condition of the bushings in the mustache bar itself.  What do you think my next move should be?  *My apologies for the low light pictures, it was hard to create a good amount of light under the car.

Edited July 11, 20177 yr by Hardway

My theory about the diff clunk has been that it's the diff mount metal dropping down and contacting the crossmember metal.  So, even though the snubber might stop the lift, it might not stop the compression downward.  I ran some tests when I had clunking, by stuffing pieces of rubber inner tube in to various areas.  One was to jam it in to the gap inside the mount, which will lift it and stop it from dropping.  If it works, you need a new mount, like the transmission mount.

The other cause of clunking is bad u-joints.

Worn u-joints also cause clunking. You could have a look at those...