Mustache Bar Bushings... Anything Special I Need To Know?

[Zed Head]

It's been posted occasionally that one-wheel burnouts are the death of a diff.  The hole for the spider gear pinion shafts wallows out.  I've seen pictures where the hole is so worn that you can see the ovality and the looseness of the shafts.  You might see something if you pop the cover.

 

Kind of confusing that the deeper you go in the diff, the more "pinions" there are...

[240260280z]

Front differential mount is usually the klunk cause.

[Zed Head]

Halfshafts are in good shape and have no joint play, driveshaft u joints are fine and tight, diff mount is just dandy and has no play. The limiting strap is still in place on the nose. My only guess is that there's slack in the diff. 

To Blue's point - it's hard to tell if the diff mount is really in good shape, when it's on the car.  The loose rubber is not obvious.  I think that the "clunk" is actually the sound of the diff dropping back down on to the crossmember and mount after the loose rubber lets it lift.  It doesn't have to lift far to make a noise when it drops back down.  The strap doesn't really come in to play.  I thought mine was fine, but once I replaced it, I stuck it in a vise and could pry the two pieces apart easily with a big screwdriver.  And there's actually a measurement you can make, shown in the Rear Suspension chapter, to help determine if the rubber is worn.

 

Also hard to tell if the u-joints are good without sticking a screwdriver in to the joint and reefing ti around while watching the seams of the seal with a strong light.  Twisting the half-shaft by hand won't really do it.  They see a lot more when in action.

[240260280z]

[71Nissan240Z]

I had the diff clunk pretty bad. The only thing that was saving it was the safety strap on top. The mount had completely separated into two peices. New one from nissan was around $50 if I remember correctly.

[madkaw]

The clunk can come from almost anything loose under there. The diff mounting nuts only have to be loose a half a turn and it will make noise.

Check everything and get rid of the strap and get something else-it's probably the cause

[metalmonkey47]

Wow thanks for all the information guys! I was just reading through Hybridz this morning on a long thread detailing some of this. I think my clunk is coming from quite a few places, unfortunately the output shaft on the transmission seems to have a little play, enough that it makes checking the u joints more difficult. Although, as cheap as they are I might just go ahead and replace them and have the driveshaft balanced. 

 

I also considered strapping my GoPro under the car pointing at the diff to watch it lift. 

Is it possible that jacking lightly on the nose of the diff might reveal any play? Or is that just a terrible idea, risking damaging an already worn mount? 


I'll check all the mount hardware, I never took the time to do that for some reason, but I'll take the time tomorrow morning. Blue, do you by chance have the P/N on that mount? I see a partial in that picture there. Not sure if you have a full picture or P/N. 

[siteunseen]

Sticker was never removed on mine.

 

[Zed Head]

Check the mounting points for cracks also.  The guys that do burn-outs typically like to bang gears too.

 

Be aware though, that the clunk will never go away completely.  The clunk was noted on road tests of brand new Z's, I have a compilation book of Road and Track articles that describes it.

 

I've tightened everything up on mine and still get a "thock" sound occasionally.  I know it's just noise though.  One way to gauge overall looseness is to wind the engine up, a little bit, not much is necessary, in a low gear, then let off the gas quickly.  All of the looseness will be used up when the throttle closes and you'll know more.  My drivetrain feels nice and tight but the gear lash still makes a noise now and then.  Don't go crazy if you try this though,  Going up and down at high RPM would put a lot of strain on the parts, especially if loose. 

[metalmonkey47]

Well I figured it out guys! 

 

The outer driver side halfshaft u-joint is wobbly. I checked it when the clunk started, but I suppose with all the issues I've had to deal with kind of masked it, and this probably just started recently here. FWIW, the front diff mount looks like it's been replaced recently. The rubber is nice and tight with no tears or rust on the plates. 

 

 

Can you buy halfshaft joints? Are they even re-buildable without a driveshaft shop working em over?? 

[240260280z]

you can easily change the u-joint yourself !

[metalmonkey47]

Fantastic! Any suggestions on where these can be located? Seems any parts store I've checked with either doesn't list them for the R180, or doesn't sell them at all. 

Do they differ between R160/180/200?