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limiting front differential mount movement


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Hey Everyone!

Has anyone figured out a decent way to limit the movement on the snout of the differential? I know about the pinion snubber and JTR (I think) way of wrapping a cable around it.

The problem I'm having is on hard deceleration due to the larger U joint flange from the 280zx, it's hitting the swaybar. I thought about moving down the sway bar a bit but that doesn't really fix the problem and I don't want to go to a solid diff mount as I've heard the noise is just horrible. I also can't reverse mount the sway bar to the rear as I have a Camaro tank and that will get in the way.

 

Anyone come up with a way to modify the stock mount or modifying a solid mount to accept urethane bushings to limit both up and down movement on front snout of the diff?

 

Just an FYI, but I have a billet MS bar and urethane bushings there so I'm assuming that is limiting some movement already.

 

Thanks in advance!

Edited by whatnow123
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Why would you promote that over the RTZ style mount?  

 

The design is weaker -the diff still sits on the crossmember, the noise issue might be exaggerated but it's still more than the RTZ-style, plus the design flaw of stressing a very small area of the crossmember, possibly leading to fatigue cracking.  Why take a chance?

 

The OP's plans for the car would factor in.  If he has a fairly noisy car maybe solid is easy.  But if he has a quiet street cruiser the old diff howl could be a problem.  If he's drag-racing, fatigue could be a problem.  The RTZ-style just seems more logical.

Edited by NewZed
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Only problem with the RTZ mount is that depending on the place you buy it from and your year it may need slight modification (grinding off tabs in trans tunnel, drilling extra hole etc etc). Other then that I think it works great, and you can run another poly step bushing on the bottom mount to sandwich. I was  told solid mounting the front and not solid mounting the rear is a big no-no.

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That's a good point about the drive shaft angle.  The design that people are copying is for a V8 swap and lowers the nose if used with the GM transmission mount.  So it might have issues with the L6.  Seems like somebody would seize the opportunity and tweak the design.  If it's used as a snubber though, you keep the stock angle and stock mount, just avoiding the nose lift.

 

So, no obvious solutions.  They all have potential problems.

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seattlejester, on 11 Oct 2014 - 2:21 PM, said:seattlejester, on 11 Oct 2014 - 2:21 PM, said:

Only problem with the RTZ mount is that depending on the place you buy it from and your year it may need slight modification (grinding off tabs in trans tunnel, drilling extra hole etc etc). Other then that I think it works great, and you can run another poly step bushing on the bottom mount to sandwich. I was  told solid mounting the front and not solid mounting the rear is a big no-no.

 

I had read that in several posts before I did the poly U bushings in the rear and  the solid front mount.  Some Z builders have welded additional stiffeners to the front cross member and added material where the nose bolts to the cross member.   Search for some pictures of failed cross members. They tend to fatigue and crack along the sides of the mount

 

I suspect that a few hard launches and/or burnouts in a V8 Z would trash the cross member when using the solid mount.

 

I have been using stock cross members with the solid mount for years in both stock and V8 applications and haven't seen any stress cracks so far,  but I don't abuse them either.

Edited by Miles
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Noise issue is definitely exaggerated. I ran a solid aluminum diff mount for years and it barely registered in my mind. If your exhaust is any kind of loud, I would wager that a solid diff mount wouldn't bug you in the least.

Edited by Swami
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I now run the SW motorsport option on my R180. After repeated failures of my standard mount I went to the RT style mount but had vibration issues on track. I then switched to the SWM item, it's way over priced but is bullet proof, problem solved for good! It is cheaper if you provide a core but not by much. 

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Had a solid mount in my '73 Z for one lap around the block and it came out. The gear whine was way too loud for my taste and my Z isn't exactly quiet. Glad I did because I've since seen pictures on this site of front cross members torn up from using these. Eventually switched to the RT mount with the Energy Suspension poly GM trans mount above and nothing below. There's an exhaust hanger bracket welded to the tunnel that people partially cut away to make the RT mount fit, but it only takes a bit of hammering to recess it enough that the RT mount fits fine. No point potentially weakening the bracket unnecessarily.

 

I sanded the GM trans mount down to match the profile of the nose of the diff to apply the proper pre-load to the mount, and I shortened the supplied bolt that goes in from the top. it was a little too long and it was hitting the metal plate embedded into the poly. I suspect not sanding the mount and the too long bolt may be potential causes of the issues some people have had with this setup.

 

I had no way of checking the drive shaft angle, But I have a 240SX 5 speed with the shorter driveshaft, and if drive shaft angle was an issue, this setup should have exaggerated it. However, I haven't had any driveline vibration issues. 

 

This has been my setup for the last 7 years behind an L28 turbo. It's held up fine through mixed use of drag, road course and street driving. So, overall the RT mount is one of the few things I'm content to leave as is.

 

Nigel

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$460 IMO is too much, I am a Datsun owner after all. Hehe. I believe it's $380 if you ship them the crossmember.

 

I guess if I had just bought this mount first up then I would have come out on top, but the car has changed a lot over a short time. On the other side I can't see it failing for a very very long time so, if you break it down over ten years it's not that much.

 

I also ran the solid front mount and new urethane moustache bar rubbers. I did notice upon removal that it had deformed/mushroomed the bolt retaining hole 

Edited by Gareth. J.
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