Rear suspension advice requested

[doradox]

Most of the studs in the rear diff covers are just that, Studs. And can be replaced with longer ones. You can do that and instal a 1/8" rubber pad between the diff and mustache bar. Should dampen a little noise. Just a thought.

Dave

You will be in for some big trouble if you use rubber washers on the diff studs. You won't be able to torque the nuts to the proper value as it will squeeze out the rubber and leave the diff rocking on the studs. The mustache bar and diff must have a solid connection.

Steve

[MEZZZ]

You will be in for some big trouble if you use rubber washers on the diff studs. You won't be able to torque the nuts to the proper value as it will squeeze out the rubber and leave the diff rocking on the studs. The mustache bar and diff must have a solid connection.

Steve

Thanks Steve, it was just a thought on reducing the noise, I wondered if it might affect things. I am testing the car without any interior as well and should figure that in. Hopefully, once I get in the Dynamat and carpet it will reduce it.

thanks

[MEZZZ]

I got the car back up on stands and took a couple photos. I think the problem is the driveshaft is hitting the rear sway bar. I took it for another test drive and it makes the noise when I downshift and apply the brakes at about 30-35 mph. It is hard to describe the noise, a metallic, very fast, chattering. I am thinking it is the driveshaft spinning and hitting up against the sway bar.

I took a feeler guage and I have about .025 to .030 clearance between the driveshaft flange and the top of the sway bar. I have E/S poly on everything. I really had to work to get the bushings for the rear sway into place, greasing them up and using a floor jack to get them squeezed into place.

As stated before, I am using the GM poly tranny mount method without the stock lower diff mount. I didnt shave anything off the mount. Everything lined right up (the bolt into the GM mount) and I tightened it up and it is touching the top of the diff. case.

Any ideas on where to go from here? Dave? Anyone. I am thinking I should have more clearance than I have between the sway bar. Thanks!

[geezer]

It appears the easiest solution would be creating more clearance between the swaybar and the driveshaft. I think I would try unbolting the mustache bar, lower it, remove the large rubberized washers and place two adequately sized washers/spacers inbetween the frame and rubberized washers. A few taps with a hammer & chisel will remove them. Possibly an additional washer on the GM mount would help create more clearance also. This is just what came to mind reading this thread, I haven't experienced the problem but I am using an R200 Diff in my 240Z which is configured exactly as you have in your pic.

[MEZZZ]

It appears the easiest solution would be creating more clearance between the swaybar and the driveshaft. I think I would try unbolting the mustache bar, lower it, remove the large rubberized washers and place two adequately sized washers/spacers inbetween the frame and rubberized washers. A few taps with a hammer & chisel will remove them. Possibly an additional washer on the GM mount would help create more clearance also. This is just what came to mind reading this thread, I haven't experienced the problem but I am using an R200 Diff in my 240Z which is configured exactly as you have in your pic.

Thanks Ron. I am using the E/S poly on the mustache bar, I dont have the rubber washers any longer. I do agree with you that getting some more clearance would probably solve the problem. I need to move the differential up. I am thinking I could do this by shaving some of the GM poly mount if possible, other than that, I am clueless.

If I elongate the holes in the R/T Mount, I could get it to raise up but I would question if it would slip back down over time. I just have to wonder if I am missing something? I havent found any threads of anyone else having an issue with the mount and clearance.

Another day, its family fun time Have to keep the peace you know.

[geezer]

I need to move the differential up.

Ahha, I understand now. Not meaning to critique the R/T mount, but it seems that there is still room for improvements in the design that would allow for a small amount of adjustability, without flipping it around or elongating the hole, maybe?

Edit: Just an observation; I have a 23mm rear sway bar that was taken from a '74 FairladyZ. It shows evidence of the driveshaft not having enough clearance also. So, this was an occurance with the stock diff mounts as well, for some models anyhow.

Edited August 29, 2010 by geezer
added info.

[Zs-ondabrain]

Well, at this point, I would just order or find another stock diff mount, toss the GM poly mount, bolt up the bump stop and go from there. These are all bolt in items so there is no modifying things to make it fit correctly, other than the shaving of 3/4" from the bump stop.

The GM mount drops the diff a little so this is likely causing the issue's you're seeing. I apologize for the inconveniances you've dealt with thus far. Urethane is GOING TO transfer more sound than rubber, it's just a fact of life. And not every application is the same. the differences between 240's, 260's and 280's, coupled with the differences in diffs give multiple options, lengths, depths problems, etc etc. So you've obviously found an option or 2 that does not work.

Elongating the mounting holes of the R/T is an option but raising it can also interfere with the E-Brake assembly, that sits just above the R/T. So it looks like the Bump stop may be the only real option at this time.

But on the bright side, you now know how to R&R a Diff better than most....

Dave

[MEZZZ]

Ron, not sure with the Fairlady but I had no issues before. All I know it was a P.I.T.A to get that stabilzer bar back in place. Trying to get everything lined up, squeezed in and held together while tightening it all up was a job for an octopus.

Dave, I was afraid you would say that. On the brihgt side, I am already TOO familiar with this part of the rebuild. It took me 3-4 attempts before it lined up last time, thats why I am not looking forward to doing it again.

No big deal, whats some more $$ and alot of time thrown into this car. I am sure I will like the R/T mount very much the 5th time I put it in, Im growing kind of fond of it I just wish I had known ahead of time, I dont ever remember anyone bring this issue up before. Regardless, thanks for the advice, might be awhile before I get to it, I just ordered all new cabinets, granite countertops, S/S appliances, travertine tile, etc.. for a kitchen remodel in an attempt to keep Mrs. Mezzz happy for a few hours Of course, I am doing all labor myself, not time after next week to work on the Z.

Thanks again guys, I will let you all know the outcome of this.

[Zed Head]

Howdy MEZZZ, I was just searching the site for some feedback on the effects of using urethane inner bushings on the rear control arms (transverse links) and this thread popped up. I've been changing bushings one system at a time and don't know if I want to do the inner bushings or not, since my rubber ones are still in pretty good shape.

How did your mod to the R/T mount turn out? How is the gear noise and how is the ride with urethane bushings all around?

[tlorber]

I have a condition similar to that stated above, where if I use the GM Tranny Mount, the diff nose will be lowered enough (by about 3/4") to interfere with the rear sway bar. How does this NOT happen to those of you that have used the GM Mount? Are you using a sway bar that is different from the stock location?

I'm planning on grinding down the GM mount, and possibly the differential bosses so that it will sit at more or less stock height, but if there is a better way please let me know.

I am currently running a bump stop on the top, but it still moves a bit and I like the idea of having the diff secured on both top and bottom-you know, like on a normal car.

[Zed Head]

Maybe some are leaving off the reinforcement plate that comes with the Energy Suspension mount? That would raise the diff nose up a small amount.