Rear suspension advice requested

[MEZZZ]

To start, '77 280. Front end rebuilt last fall and just finished the rear last weekend. I installed, Illumina's, Eibach springs, ES poly bushings (all of them), S/S brake lines, shoes and wheel cylinders. I also have a new set of Konig 15's with Toyo 225/50/15 installed. I also installed one of Zonsdabrain (Dave) R/T style diff. mount. Everything (including gas tank) was removed, cleaned and painted.

The front end was completed last fall, I test drove about 5 miles with no issues. Rebuild included Illuminas, Eibachs, poly bushings, Moog ball joints, wheel bearings, ball and socket kit for tension rod, toyota 4x4 brake caliper upgrade with cross drilled rotors and S/S lines.

I dropped the car last weekend and eagerly got in it for a short test drive. I still need to get the car up on a ramp and re-tighten a few bolts to torque per the manual's instructions (weight on wheels, 2 people in car).

First, I heard alot of gear noise. I am wondering if that is the mustache bar poly bushings and am asking you guys your thoughts. I am thinking of using a 1/8" to 1/4" rubber insulator between the body and the bushing. Any thought?

The stock setup had rubber in between ( photos from Zsondabrain and used without prior consent )

Also, I had a terrible sound coming a couple times while deaccelarating, like a gatlin gun noise, chattering, hard to describe on here. I am going to put the car back up on stands and double check everything, torque, etc.

I found this diagram awhile ago but it seems to be missing F thru J being marked on it. I need to ensure that all the bolts and nuts are torqued to spec and cant find some of the settings in the manual. Thank you for any help you can provide.

Not sure why but when you click on the diagram it is coming up white on black and hard to read. If you click on it while open, it will open correctly.

Edited August 28, 2010 by MEZZZ

[BuDavid]

the poly bushings you have from ES are supposed to cover the edges of the mustache bar and therefore insulate the surface under the washers, but you must keep in mind that poly bushings are stiff and will transmit vibrations to the body, not 100% of them, but some will.

but for the gatlin gun noise, I'm looking forward to see what are your observations after you check again.

just look again at the things that you didn't replace, I mean the things you needed to move to access the replaceable stuff, maybe you forgot some of those.

have your halfshafts U-joints checked too. while you are under.

[MEZZZ]

I didnt replace the half shaft U-joints or the wheel bearings. I pulled on the wheels prior to the start of the project, 12-6 and 3-9 positions and they felt fine. I kick myself for not doing the rear bearings when I had it apart, just because of the "while I am at it" syndrome. The rear exhibited none of the symptoms before the rebuild so I have to assume it is something I did (or did not do).

I only drove it around the block and cant remember if the sound came when I applied the brakes or just when I let off the gas. I will attempt a short drive again and see exactly when it makes that chattering noise.

On the mustache bar mount, you are correct, the mounts do cover the top and bottom of the actual bar with the metal washer on top (and bottom). I was just wondering what effect it would have if I put a piece of rubber between the body and the top of the mount. With the current setup, the large metal washer is up against the body and in the stock form they had that wavy piece of rubber. I did fail to mention that I drained and re-filled the diff while out but doubt if that had much to do with it.

thanks for the reply

[BuDavid]

if I'm not mistaken, if you put the rubber, it will insulate more, but on the other hand it might stress the differential mount (if it is poly) and for the mean time, if you have rubber diff mount, and poly mustache bar bushing, maybe you are doing the opposite right now.. I don't remember seeing any of poly diff. mounts before.. again, I'm not sure of this point, and if there is anybody who can correct/confirm, that would be good, I think of it this way because the mustache bar bolts right into the differential so anymovenet in the differential will put load on all of mustache bar bushings and the diff mount.

for the rubber material, you can use tire pieces, they are made from good rubber, thin rubber will break so soon. my PO used that method, it worked, but look ugly like hell.:paranoid:

[Zs-ondabrain]

Hey MEZZZ, Those pics look pretty damn familiar .... You know that's a 260Z right? Not sure of any differences between the 77's and 74's but just so you know, those are 260Z pics. I don't honestly think there is rom for a rubber insert, and it won't likely reduce the noise by much, if any. The tube insert and urethan will be bolted up pretty good so the transfer is likely there for good.

Dave

Edited August 28, 2010 by Zs-ondabrain

[Zed Head]

I think that the nose of the diff tends to drop on deceleration using the engine compression. I have read reports elsewhere of the rear driveshaft flange rubbing on the rear sway bar. That might be worth a look, regarding the Gatling gun noise, if you are running just the RT style mount and have removed the stock one.

I have played around with the moustache bar stock mounts to get rid of "clunking" using stacks of rubber and metal washers and found that the tighter it gets the more gear noise you get. That is noise transmitted up through the body, the stock mounts are still isolating the sideways vibration. So rubber insulators might be worth a look but you will still have the vibration path sideways, with the hard urethane mounts, from the moustache bar through to the metal sleeve which contacts the car body (as ZODB said above). I'm interested in what you find, I have held off installing the urethane mounts due to the gear noise issue.

Edited August 28, 2010 by Zed Head

[Zs-ondabrain]

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.

another thing to do is shave the inner steel tube that is in the center of the mustache bar sides. This might, Might allow the compression of more Urethane than steel to steel.

Just thoughts, nothing tried and true.

Dave

[MEZZZ]

Good points, thanks for the advice. Dave, I ddnt think you would mind the pic grab, at least it shows I DO search before starting a new thread

Not sure of the difference between your 260 and my 280 if any, I really only used the photos to show the old stock rubber and the new poly mount. Mine looks dead on yours with the exception of the red bolt heads, its almost as clean looking now!

Could it be in the R/T type diff mount itself? I went with the E/S GM tranny mount method. Using that method, I could not use the stock lower mount or the stack of steel that were installed in later years. I believe the stack was added on later models (it almost looks like some type of counterweight constructed out of 4 or 5 1/8 inch plates) to help reduce vibration.

Is it possible by using the R/T mount, Ive actually added to the problem? Also, does anyone have torque seting on all nuts/bolts associated with the rear end? I cant seem to find them all, see 1st photo in post.

thanks guys

[MEZZZ]

Ok, please look at Daves pic, (the clearer one with red bolt heads) and mine that I snapped last week. Note the position of the moustache bar compared to mine. His is behind the mounts (silver) and mine is mounted in front of them. Is this a difference between a 260 and a 280 or am I screwed up somewhere?

I originally installed the mustache bar like Daves photo (it looked to be like that in the Haynes manual also) and my diff did not line up. I swapped it around and everything matched up fine. Am I missing something here? I started this project last fall, it all made sense to be back then but that was back then.

Edited August 29, 2010 by MEZZZ

[paul dinnell]

I had a gatlin gun noise when i backed up in my 1977 280z, and it turned out to be the drive shaft touching the rear sway bar. I have a stock rear mount.

[Zs-ondabrain]

See what ya get for stealing? but seriously, you're talking Potatoes and Potautoes. Your later 280Z with an R200 and my 74' 260Z with an R180.

My diff is shorter and has the mustache on the inside. yours is longer and sits on the outside of the hangers. In the pictures below, you'll see my R180 and almost perfectly aligned half shafts. (aligned with the stub axles, almost dead on 90 degrees)

Is your driveline touching or hitting the front diff crossmember? When you use the R/T with the GM poly mount, it lowers the diff a little in the front. It may have put your into the crossmember.

At this point, if you still have the stock diff mount? Go buy a bump stop, reinstall the stock diff mount, install the bump stop. This should minimize some vibration and help Sandwich the diff between rubber and urethane.

Just a suggestion.

Dave

[MEZZZ]

Dave, that makes me a feel a little better. When I went to put the diff back in, I had the bar located behind the hangars as in your photo, the manual showed it like that. When I went to put on the crossmember, no go. Backed it out ans reversed the moustache bar, reinstalled (with the stock lower mount), didnt fit. Backed it out again after reading up on it, discovered I couldnt use the stock mount with the GM mount I had. Took it off, reinstalled and everything lined right up.

Being the idiot that I am, cleaning up a couple weeks ago, I tossed the stock mount and the "counterweight" looking thing. After everything went back in, the diff felt locked down and I really didnt think I would have to do this a 4th time

I bought in on the R.T mount from you early, before the bump stop option was described and bought the G.M. mount.

I will get her back up on stands today and see if I see any evidence of it coming down onto the crossmember and if so, I will do the bump stop option and get a new lower mount. I REALLY dont look forward to redoing this job again

I jumped in Monday for my test drive for the first time since last October thinking this thing should handle like a go cart. At least it looks good sitting low in my garage

thanks!