I need some dimensions or pic moustache bar area

[madkaw]

I will have to drag out my r200 bar and compare it ( thickness) with the r180. Hell I don't even remember if I still have it now that I think about it.

I realize there are a lot of reasons for clunking and thuds and thunks, but I think I have experienced them all. I've had loose gland nut clunk and the loose diff nuts that clunked and of course the diff mount. This noise is different and like I said earlier it seem to come about when I did the STI swap.

Zed, I did have 4 large washers that are about 1/8" thick each. This really compressed the rubber . Now when I stick a pry bar in there it hardly moves.

I didn't get a chance to drive since I have to work. I also didn't do it right . I put both washers on the bottom, so I need to re do that which means dropping the M bar.

[Zed Head]

I think that if the rubber compressed you did it right. Worth a test drive. Not sure what you mean by did it wrong, unless you're talking about the slight change in diff angle. A test drive will tell you if the clunk is gone, even if you have a new misalignment noise.

[madkaw]

I should have put one washer on each end of the curl instead of putting both on the bottom. I would want the inner steel bushing to be centered right?

With both washers on the bottom the bushing won't be seated against one of the washers if I am thinking correctly.

It was easy to just add the washer on the bottom but the top will require dropping the M bar clear of the stud

[zKars]

How about this? Replace the stock nub washers (they are called 'Stoppers' in the fiche) with thick all-rubber washers. This replaces the stock nub washers compliance with more rubber, thicker than the nub washers so they compress when tighted down, and you have a chance of using different durometers of these washers in a effort to both increase stiffness and maybe affect sound transmission. No danger of metal washers coming in contact with the center sleeve.

Hey, get real fancy and make multi-layer washers with different density layers to reduce sound transmission (each density change creates another reflection interface). You knew we'd have to start re-engineering this and start using 2$ words, didn't you?

One source of really tough rubber washers of the right diameter and thickness might be the muffin tops (sliced off) of a set of poly replacement MBar bushings...

[madkaw]

The center steel bushing of the M bar rubber bushing is surrounded by a layer of rubber almost all the way to the ends. Don't see how the washer is going to come in contact with any metal.

[Zed Head]

After you do some experiments you'll see why someone took the time to mold a new bushing. Even if you get the up and down part tightened up, there's still the side to side. The only problem with the urethane bushing kits is that they made the sleeve too short, allowing the nuts and washers to compress the bushings too tightly, passing more noise from the diff. If I was installing a new kit, I might just get a piece of metal pipe and make my own sleeve, of an improved length.

It's a shame that once these things get in to production, mistakes and all, they never change. Most aftermarket parts are really just good starting points.

[madkaw]

I kind of found that out doing my control arm bushings(outer rear). You can't just slap those urethanes on and hope it's right.

I'm going to play around with this for a while. I like how quiet my running gear is now-except for the banging now and then. Once you have things tight under hard acceleration and gearing there is no noise or banging to speak of. It's the changing of the loading on the M bar that is noticable.Besides the fact that it took a lot of effort to install those stock bushings-

[zKars]

I have a report on my m-bar stock bushing replacement.

I found that the old stock bushing rubbers were in sad shape. Not just soft, but cracked and crazed like mad. Passenger side was considerably worse. I replaced them with stock ones, but did something similiar to what I alluded to above with my poly muffin top idea.

First, let me mention that the preceived softness of the rubber in the old and new bushings aren't that different. I tested this by putting the M-bar in the vise, then putting a large screwdriver through the metal tube in the eye of the bushing and pull/push to get deflection. The cracks and nasty-ness of the old bushings became very apparent. After replacement I did the same thing, and while it was somewhat stiffer, not that much really. I also tested the vertical deflection, which is where the changes were very much more apparent. With the old bushings, when I would jack up the rear end with a floor jack under the diff, the diff would rise a good inch before the car started to move.

Between the main bushing deflection, and the soft and not-so-much-there-anymore nubs on the stopper washers that weren't hardly doing anything to prevent vertical movement, the M-bar was free to move up and down WAY too much. When I squish the new stopper nubs with my thumb, they aren't all that much stiffer then a bunch of old used examples I have so I decided to try to do something to improve vertical constraint. Hopefully without increasing noise transmission.

I have several sets of poly M-bar bushings laying around, after doing several poly bushing jobs and convincing most folks to stay with stock bushings to keep the diff whine in check. I decided to use only the upper larger OD section of a pair to replace the stock stopper/nub washers. This required that you have to do two things. Remove the muffin top of the bushing and increase the ID of the hole in the bushing to 1" to fit over the center metal tube on the eye bushing. I used a thin cut off wheel (1/16") in my 4 1/2" grinder to remove the top of the bushing (worked schlick, clamped the lower part in the vise and slice away) and then a big 1" twist drill to drill out the center. (its about 3/4" to start with). I was surprised how well that worked.Gives off a neat spider web of melting poly strings as you do it too!

I used an old upper stopper (the hole is bigger on the upper stopper) above this poly muffin top, but removed the nubs, all but a thin layer of rubber that I left bonded to the metal washer. THen the muffin top, then the M-bar. The thickness of the poly muffin top closely matches the stock nubs and fills the space nicely with slight compression. I did not repeat the poly muffin on the bottom of the eye, thought I'd try just the top first. So the metal parts of the stack up are exactly like stock, so it tightens up like normal, only difference is the replacement of the nubs on the upper stopper with a donut (muffin, croissant, whatever) of poly.

Will mention I have the R/T mount in front with the poly snubber above like GrannyKnot.

Ok, enough yakking. Put it all back together, and went for a drive.

There were several immediate improvements.

1. Clunks are gone. Diff no longer contacts the LSD finned cover diff brace.

2. Diff whine/noise is actually reduced if anything. Introduction of 'some' poly back there did not increase noise transmission.

3. The drive line is 'tighter'. I used to have quite a bit of slope and chatter back there which I attributed to diff and C/V play, but its all gone. Apparently keeping the diff in place and the U-joints/CV's angles controlled makes for a smoother drive line experience. Imagine that.. Totally shocking news, eh?

Now I realize the diff wants to twist, so there is likely reason to have poly both above and below the M-Bar to really constrain it. Given what happened with noise transmission change (ie none) I don't think putting in a lower muffin would be an issue. And its so darn easy to do below the M-bar. I'll complete that and let you know the outcome.

Temper this with my comment above re: upper stoppers being NLA from Nissan Canada and Japan, maybe this is a way around this growing problem. Can the lower stoppers be far from extinction as well? At least you can drill out a lower stopper to make it work as an upper (only difference is the through hole, larger on top to fit the M-bar pin OD changes).

[madkaw]

Jim,

Thanks for the report. This is a r180?

My clunking still persists and it has been definetly worse since going all rubber.

I like your idea and wish I had some old urethane bushings to tear up like that.

Keep us updated, might be my next project!

[zKars]

This is with an Z31 Turbo R200 w/finned cover.

I will check the inventory and see how many poly bushings I have. I can slice and dice a couple and make them available. I also have way too many old nub-less or nub-poor stoppers to use as well.

[madkaw]

So LSD also .

[Zed Head]

Here's a picture of something I did just to see if it would have an effect. Big steel washer, and big rubber washer that fit the outer diameter of the bar but with a big hole in the middle, for up and down, and also smaller washers that fit just inside the inner diameter to reduce side to side. The rubber was just to avoid any buzzing or rattling. The picture is with the jack under the diff but you can see that the bottom scalloped washer still is compressed. I had more installed than shown at one time, enough to transmit diff noise to the cabin.

Ace Hardware washers, nothing fancy. It was a good experiment for my purpose.

Edit - might as well show my next experiment, to try and avoid the diff noise from the urethane bushings. I cut a boat trailer roller in half for the top bushing, and used the urethane on the bottom. Urethane kept the diff located side to side and the looser bushing on the top damped the up and down. Worked well, but looked ugly and started showing signs of age. Eventually went to all urethane but with an air gap to avoid noise transmission.

Edited June 27, 2014 by Zed Head