Wierd rattling noise coming from rear: diagnosis?

[jeromio]

So I have the poor man's rear toe adjuster, and I was able to get my rear suspension pretty close to aligned. I drove the car around - streets, highway, etc. - and it was noticeably better. Then I took it to an alignment shop. The right contol arm is so hosed (badly bored pin hole) that the guy couldn't get it aligned - the adjuster is maxed out and there's still half degree of toe. So then I drive the car home - neighborhood roads, no speed involved at all - 25mph. Car sat for 2 weeks. Then I decided to drive it to work one day. At 35mph, I notice a funky noise. On the freeway, the noise gets way worse. It's like a rattling noise - maybe a combination of 2 different mechanical noises. It happens both on power and coasting. I pulled over, quick look, noticed a slightly soft tire. Drove to a station and checked and filled all tires. But that didn't help. Drove the car home very gingerly.

 

Some info that may help: I have 280ZX CVs with 240 stubs (new bearings) and home-made seals. Struts are sectioned and w/ GC coilovers. I also have rear discs. While I was making the poorman adjuster, I changed the fluid in the diff (4.11 R200).

 

So I jacked up the car a few weekends ago. I thought perhaps the alignment guy just didn't tighten all the bolts on the adjuster since there are 6 in total. But they were all tight. I checked ebrake cables, brake hoses, brake lines, fuel lines. CV boots are fine, Ujoints in drive shaft are fine. Everything looks fine - no obstructions, nothing unusual. I jacked up one side - noise seems to come from pass. side - by the end of the control arm so I could spin the wheel to verify interference. Nothing, no interference.

 

So, I still have this toe problem and I thougth maybe the extra bind in the bushings due to the extreme adjustment might be a problem. So I stretched the poorman adjuster to something very close to stock length and and cut the rear leg of the pass. side control arm, flanged it, clamped it, welded it back. It's shortened by 5/16", which is as much as I could squeeze it. This effectively put back to zero toe. Then I lined everything back up and tightened it. I can definitely get it aligned perfectly now.

 

BUT I STILL HAVE THIS %$@!* NOISE! I cannot figure this out. I drove it about 1/4 mile at 35mph and it sounds terrible.

 

And of course multiple things changed at once - although I don't really suspect the fluid change, since I did not hear the noise on my initial test drive - I drove it on the highway then too. The noise was only present after I got the car back from the alignment shop.

 

Now, I do still need to get it aligned, and the guy at that shop seemed pretty cool - since he could not align it (due to the rear arm being basically f'd up), he did not charge me. And he was happy to talk about possible solutions with me. So I think I will take it back to that same shop, and try and broach the subject of this noise, and how it only appeared after I got it back from him.

 

But do any of you have any other ideas? Possible things to check? I can't drive my car and it's making me sick.

[Doug71zt]

Is your outer CV joint bottoming out due to shortening the LCA and adjusting the bushings? That would be my first guess. Second guess would be the spider gear cross-shaft in the diff. If it starts to slid out of the carrier, it can make some weird noises as it hits the end of the pinion, case, etc.

 

Let us know what you find.

 

Doug

[2126]

You mentioned you have new stub axle bearings. Are the stub axle retaining nuts properly torqued (200+ ft/lbs..see torque specs) and did you use the recommended procedure to determine that you have the correct rotating resistance on the stub axles after torquing. Just a thought. But to determine a specific noise would be next to impossible, based on what you have provided....there's just to many variables. So, you know the drill....it's the old process of elimination...check one item at a time and move on to the next, unless the alignment guy left someting loose. Good luck there jeromio!

[2126]

Is your outer CV joint bottoming out due to shortening the LCA and adjusting the bushings? That would be my first guess. Second guess would be the spider gear cross-shaft in the diff. If it starts to slid out of the carrier' date=' it can make some weird noises as it hits the end of the pinion, case, etc.

 

Let us know what you find.

 

Doug[/quote']

 

Doug, good suggestions!

[Guest Aaron]

I'll be the one to post the non tech answer. I had a funny rattling in my truck that was driving me nuts. Got the truck on my dad's lift, went to beating on stuff with my hand and found the rattle. It was a rock that flew up and got on top of a something against the frame.

[jeromio]

Is your outer CV joint bottoming out due to shortening the LCA and adjusting the bushings? That would be my first guess. Second guess would be the spider gear cross-shaft in the diff. If it starts to slid out of the carrier, it can make some weird noises as it hits the end of the pinion, case, etc.

I can check this - I can crank the adjustment over to one side. This should stretch that CV.

 

I did think of CV bottoming. And the outer boot is really squished, but then I remembered it's always been like that. The small hole part of the boot is not clamped to the beveled "rest" part of the shaft for some reason - it's pushed over by about 3/4".

You mentioned you have new stub axle bearings

Yeah, but I did that work about 4 years ago. (Not dissing on your suggestion, just clearing up the info)

It was a rock that flew up and got on top of a something against the frame.

That's interesting. I can't think of places where stuff could gather, but I'll check next time I'm under the car. It is kinda hard to see the whole upper part of the control arm.

 

You know what's gonna happen: I'm gonna end up tearing apart the whole rear suspension. There was a slight chance I might make it to SEZ this year - that chance just evaporated completely.....

[mark]

Are you running the delrin and Aluminum control arm bushings?

[jeromio]

Are you running the delrin and Aluminum control arm bushings?

Nope I have this:

 

http://forums.hybridz.org/showthread.php?t=89111

[CruxGNZ]

For what it's worth, I had a rock fall into the rear control arm and drove me fricken nuts, because I couldn't see it. Took a while to find out it was a rock making all that noise. I'm thinking maybe the alignment shop guy dropped a nut/bolt and it fell into the control arm. Just another possibility.

 

!M!

[DCZ]

I have also had a rock bouncing around in the rear control arm. Another mystery noise can come from the gland nut at the top of the strut if it comes loose.

 

Jeremy - if you need a volunteer to ride around in the back and listen - give me a shout. If this sounds like a desperate attempt to get a ride in your car, it is! I also have a spare rear control arm you can have for cheep.

 

Damian

[jeromio]

Well, I guess Aaron and the rest of you must've been right. I found a loose thing-a-ma-bob piece of random metal in the back. Didn't seem like it could explain the noise. I might've also gotten rid of something in the control arm as I was blowing and brushing th esurfaces of both of them. Hard to say. But I drove around and the noise is gone. It's one of those annoying "Problem fixed itself" kind of situations. I basically just got frustrated at not really finding anything definitive and took the car for a drive. Couldn't reproduce the noise. And I tried. Wierd.

 

With all this I did come to a crystalline realization that my car is a piece of crap though. When I did all my mods to this car, I didn't do the Paraska style anal going over of everything in craftsman like detail. I basically just did a continuing series of tightwad, low budget, not much free-time available mods, one after the other. In looking for this noise, I inspected the whole car. You know that "Ugh, I should've done this or that" feeling you get when you're working on something unrelated? I kept getting that feeling over and over and over and over again.

 

My brake hardlines are random. Wiring is a mess. Got plenty of goober welds here and there. Interior is a mess. Exterior is full of dents, old bondo, rust, peeling paint. It all just looks so half-assed. The car runs and drives and all. But this whole mysterious noise thing has made me realize that I just need to go over the whole car and button up the thousands of little details and go back over all of my "quick fixes".

 

It's rather daunting. Don't get me wrong, I'm generally happy with the car and the structural, macro-level stuff I've done. It's just that alot of that is obscured by all the junkiness.

 

Anyway, thanks for all the ideas.

[CruxGNZ]

My brake hardlines are random. Wiring is a mess. Got plenty of goober welds here and there. Interior is a mess. Exterior is full of dents, old bondo, rust, peeling paint. It all just looks so half-assed. The car runs and drives and all. But this whole mysterious noise thing has made me realize that I just need to go over the whole car and button up the thousands of little details and go back over all of my "quick fixes".

95% of us have that! We all see it, we all think it, but as far as I know, you're the only one that has voiced it. As soon as you get settled, you will spend a good weekend and go through the car and make everything the way it should be and walk away with one hell of a grin.

 

!M!

[buZy]

Hey jeromio I think your zcar is cool. Keep going!