Strange Noise

[sac001]

OK, about 2,000 miles ago, I rebuilt the Rear differential and Trailing Arms. While I was at it, I had the U-Joints on the half shafts replaced, replaced the brakes, e-brakes etc. Essentially I had everything from the driveshaft back rebuilt, all new hardware, poly bushings etc.

Now, when I start out, I'm getting a strange noise from what appears to be the Left rear wheel. It doesn't have the heavy Clunk of a U-joint problem, sounds like maybe a spring or a stuck or sticking emergency brake, but it happens whenever I change direction, regardless of if I used the e-brake or not.

I've pulled both rear wheels, and can't find anything obvious, no rubbing scraing hitting or anything of the sort. I've checked the differential fluid, and re-lubed the grease fittings on the half shaft u-joints.

It almost sounds like something is moving in relationship to the change in direction of the car. Is it possible that if one of the bushings isn't seated correctly that this could happen?

Anyone have any ideas or help, I'm pulling my hair out on this one and don't have much left to pull!

Steve

 

[Bullitt]

If the parking brake was adjusted out too far, I think you would've had this problem from the get-go and in a straight line, too. It could be however that maybe a spring broke or wasn't seated properly. Check the p.b. hardware by pulling off the rotor. I'd even back the star adjuster off a few clicks to see if that's the problem. Also check the mounts of the sway bar, if you have one mounted. It could be loose on that side. I hope it's as simple as that.

--Bullitt

 

[sac001]

Yeah, after writing that all out, I started thinking parking brake also. I know I recently adjusted it up a bit, but can't remember if I did that before or after the noise.

I'll check it out tonight and see if that is the culprit.

I did check the sway bar when I was underneath and everything looked and felt tight.

Thanks for the feedback, it's always good to hear from those that have been there. At least it makes me think I'm on the right track.

Steve

 

[vmrod]

noise culprit

I recently rebuilt my 77. (from the rear of the transmission to the wheels). Once complete, I rolled it forward then backwards and heard a slight 'clunk'. After some detective work, I found out that my driveshaft yoke (near the transmission) was hitting the emerg.-brake pulley.
It turned out that my transmission mount was shot and allowing the transmission to wiggle around a bit. A new mount cost $5! Done!
-Vic

 

[sac001]

vmrod, thanks for the tip. I checked last night and like I thought, all hard connections appear good. No rubbing, scraping or other marks detected.

I adjusted the Left Rear e-brake a little, but probably not enough. The noise is still there. I only hear it when I change directions, if I stop and restart in the same direction, generally there is no noise. It sounds like a spring sticking then releasing.

I'll put the rotor off tonight and check out the works. Do you think this could be cable related, either underneath or at the wheel? Any advice is appreciated.

Steve

 

[chevyaddict]

Me too!!

It is a very distressing noise isn't it? I, as well, just completely rebuild the rear-end unit in the 81. Everything is back together and now I get this noise, especially if I make left hand turns. I can't seem to find anything visible. The rear-end was rebuilt through a very reputable shop so I am certain they did everything right. Otherwise, the car is as smooth as a whistle. My noise is definitely sounding more like something hitting as the tire is going around (or a driveshaft going around) then anything. I will check to see if my tranny mount is shot. If I find anything that hasn't already been mentioned here I will let you know!!

By the way, thanks to those that explained to me to get the longer bolts to lower the rearend down with that new spring. Car looks great now! Just installed them yesterday!!:Twist

 

[sac001]

Chevyaddict, if it sounds like something hitting as the wheel goes around, check the mickey mouse clip that holds the e-brake cable to the T-Arm. If it is installed with the "ears" pointing out (away from the T-Arm) it tends to hit any wheel weights you may have on the inside of the wheel. I had this problem not too long ago, but that was an easy fix, just turn the clip so the "ears" point towards the front or back of the car.

As far as my noise, I pulled the rear wheel & rotor off & checked the e-brake and all looks well, except the brake shoes seem to move a significant amount, perhaps an inch or so either way off center at the bottom of where they meet at the star adjuster. The pins that hold the brake shoes to the backing plate look OK, but this amount of movement seems excessive. Does anyone know of a way to tighten this up? I think what is happening is that the e-brake shoes are shifting and that is what is giving me the noise. I didn't see any damage and think I may just have to live with it if I can't tighten it up.

Thanks for your help everyone!

Steve

 

[Yoda]

Another source of noise when changing directions comes from brake pads . Take the back wheels off ( uh.. be sure to jack the car up first ) then take a large screw driver and wedge it between the lugs and move the wheel back and forth. Sometimes the disc brake pads are a tad small and will shift back and forth causing a very iritating click as the brake pads shift because of direction change.

Everything else mentioned in this thread is a possibility, I chased a similar noise for about 2 years.. found mine to be the cross differential shaft in the rear end to be worn allowing the end gears to chatter.

And we all know to use the GM Lubricant Additive GM 1052258 in our :booty right?

Good Luck finding this "Click click" noise.

 

[sac001]

Thanks for the TIp Rare81. I'll add that tot he list of things to check, but I'm pretty sure it's in the e-brake assembly.

The noise I'm hearing sounds like a spring popping, or the brake cable sticking then releasing, or something like that. I guess I'll lube the e-brake cables while I'm at it.

Steve

 

[78SilvAnniv]

Hey Bud,

I have a bottle in front of me (NOT a frontal lobotomy!) of GM Limited Slip Axle Lubricant Additive, #1052358. Do I have the correct bottle (should my bottle say 'posi' on it?), or do you have a number switched?
Heidi

 

[sac001]

Rare,

When I did the rear, I did use the Posi additive, not the GM stuff but an equivalent from NAPA. The noise I hear has nothing to do with turning or speed, it only occurs when I first change direction (foward or reverse) and I think what is happening is the lower portion of the e-brake assembly is shifting on the backing plate.

When I pulled it apart, there were some marks on the backing plate where the shoes ride and the assembly easily moves about an inch forward or backward if I push it on the bottom.

The retaining springs are installed through the shoes, and the pins to hold them are engaged, they just don't appear to be very tight, and allow the shoes to shift. I can't think of how I could make them tighter, to hold the shoes more securely, or if I should even bother. I can't even see where the pins come through on the back side, or how I could replace them with shorter pins to put more pressure on the springs, thereby holding the shoes more securely.

Steve

 

[Yoda]

Re: Hey Bud,

I have a bottle in front of me (NOT a frontal lobotomy!) of GM Limited Slip Axle Lubricant Additive, #1052358. Do I have the correct bottle (should my bottle say 'posi' on it?), or do you have a number switched?
Heidi

Yep oops should be #1052358 nice catch Silver

BudD

 

[Bullitt]

What could've happened is that when the p.b. hardware was replaced, the retaining pins were universal ones. If you bought a Corvette specific kit, then it should not be a problem. For general information though, let me go into detail.

Generic or universal kits have longer retaining pins. This doesn't seem to be a problem, as the springs and cups they are used with accomodate the extra length. However, the wheel studs from the back will rub against the pin. Turn the wheel spindle and you'll hear an audible click as it revolves and makes contact with the pin. It's easy to replace one pin, but the other is "trapped" because of the rotor flange. What needs to be done, some will say is to disassemble the whole assembly. Don't cry yet. Remove the trailing arm nuts (accessed with the removal of the p.b. mecahnism) and pull on the rotor flange. Yes, you'll probably bend it, but it can be easily bent back into place. This is easier if the trailing arm is off the car, but can be done, if there is not a removal option. Needle nose pliers will come in handy to remove and reinstall a correct retaining pin.

I learned this the hard way myself. The upside? Umm... let me think for a minute.....

--Bullitt

 

[sac001]

Bullitt, thanks for the info, but I'm not sure I understand. I had the T-Arms done by a shop, and they re-did the e-brake assembly as well, so I have no experience taking it apart (or putting it together).

It does look very much like a typical drum brake assembly, except you can't get at it because of the rotor flange. Am I correct in that you think the retaining pins might be hitting the back of the wheel studs? The reason the sound would go away is then that the pins would have shifted in one direction or the other, right?

If this is the case, I should see some wear on the end of the retaining pins, correct?

As far as replacing the retaining pins, I didn't comprehend how I can do that. From what I can see, there is no way to pull the pins from behind the retaining plate, so how would I get them out?

I think what I really need to do is stick my head under there, with the car on the ground and have my wife go back & forth a bit. (I'll do this with witnesses so she doesn't run me over accidentally on purpose), and see if I can tell what is going on under there.

Steve

 

[Bullitt]

This is just another possibility that I mentioned. What could be happening is that when you turn, the side deflection may just be enough to make the pin hit the back of the wheel studs. Since it only happens on a turn, this may not be the problem at all. It's a failry easy check, though.

What you can do, is disconnect the half-shaft and remove the rotor. Then rotate the spindle by hand and listen for the clicking. As the studs turn, they should make contact with the retaining pin, if this is your problem.

Since it's just like a regular drum brake set-up, the p.b. assembly is not difficult to remove at all. What you're referring to as the rotor flange is the spindle flange (this part carries the studs). It looks tough to get in there, but with the p.b. springs removed (lower and upper), you can move the assembly around to access the retaining cups and springs. I have a small Craftsman 5-piece plier set that was essential in removal. Sears #45671, about $25-30. The bent nose plier is the most helpful in pushing the retainer cup down to ease pin removal with needle nose, which are also in the small plier set.

Once the spring is compressed and the cup removed, one pin can be removed from the trailing arm. I'll have to check on it tomorrow to see which side (closer to the front of the car or rear), but the other pin gets stuck between the trailing arm and the rotor flange. Gentle hands and patience is all it takes to get it out, if it's too long.

Ask whomever did the reassembly, where they got the rebuild kit from or if they just reused some bits from the original. I went down to the local parts store when doing mine and found out that no one makes a small hardware kit specifically for Corvettes other than the ones advertised in catalogs. Like I said before, if it's a universal/generic kit, chances are the pins are just too long.

Rotor Flange: plate mounted behind rotor, stamped steel and originally gold anodized. A protective plate.

--Bullitt

 

[sac001]

Thanks for all the advice Bullitt. I'm heading out there now to tear it apart one more time. At least now I've got some pretty good clues to check out!

I'll let you know how I made out.

Steve

 

[sac001]

OK, here's what I've got.

Stuck my head underneath while the wife moved the car back and forth, didn't see anything moving or jumping around.

Jacked it up, rotated the wheel back and forth, no noise. Jacked up the left side to approximate "weight on wheels" situation. moved the wheel back and forth, no noise. Removed the caliper and rotor to inspect the p-brake assy, and could not find any interference between the p-brake retaining pins and the back of the wheel studs.

In other words, I can't find anything to point to this noise. The noise only occurs on initial acceleration in one direction or another, straight line or turning. No increase or decrease in the noise when turning as opposed to straight line. It does not sound like the clicking you get when you have a bad CV joint on a front wheel drive car. It does sound like a stuck spring popping free. Usually I get two or three "pings" then it goes away.

After numerous detailed inspections underneath, I can't find anything that appears to be wearing from movement that might lead me to the problem. (Everything underneath is new, and there is no scuffing of the paint or anything to indicate something is wrong.)

At this point, I'm stumped. Any suggestions are welcome.

Thanks,
Steve

 

[77-4speed]

Have you tried the posi additive yet? Could be a *slight* gear shudder. If nothing else seems amiss, posi additive is a cheap possible solution.

Russ

 

[sac001]

Yes, I used the posi-additive when I first re-installed the differential. Actually I'm going to bring it to a local shop for an oil change anyway, so I'm going to ask him to drain the differential, and re-fill it with the GM additive. I used the NAPA equivalent when I did it, and maybe that's part of the problem.

Thanks,
Steve

 

[77-4speed]

Don't forget that it might take a little more than the "standard" amount of posi additive. I've read a number of times where guys added the normal amount of additive only to hear gear chatter. They simply kept adding it a little at a time and the chatter kept getting less and less, until it finally went away.

Russ