Noticed a loud clicking from the rear end upon setting out to return from a FLA conference. It only did it when coasting and quit as the car got below 20 or 25 mph. Took it to a shop and they found a broken spider gear bushing. They replaced the bushing but the noise was still there and they could find nothing else wrong. All gears looked good and the oil was clean. Rather than stay over the weekend I took the chance and made it home (SC-about 400 miles) with no problems except the noise when the load was taken off the engine.

It's a stock LG4 with a 700 R4 3.08 open. The frequency of the noise varies with speed and seems to be at driveshaft speed. It was observed in all gears except 1st. The shop duplicated the noise with brake drums off. There is no noise when the driveshaft is out. There is no vibration associated with the noise. The pitch of the noise will vary as the engine takes up the load of the car, like at the bottom of a slight grade. There is no noise or vibration when the engine is loaded or at cruise.

Any ideas?

 

Just taking a shot in the dark but a U-joint maybe?

would you be able to get a sound clip?

 

u-joints looked good but I'm going to swap driveshafts with my camaro tomorrow to rule that out.

 

Swapped drive shaft and no change. Could the shop have installed the wrong (or wrong size) spider gear bushings?

 

Spider gears don't have "bushings", at least not that you can change. They weren't "broken", and they didn't change them.

You can however buy new ones, as part of a "gear set", that comes with both spider gears and both side gears. But I'm betting they didn't do that either.

Spider gears are stationary inside the carrier when the car is travelling in a straight line. They only spin in the carrier when the car is going around a corner.

Forget about the spider gears. They aren't the cause of your noise.

Sounds to me like somebody has already taken advantage of you. Occasionally that sort of thing fixes a car, by lightening it; the excess load that is removed, is centered directly on the owner's wallet. That's what happened to you.

You have either a bad ring & pinion, or bad pinion bearings. If the noise is coming from the rear at all which I seriously doubt.

If either of those 2 cases is true, don't waste another dime on it. You have a crap rear end; one of the worst ratios, the small axles, 2-series carrier, drum brakes I'm betting. If anything about it needs repair, go get a better one, and throw that one in the trash.

On the other hand, if putting the transmission in a different gear fixes the noise, then the noise isn't coming from the rear anyway. It's coming from the transmission. You don't even have to be a "shop" to figure that out, only a slightly logical person.

Sorry to see you got ripped off. It sucks that there's people in the world that will do somebody that way.

 

The spider gears do have "bushings", the little concave silver colored "washer" that sits between the outside of the small gears and the carrier. I've pulled them apart myself when working on rearends. One of these was broken as the large part of it was attached to the magnet on the cover when the rear end was opened by the shop. Perhaps they have a different name?

The shop ordered a gear kit that included new spider gears, etc. and new bushings but only installed the bushings on my old gears. He couldn't get in the bushings alone before next week but only charged me the cost of the bushings (about $20). He'll throw the bushings into the kit when they arrive and return it.

I agree with you that the spider gears probably aren't causing the noise as it does not vary as the car corners.

But my guess is that something caused the "bushing" to break and/or a piece of it did damage elsewhere.

With the transmission in first gear, the car slows so quickly that I really can't tell if the chattering is there.

I'm not afraid to swap rear ends (installed a posi rear end in my camaro this time last year) but that's an all-day job and I wanted to narrow my list some first.

 

Those gears that the axles plug into aren't the spider gears. Those are the side gears. And that silver cup thing is not a bushing, that's a thrust washer. So yeah, a little terminology confusion there.

The spider gears are the ones that ride on the cross shaft, and the bushing for them, is pressed into the bore of the gear. The side gears don't have a bushing at all since they are held in place by the axles and the spherical shape of the thrust washer surface.

So maybe they did at least do something then, after all.

In any case, if shifting the trans changes it, it isn't the rear. So I don't believe it would make much sense to tear into the rear any more, until you can be sure it's really there, otherwise you might just be wasting your time and money.

 

The broken bushing (I think it's more of a bearing) was for one of the spider gears. They fit in a depression on the outside of the gear and ride between it and the carrier. The cross shaft goes through the gear and the bushing.

Keep in mind I was stranded in FL and hung around the shop all day watching them work.

They took the entire assembly apart and replaced both bushings. The old ones were shiny silver and the new ones were a dull grey metallic. They pulled the pinion and we inspected all bearings and gears.

I'm concerned that the replacement bushings may not have been the correct part/size. The noise did change from a louder, clicking noise to a dull chattering after the new bushings were installed.

I haven't ruled out the tranny either (parking pawl was a suggestion) although not detecting it when coasting in first isn't surefire as it doesn't really coast in first as the gear is so low.

Don't think I won't swap rear ends from the camaro to the trans am to get to the bottom of this. Just give me a sunny day in the 60's with nothing else I have to do.

 

Wanted to close this one out in case anyone cares. Issue turned out to be a chipped tooth on the coast side of one of the pinion teeth. Some of the metal from the broken bushing probably got caught in there while in reverse.

 

Glad you got it identified!!!

It's amazing sometimes what can be spotted by actually LOOKING AT something. Seems like that should have been caught the first time around. Any idea how a chipped tooth "escaped" being noticed?

And of course, it's STILL not a bushing that broke; it's a THRUST WASHER. The bushing is inside the bore of the spider gear, is made out of copper or bronze or some such, and has a surface that looks like a golf ball.

 

Yes, "thrust washer" fits the purpose of this piece perfectly. Thanks for defining the term.

Yes, it should also have been caught during the first inspection. I even inspected the gears myself and ran my fingers along all the teeth, of course I only felt the drive side of the gears. Then I got home, back on the computer, and on Randy's Ring and Pinion Site found the answer within 10 minutes. Swapped the rear end for the one in my camaro (and upgraded the camaro to a 3.27 nine bolt), pulled the cover and saw the prob right away once I knew what to look for.

On the positive side, if we had found the problem while I was in FLA I would have spent much more money on a new ring and pinion to make it home than the $250 I got the 9 bolt for (and upgraded the camaro to rear discs as well-iron calipers, I know, but it's a start).