My wife's out of town this week, so I got zero play in the rear end.

 

OP.
Lounge reply.


Technical response.
The amount you are turning the DS that has you concerned is typical and not indicative of a backlash issue between the ring and pinion. Of course this is assuming the gear are properly set up.

The majority of "play" in any straight axle rearend is the sloppy fit between the axle inner end splines and where they insert into the side gears in the diff. This fit is a clearance fit by design and gradually gets sloppier as the miles go by. This is what you are feeing by turning the DS.

 

This. It's play in the axles, if your ring/pinion backlash was that out of wack I don't think you'd be able to drive it much farther then your driveway...

 

Thanks guys.
I had posted on "Drivetrain" and got no responses in 2 days ...

If my problem is in the axles, should I be able to verify it by doing the following:
- have the transmission in 1st gear so that the shaft is "locked"
- lift only one rear wheel off the ground
- see how much I can free-turn that wheel

If anyone knows, what would be normal amount of turn if my axle vs. side gears fit is fine?

By the way, the differential is brand new as well ... I didn't want to make the story too long.

 

A problem of excess curiosity usually isn't in the axles. If you did rotate a wheel like that, you'd find an amount of rotational movement in the wheel/axle too, which you'd find scary and we'd tell you was normal as well.

If the rear is quiet on the road at speed, then the gear pattern is likely set up correctly.

If your curiosity is still overflowing, get a stethoscope (harborfreight) and listen to the diff. while the car is running on jackstands.

Or, drop the cover and dump the break-in oil. Get some marking compound, wipe down several teeth of the ring gear and mark a few teeth before putting it through a forward rotation with the pinion. Take some high-res pictures of how the drive pattern looks and post them up. Otherwise, you're just burning electrons here.

Nice choice of differential, BTW.

 

Matthew, I am not sure what you mean by "curiosity" ... my curiosity about "the play" or is that how you call the sloppiness in the rear end.
Anyway, it is not that I am just wondering whether the play in the drive-shaft is normal. I am trying to figure out what is wrong/different with my car compared to before recent events. I was trying to avoid the long story, but I'll go ahead with it and try to make it not too long.

I got the car in 2006. Didn't notice the whine when I test-drove it, but learned right after that my rear-end is whining at 50-70mph (6th gear, enough speed, but low engine noise). It wasn't bad, but definitely noticeable. I read the forum and noticed that people were saying the "Richmond gears are tough but on the noisy side". I had a friend check the backlash and while we were doing so we realized that I have Richmond gears. Since then (for about 5 years now), I got used to the whine and since there was no change/increase I didn't worry about it.
Recently, since my tires were ready to be replaced, I decided to take the car to the drag-strip. I was just curious as to what the car can do as is (stock except for gear change (from 3.42 to 3.73 done by first owner). I made 10 ish runs with times form 13.23 to 13.8x. While coming around for another run I noticed some ticking as I was coasting and about to stop. Looked into it and figured that I shouldn't race it any more but that it was good enough to try to go home. The car made some growling noise related to wheel speed (enough to keep me on my toes) and I could feel ticking in the shifter at slow speeds with no gas.
I took it to a local shop (Mr Norms Garage) recommended by my neighbor. They took the rear end apart and said the my differential/carrier was worn and the side gears have slop in them so the diff needed to be changed. I questioned that quite a bit, but ended up saying yes as they seemed sure that was it. I also asked them if it made sense to change ring and pinion, especially if there is a good chance that would take care of the whine I had all along. The main mechanic said "if it were mine, I wouldn't. They are fine and I'll set them up right and probably make it less noisy. Although, these are always going to have some amount of noise, no matter how well you set them up". Once they changed the diff and I took the car, I realized that the car behaves exactly the same way it did before the repar - growling noise at any speed (the faster, the more noise) and ticking when coasting at very low speeds. I took the car back and they basically said "It must be ring/pinion .... we'll replace it without charging you for labor since we advised you not to change them last time". Of course, I wasn't happy about them having changed the diff (as it probably didn't need to be changed), but all I could do was accept their offer and have them change the ring/pinion. Once that was done, there was no growling/ticking any more. The whine is there again ... a little louder than before the track, but that wouldn't bother me much as I am somewhat used to it and it doesn't feel broken, just a little annoying. What DOES bother is me is the following:
Every time I push the clutch in, if there is still some throttle in (like you would when you are about to shift, normally) I can feel some sort of a click (like a sudden metal disengagement). MORE SO, when I let off the clutch (if I don't do it very carefully) it feels like the drive-train bounces back and forth. Also, almost every time I approach a stop light/sign by getting it out of gear, coasting and stopping, once I am putting it int the first gear I can hear/feel a thump from the rear of the car. All that lead me to take a look at how much "play" there is in the drive-shaft/rear-end because it just feels like there is more sloppiness then before. In all that, one could say that I may be just imagining it, but having driven this car for last 5 years I am sure there is something that's quite different than before and that is not right, so before I went to another shop and had them do/change whatever comes to their mind first, I thought I should ask you guys for some help and try to figure out what the culprit is - whether something in the rear end was not set up right (knowing that the diff, gears and all the bearings are new - it would most likely be a wrong setup), or do I need to take my attention to the transmission.

By the way, both times Mr Norm's garage did the repairs I asked for the old parts. The pinion had visible cracks in it, which means they made a bad call when they replaced the differential first time. It pisses me off, but I guess that's the price one pays for not doing things himself (which I would love to do, but have not means/space/tools nor right kind of friends to learn the tricks from).

Anyway, sorry for the long post - I should really watch those electrons I am burning ;-)

 

Have you replaced the u joints?

 

When I went under to check "the play" I was hoping to find that U-joint(s) were the problem. However, after taking a good look I found them to be nice and tight. Everything going into the rear-end is turning together with the drive-shaft, but then inside the rear-end there is amount of free-turn that reflects as 10-15 degrees on the shaft (1/4-3/8 on the outer diameter of the 3" shaft)

 

Right. Load/unload of the diff. and the center hub of the clutch disc are normal events and some noise will occur there even when they're perfect / normal / new.

The growling increasing with speed puts the issue somewhere between the output shaft and the differential. So, did the axle bearings get replaced? The rear 2 bearings in the T56 are seldom culprits of this nature.

This could be a lot of things outside the diff. from the trans mount, torque arm bushing, various items bolted to the diff, to rear suspension parts like loose swaybar end links, shock bolts etc. If you can duplicate the noise repeatedly with the car up on jackstands and a helper, you can probably tune into where the noise is coming from, either by sight of a loose end link for example or by sound by touching various things with a mech. stethoscope until you narrow it down.

Some of the load/unload characteristics could point to a clutch disc hub spring noise.

Something else abstract - is everything interior-related properly in place? A gap between the lower shifter boot and the floor could make a little problem louder. Even the jute behind the carpet missing, the carpet not tucked under a rear hatch area trim piece etc. could make the car less enjoyable which is important.

As for the rotation of the driveshaft, that's normal and characteristic of a hypoid gearset. That amount changes slightly depending on gear ratio and isn't a valid point of reference. Nor is rotating a tire while the other is on the ground and the trans. is in gear. Both are like a manual trans. on the bench with lateral play of the pilot end of the input - irrelevant. The pinion bearings are key and are responsible for keeping the gear pattern consistent.

It sounds like you may have another noisy rear diff. but one that'll give you similar amount of service as the last. And a noise or two external to the diff. that you can track down with some effort.

 

Thanks a lot for you response/help Metthew!

Understand, the amount of "normal" noise is what I'd say I had before the track night (with the exception of a little more whine at 50-70mph). That's something I could easily live with. What I am trying to figure out now is the "shaft bouncing feel when shifting" and the "thump after coasting and when putting in gear". Those two I believe come from the same source/problem.

What I called growling was nose that started on the track night. Its frequency was lower than gear teeth meshing. If sounded like something that happens once per turn of the driveshaft. The first repair round had the following parts on the invoice:
-Truetrac rear differential $399.95
-bearing kit $48.95
-3 Mobil 1 oil 75w/140 $21.99
-friction modifier $14.00

The growling continued and then they said the gears needed to be replaced, which included:
- ring and pinion set $207.95
- Shipping Expense 9.95
- pinion seal 10.71
- bearing cone 39.35
- installation kit $38.95

After looking at the old pinion it was clear that the growling noise came from it having two cracks (one on each side of one particular tooth)

So, growling is not there any more, I just have a little more whine (which sounds/feels like gear meshing noise) than before the track night.

I am having a friend come over this weekend to help me with what you are suggesting.

While I believe that all these things can contribute and cause unwanted noises, I doubt that my problem is one of those. It is hard to explain ... being in the car and/or driving it is the real deal.

In the meantime, I checked the driveshaft play on an 2000 S10 (190k miles on it) and on my neighbor's 2006 Silverado (~100,000). They both have considerably less play (half of or less then a half of Z28's) in the driveshaft.

 

Matthew, that is!