[quicksilver97ta]

Twice now.
I decided to put a fresh set of 4.11 gears in my Moser 12 bolt thats in the T/A as they were getting more noisy since the whole thing was new in 2001. I bought some Motive gears from Summitt (MGR-G888411) and had a highly recomended shop do the work. He followed the recomended break-in procedure while the car was in the air and I did the recomeded word of mouth short trip easy driving for about 200 miles. Then one day I finally got on it from a 5-10 MPH roll untill I shifted to 3rd (6 spd) and then let up after a second or two. On decel there was bad gear whine of two different pitches winding down all the way till I stopped. Hardly noticable on drive, very loud on coast.

So I bought another set of the same gears and worked a deal with the installer to use his shop and I did most of the work and checked all the install specs. The only thing I didn't have was a pinion depth tool but I even aquired the proper inch-pound wrench to check the preload on the pinion where the mechanic just went by feel the first time. This time we also replaced the larger pinion bearing since it is r & r'd in the process, it looked fine but just wanted to eliminate any question. We did move the pinion .002 as the pattern indicated it. We ended up with a TEXTBOOK pattern and set the backlash dead center within specs. Again all the breakin proceedures where followed.

These gears were at least if not quieter than when I recieved the whole thing new from Moser with just the slightest whine at highway speed, I was very happy with this set up especially since I did most of the work and checked all the specs myself.

Then I got on it and the same *%@^!!! thing happened again!
What is the deal? Are these gears soft? I find it very hard to beleive it has anything to do with the set up or the break in.
__________________

[Ron H]

What is the backlash?
I had problems very similar to yours. I found the splines on my axles and also in the locker were wearing and eventually I could actually turn my tire 3" without the pinion moving. This made for a whole lotta noise worsening over time. Now the gears I have are worn also and make some noise. They are US/strange gear and they also are getting louder with each trip to the track.

[quicksilver97ta]

Backlash is between 9 and 11, spec is 8 to 12.

[gearbanger]

I set my 12 bolt up personally with Motive 3.73s. They are dead quiet and have been for about 2000 miles now. I have run it a few times on the strip and it is pushing 550+ hp. Never ran it on slicks though. I am doubting the gears are soft. Could it be bad bearings or could there be remains of a rear gear breakage floating around in the housing and getting back to the gears or bearings and causing problems?

[quicksilver97ta]

Thanks for the replys. Nothing ever broke and there has never been any debris found. The bearings look great, they should with low miles. We just decided to replace the big pinion bearing thinking maybe it got tweaked somehow durring r & r.

Gearbanger did you get the "Factory" or the "Performance" gear set? They offer both and also an "Ax" set.
ALSO, how did you break them in before you nailed it??

[quicksilver97ta]

Also, when this happened with the first set Motive gears I tore it completely down and reinstalled with a new crush sleeve all within specs hoping to salvage the gears but it was still as noisy as before tear down. I did run it after that and the noise did not get any worse but I decided to buy new gears and start over, hence the second paragraph of my first post.

[Ron H]

Is this just street use or are you running at a track or with slicks?

[quicksilver97ta]

Both. The first time this happened I was on the street w/ street radials. The second time I was at the track w/ et streets but that was the first time I nailed it with that set. I blew the tires off though with only a 1.9 60' so they didn't get smacked that hard. It seems to make no difference as the results were the same noise.
And why on coast?? I don't get it.

[lust4speed]

It would be interesting to remove the rear cover and look at the current pattern and recheck the backlash. If I had to venture only one wild guess, I would go with the pinion nut backing off and allowing the pinion to move back slightly causing the noise on decelleration. Sometimes a pinion spacer or even the bearing or bearing race will hang up and you can have the proper preload until it moves and settles a little further in place. I've had this happen a few times so now I'll give the pinion gear a fair wack with a mallet to see if the preload changes prior to dropping in the carrier.

[Ron H]

Mine was really noisy on coast because the axle splines were worn. Now I have noisy gears but are quiet when I let off the gas. ou should jack the car up and turn a tire, watch to see how much play before the pinion moves. Could be the same problem I had.

[azmotorhead]

Noisy on coast is result of Pinion loosening.
Take it back to the shop and verify torque of Pinion nut.
Did they use the same nut to do final assy as the one they used when crushing the sleeve? Pinion nuts are a 1 time use. Sure you can stake them, but why when any good master install kit gives you 2 in the kit

[azmotorhead]

Now I have noisy gears but are quiet when I let off the gas.

this is probably because your pinion is set too deep. or backlash is too great

[Geoff]

Some of the gear manufacturers make a 'street' gear set & a 'race' gear set. The street gears are harder for long life, & the race gears are softer to absorb shock loads better. Don't know if Motive makes both types or only one type. Yukon seem to have a good name for quiet running.

[quicksilver97ta]

Phil, thats what I thought about the pinion. When I tore down the 1st job the mechanic did on his own I measured the backlash and it was wide, maybe .001 out of spec. He also had ten .010 shims on the left side of the carrier (which I swapped out for a .100 when I put it back together). Then I measured the pinion preload and it was 36 in/lb so it was tight, too tight, so I doubt it moved.

I will tear it down and measure again. This time I put it together and used my stuff to measure so it will be a true before and after comparison. I did reuse the nut this time since the extra nut I had that came with the gears would not work with the big 1350 yoke (you can't get a socket on it) but I did use red locktight on it.

Geoff, yeah I wonder about the different gear types. This mechanic likes Richmonds FWIW. I always heard they were noisy but he swears by them so I might go that route.

Thanks for the replys.

[azmotorhead]

Before doing the teardown get some of the marking compound and check the pattern before teardown.
That'll help determine what was going on in there.
Also the lastest gears I've recieved from Randy's R&P for the 8.2 Chevy rears were Mfg by AAM they are the suppliers to GM and many other corps.
Never had a problem with them. Only gears I dont like setting up are the Motives. Many have complained of noisy Richmond sets

[Billy177]

the only thing I can think of is maby your housing is defective somehow and the angle where pinion and the ring gear mesh just slightly off. On a side note I put a set of rihmond 3.90's in my car 3 weeks ago and they make no noise.

[quicksilver97ta]

Originally Posted by azmotorhead

Before doing the teardown get some of the marking compound and check the pattern before teardown.
That'll help determine what was going on in there.
Also the lastest gears I've recieved from Randy's R&P for the 8.2 Chevy rears were Mfg by AAM they are the suppliers to GM and many other corps.
Never had a problem with them. Only gears I dont like setting up are the Motives. Many have complained of noisy Richmond sets

Yeah I plan to check the pattern too, it will definitely be off if something moved.

Why don't you like Motive? What do you think about US gear? Thats what Moser put in it.

And Ron, I didn't notice anything on the axels splines, they are Moser axels. The whole thing is overkill but I had to step up from the 7.5 stocker before I broke it. It ran a 12.34 at 114 mph with a 1.9 60' and me granny shifting.

[matrix]

I bought a set of Yukon gears from Randys. Opened the box and found they were actually Richmond in a Yukon box. Took them to the "best" shop in town to have them installed. The mechanic took them out, saw they were Richmond and said "Just wanna let you know up front these are probably gonna make some noise". Sure enough about a 1000 miles in they started to make noise on coast. These are 3.42 gears in a 12 bolt, power coming from a mild 400 and a TKO in a 70 GTO.