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help, new rear end diff, bad noise part II (long)

495 Views 3 Replies 1 Participant Last post by  camachinist, 
G
Hi guys,

So here is an update, and more info:

I took the car by the mechanic, and he agreed it was a very strange noise . . .

Background:
Car has new auburn diff, new ring and pinion (3.55), new springs (mid-eye), new bearings and retainers, new oil seals, and the rest was from before (poly bushings).
Car set up for street/strip
.006" backlash
.014" pinion pre load
load side positive
The car makes a *loud* vibration noise (not a whine, it's between a whir and a growl, but loud) on deceleration (engine braking, neutrel coasting nearly silences the vibration).

From the descriptions in the shop manual, I don't have bearing whine or clicking or grinding noises, as it doesn't happen under acceleration, and no chage when switching left and right.

I'm not sure of the brand of the pinion and gear, cost was $170

Things I've done myself:
I tried rotating the driveshaft so that it is 180 from the position I believe I removed it from relative to the pinion (mechanic painted the diff and covered up the scratches i made). I jacked the car and made sure that everything ran smoothly without load, which it did. The noise was muuch less when jacked, mainly because the car's inertia was not working against the engine in a coast. I also jacked the axle up a few inches so that the pinion angle wasn't as much, but no change.

What I noticed:
On accleration, the pinion gets pulled upwards relative to the carrier, *and* the axle housing rotates slightly when the car is jacked up. The whir happens on "coast" when the pinion drops back to the default position. I can see the driveshaft shift in position a little matching the movement of the carrier. THe noise does appear to be coming from the carrier only.

The mechanic told me to bring it in and we'll pull it and look at it.

So anyway, if you recognize what this is, I'd appreciate hearing it, the mechanic seemed puzzled by the noise and couldn't offer a suggestion off-hand.

So, wish me luck, hope the gears are not fried already.

Thanks,
Chris
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C

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10,537 Posts
#2 ·
The tooth pattern on the back of the ring gear teeth likely will indicate some or all of the problem.

It's possible that you got a bad set of gears....it happens..

If you have access to a digital camera, photograph the gear set and any other evidence you find and post it..

Any funny noises when decelerating into a turn?
 
G

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Discussion Starter · #3 ·
ok, well, I guess I'll be able to see mon-Wed when we pull it at the mechanic's . . . my camera broke /forums/images/icons/frown.gif

Haven't noticed any funny noises, I think I would have if there were any. . .

Is it possible that the axle housing isn't seated correctly? I did switch from regular springs to 4-1/4 mid-eye and did final clamping on the axle u-bolts with springs uncompressed . . I need to read the procedure for clues, will do that tomorrow.

Thanks,
Chris
 
C

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10,537 Posts
#4 ·
From what you said in your first post, IIUC, the items you changed in the rear were the differential carrier and gears. Externally, you installed new springs.

If the assembly didn't make noise or vibration before, I would think that checking the parts replaced would be a good start. I would think, if something is amiss in the springs, their mounts, or attachments to the rear end housing, that you would have evidence (noise) of this under nearly all operating conditions, as the springs and housing are moving and under stress during all periods of road motion. Do you have any traction devices attached? It is possible the housing and springs are amplifying an existing noise/vibration but I don't think they're the cause...

Update us when you have further information!
 
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