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Discussion Starter #1
I'm having problems with my diff in GTO again. It was replaced under warranty Dec 2007. Well now I'm having the same problems again with the clunking and howling. Changed the fluid, still the same thing. So I'm going to tackle this, to see whats up with it. Is there any service manuals that cover the specs of the diff, backlash, ect? The GM service manual covers very little about the diff. Also what special tools I need?
 

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I was going to check my new Helms manual, but sounds like you already got one (awesome, btw).:cheers

Just working from theory here, your clunk would be from excessive lash, and the howling would be from excessive pinion/ring gear tooth wear (which would cause lash over time). You are one of the lucky guys with a Maggie, so its entirely possible that your motor beat the snot out of your gears. :willy:

Good question, though. This will definitely take some investigating, and I'm sure this will help out more than a few people in the future.

Are you just going to do the gears, or are you planning on upgrading to like a TruTrac?
 

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Discussion Starter #4
No, I don't beat on my car I pretty much pu$#yfoot the thing because I'm still on the stock driveshaft. I used to give Dana big prase for their bulletproof diffs they was the TH400 of diffs. This diff seams to be so finiky and crappy its unbeleavable.

What I wanted to do was drop the cover and check the gear faces to see if they have any abnormal ware. If not then I would like to adjust the lash and press foward. If not would like to upgrade the gutts if the wife lets me.
 

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Yeah if you see any kind of cupping on the tooth surfaces, then they're toast. I wish I knew of a way to measure them in a non-arbitrary way with a dial calipers.

Perhaps my Machinery's Handbook will say something about excessive lash...
 

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Discussion Starter #6
I can't find data on this diff, no torque figures, backlash settings, how to adjust it, nothing. Have to get rid of the intermittin clunk and the whining at 45-50mph under load.
 

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rear end removal thread- LS1GTO.com Forums
swapping the gears-
LS1GTO.com Forums - 3.91 Gear Install...GHETTO Style


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Thank you Kurt from Diff Technics for the following:

IF the 3.46 ratio pinion that you “take” out of the diff has lets say a marking
of 0 and then the 3.91’s we sent you have a 2 marked on them this would mean
that the 3.91 pinion is .002” further into mesh with the ring gear than the 3.46
so you must remove .002” from the pinion location shim if it was the other way
round and the 3.91 pinion had a -2 (negative two) on it this would mean that the
pinion is .002” out of mesh with the ring gear center line, So hence you must
ADD .002” to the shim size and if you were luck enough to have 0 put it straight
in !!! I hope this helps you out on the location side of things !

Now as for the back lash .004” to .006” back lash is a must no more no less on
these ring and pinions !


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These are the stock (dana) specs for the LSD

1. Pinion Gear Bearing Pre-load 25-35 In Lbs (1.32-1.54 ft lbs), Add 8-12 In Lbs
If The Seal Is Installed. Light Machine Oil Only, No Gear Oil For Pre-load.

2. The Torque Spec On The Crush Sleeve Is In The 150-500 Ft Lb Range With 230ft
lbs The Usual Number Needed To Get You Close.

3. The Side Cap Carrier Bearing Pre-load Is 41-51 Ft Lbs With Final Adjustment
(load) Preferred Towards Pinion Gear. Light Machine Oil Only, No Gear Oil. Turn
the carrier approx 20 times or so, re-check the torque spec.

4. Backlash is 4-7 thousands with tooth pattern preferred over tightness. He
indicated a center to lower (towards small side of ring gear) contact preferred.
this should keep it quiet.

All Seals Should Be Greased With A High Quality Grease (i Prefer Moly on seals
and never used anything else) To Keep The Seals From Burning Out Prior To
Seating Up To The Metal Parts They Are Meant To Seal. Do Not Install Them Dry.

1) AXLE ASSY
2) BOOTS
3) INNER CV JOINT
4) OUTER CV JOINT
5) FLANGE
6) HOUSING
7) CARRIER COVER
8) AXLE SHAFTS
9) AXLE SEALS
10) DIFFERENTIAL CASE
11) SIDE BEARINGS
12) GEAR KIT
13) RING and PINION
14) REAR PINION BEARING
15) PINION SPACER
16) FRONT PINION BEARING
17) PINION SEAL
18) COMPANION FLANGE

 

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Discussion Starter #8
Thanks Ninjured, that helps me out a lot. Now it looks like I have to get some special tools, daaamn! Looks like this will be my first diff work, I can't go wrong with something thats allready jacked. Hopefully they're not worn to the point where I need to replace.
 

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Discussion Starter #10
It is some good info. I was getting a headache last night tring to find info about this diff. My google skills must suck because I was getting everything from handbags to insurance compaines.
 

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It is some good info. I was getting a headache last night tring to find info about this diff. My google skills must suck because I was getting everything from handbags to insurance compaines.
Hell you should have seen what came up when I Googled "pearl necklace" for my mom's birthday gift. :eek: They were homemade necklaces but I don't she would have liked them. :eek:
 

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Well, my Machinery's Handbook hashes out what is tolerable backlash for a given gear set, but there is no way of giving you a concrete number without first knowing the gear pitch and tooth angle.

A rough estimate, according to the book says that you should not be seeing more than a .010-.020" gap between teeth in a high speed application. Some lash is required to allow for lubrication, and supposedly you need slightly more as the operating speed of the given gear set increases.
 

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Are parts availble to repair the diff? I was under the impression that it was pretty much a replace only kinda part. I do know Rocksand Racing does rebuild and upgrade them, but I would be courious to see if they order parts from somewhere or fab everything themselves.
 

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2006 GTO Rear end

Does anyone know if the 2006 rear end is a limited slip or an open diff? My car spins one wheel and i was not sure if it suppose to or if the clutch / limited slip is no longer working.
 

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It is a limited slip. It uses cones as "clutches" and they can wear out. There is a spring kit that increases the cone pressure and the fluid can play a part too. You can try changing fluid. I would recommend Torco RGO 85-140 and Torco Type "F" friction modifier.

The "instructions" are 2 oz modifier for a standard rear end and 4 oz if it has an aftermarket Harrop cover. The purpose of modifier is to allow controlled slippage of the cones. I would only add a little over half the recommend amount and then take the car for a short drive to mix it. After a short "mix" drive in slow, tight circles to the left and the right. You may hear popping from the rear meaning the cones aren't slipping smoothly. If you do add a little more modifier and repeat. Do that until on those slow tight turns until it doesn't pop anymore. I wouldn't add more than the 2 oz.

As you can see I don't like the lubes with the modifier in them as you have no control over how much is there. You want just enough to make it not make that popping noise but not so much that the cones slip all the time. If you aren't completely worn out that may fix your problem for now. Make sure someone doesn't talk you into getting Type "G" which is what normal GM cars use but being an Australian Dana rear end it takes "F".
 

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Ok so my "clunking" "scrubbing noise is my driveshaft......I don't have access to a jack at the moment. .......but my mechanic told me I was missing two of the three bolts in the driveshaft (don't know how they poped out ) but my ? Is does anybody know what size they are
 

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Ok so my "clunking" "scrubbing noise is my driveshaft......I don't have access to a jack at the moment. .......but my mechanic told me I was missing two of the three bolts in the driveshaft (don't know how they poped out ) but my ? Is does anybody know what size they are
If it is the stock 2 piece driveshaft your clunking might be due to the worn gasket in the middle. Mine was completely gone. I just got a 1 piece and noticed much smoother accleration.
 
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