Hi guys,

I picked up an 2006 G80 posi unit with about 60k miles with bearing s still attached that was pulled from a members truck. Wanting to install it in my open 2009 4.3 4x4 rear for some added snowstorm traction, no burnouts here.

Can I simply open her up, remove the open unit remove ring gear and install it on the the g80 and slap her back together. They are 3.73 gears and obviously the pinion gear wont be touched during this process.

Is it generally hit or generally miss, are the open vs G80 tolerances close enough that I don't need to worry?

Also what lube, and is friction modifier needed like my old 5.0 needed?

Thx

 

You can read this thread. https://www.performancetrucks.net/fo...Install+How-To

I would check backlash and pattern of the original set before taking it apart and try to get the same readings with the G80 when you stick it back together. As far as friction modifiers go, I had been running Amsoil Severe Gear oil and never had to add the modifier. From what I was told by an older GM Tech try it and if it makes noise come back in and get the modifier. Ran 20K miles like that and it would still engage properly and never chattered at all.

 

It take a 75W90 GL5 rated synthetic..no additive..

What GM says about a friction modifer in the G80..

***Important: Installing any friction modifier causes the clutch pack in the locking differential to slip and miss engagement. A fluid flush can often remove debris that is a contributor to clutch chatter. Adding friction modifier additive can cause a loss of locking differential functionality***

What the manufacturer of the G80 says...

"From Mr. Ralph Holmquist of Eaton, the maker of the locking differential:
"The maintenance schedule for the rear axle was developed by American Axle &
Manufacturing and GM truck based on multiple tests. The Eaton locker does
not require additional maintenance nor does it add heat to the lube. The
lube will darken due to the carbon wear on the clutch surfaces, much the
same as a disc brake pad & rotor. This does not damage axle components such
as seals or bearings. However, a new axle can produce excessive
temperatures (plus 350 degrees F) due to the ring & pinion breaking in that
will break the lube additives down. Avoid high loads, trailer towing and
high speed extended driving during the initial break in of the vehicle.
After the break in period axle temps will level at a much lower figure.
Lube changes are a good idea because the additives are replenished and
contaminates such as casting sand are eliminated. The axle is filled at the
factory with a synthetic 75w90 GL5 rating made by Texaco under part # 2276.
The GM service # is 12378261. This is the only lube we have done extensive
testing with to insure locker compatibility. The only negative to using one
of these other lubes is an increased potential for clutch chatter. This
really doesn't hurt anything and can be corrected by changing the lube. I
noticed in the latest GM owners manual the term "or equivalent" when
referring to the lube specification. Look for a GL5 rating on the bottle to
make sure the ring & pinion, seals & bearings are protected. Limited slip
additive is not needed."The following information outlines the type of
rear axle lubrication utilized in GM Truck axles.
I. Fluid Type
II. The 1500, 2500 and 3500 GMT 800 Trucks utilize SAE 75W-90 Synthetic Axle Lubricant. The GM part number is 12378261 and the specification is 9986115.

 

Thanks a lot for the lube info. I will stick with those specs.

Anybody else want to chime in on my chances of a successful direct swap?

 

If it matters I did the straight swap and it has held up for over 10000kms with no whine or anything.

 

I did the swap on mine about 30k miles ago. Checked the pattern before removing. Swapped the carrier out and rechecked the pattern. I reused the old shims and just had to swap sides when I reinstalled the new assembly to get the pattern to match back up. No problems here.