GM TECHS Please or someone tell me about my rear end!

prorida

prorida

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Aug 3, 2007
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I've been trying to figure out how to make my truck posi-trac again. After adding over-sized tires and some power adders, i no longer have posi-trac. So I'd like to fix this problem.

I've asked this question before, with no definitive answer. I made a call to the local dealer, and i was told that I have a LSD Eaton with a 373 ratio, and a 11 1/2" ring gear. in my rear end. i was told that i could either buy new clutch packs or shims. Ok well sounds good i need to call eaton to get advice to decide whether to replace clutch packs or shim. and what shim to recommend.

A call to Eaton later, i was told that they don't make anything for a 11 1/2" ring gear, and that wouldn't matter anyway because they don't sell replacement parts. i would have to buy a whole assembly.

Eaton told me that my truck has an "American Axle" TracRite? WTF

WHAT IS GOIN ON! PLEASE HELP PLEASE
 
05_LLY

05_LLY

Out-A-Time
Aug 7, 2006
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Yes the Axles are american axles and your gm dealer should be able to get you any parts you need for them. I know a few guys who have installed the tru track (or what ever its called) that the dodge's use, its supposed to be a bit tougher?
 
McRat

McRat

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Aug 2, 2006
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It's a speed sensitive LOCKING rear axle. It has no bias (both tires spin opposite) when up on a lift.

You feel brave?

Here's how you test.

Jack rear wheels off ground. Use wood if possible in case truck jumps.
Have somebody sit in driver's seat, start engine, put in DRIVE and idle.
Put you foot on the SIDE of one tire to stop it. The other tire will be spinning.
WARNING - DANGEROUS: Have driver slowly increase speed to 8mph. By the time he hits 5mph, the tire under your foot will lock and start spinning. You cannot stop it.
 
McRat

McRat

Diesel Hotrodder
Aug 2, 2006
11,249
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www.mcratracing.com
There are several types of axles on the market:

  • Open Differential - the "normal" axle. Tires spin independently and share load only when both have traction. If one has no traction, it spins and the other one with traction does not, it just sits there, and so do you. Because this sucks in the dirt or snow, various schemes were developed so this doesn't happen.
  • Spools - No differential, both wheels turn same speed always. Think welded together. Off-road only.
  • DetroitLocker Locking Differentials - The unloaded tire must always spin faster or equal to the unloaded one. Locks up in corners if you have throttle applied. Not for street unless you are a masochist.
  • Speed Sensitive Lockers - Ours. G80 Eaton will lock if speed difference is more than 5mph. It unlocks when road speed gets to 20MPH. All other times, it's an "open" differential.
  • On Demand Lockers - Air powered or electric powered, you flip a switch and it turns an open differential into a spool.
  • Limited Slip Differentials - These use a clutch pack or cone to balance the load when one tire wants to spin. The best kind of differential for most cars and trucks. Like anything with a clutch, these wear out, and heavy use will kill them.
  • Torsen-Style High Bias Differentials - These are the coolest of the litter, and my personal favorite. These are gear-biased differentials that act just like open differentials with no load, and like a LSD as you apply power to it. Best choice for roadracing. No wear parts, and very strong.
 
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LBZrcks

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Jun 2, 2007
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Also it is not really posi, it's limited slip. How do you know it is not working? just curious. It will not lock if you are already driving not sure what mph. but at lower speeds or burn outs it should lock
 
L

LBZrcks

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Jun 2, 2007
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SoCal
McRat said:
There are several types of axles on the market:

Open Differential - the "normal" axle. Tires spin independently and share load only when both have traction. If one has no traction, it spins and the other one with traction does not, it just sits there, and so do you. Because this sucks in the dirt or snow, various schemes were developed so this doesn't happen.

Spools - No differential, both wheels turn same speed always. Think welded together. Off-road only.

DetroitLocker Locking Differentials - The unloaded tire must always spin faster or equal to the unloaded one. Locks up in corners if you have throttle applied. Not for street unless you are a masochist.

Speed Sensitive Lockers - Ours. G80 Eaton will lock if speed difference is more than 5mph. It unlocks when road speed gets to 20MPH. All other times, it's an "open" differential.
Click to expand...

Beat me to it:)
 
serpa4

serpa4

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Feb 5, 2007
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SOoooo
If I'm slipping, I need to slow down to below 20 mph and it will catch/engage?
Any 4x4 action needs to be below 20 mph? Like crossing a dry river bed and its getting soft, I'd instinctively give it some more gas, but should low to below 20?
If I drop the hammer and burn out from a stop, two tire patches.
If I drop the go pedal and burn out from a stop and keep going past 20 mph the diff will open and my two patches will change to 1?
If I give it the juice while already going over 20, say 25 mph, I'll only leave one tire patch?
Is the 20 mph limit the diff's fault or something GM had eaton build into the G80?

Good info guys!
 
prorida

prorida

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Aug 3, 2007
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Thanks guys and gals

WOW, i posted the same Q on the diesel place and i got one answer, and it was pertaining to the wrong rear end :jerkit:

thank you all so much for your positive no nonsense responses, in all reality i just wanted to fix what i have in there. no add-ons or different setup's. my truck is what they call a "mall-crusher" i'm not really off road with it (at least no more than north idaho will allow) just do a little bit of towing. Also i can't get the full benefit of chris "The Neens" tunes, if i can't get the truck to hook up.

I figure my "G80" is shot, solely on the fact that i no longer leave a two tire patch. that and when i rolled into it hard at 40mph, the effect usually lead to me correcting the steering wheel. lol

1 I'm guessing my "speed sensitive locker" is an assembly that i remove and rebuild? The dealer hard part#'s for clutch packs and shims, is that not meant for the "G80" or is the g80 built on the same theory as a normal Eaton LSD?

2 Is it pointless to rebuild the g80? will it not hold up long as compared to aftermarket equivalent?

3 kat and mcrat, what do you powerfreaks do?

4 All i'm really asking is what is the most efficiant and cost effective way to fix my little problem?
 
McRat

McRat

Diesel Hotrodder
Aug 2, 2006
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www.mcratracing.com
Burnouts are brutal on a G80. Just because it doesn't leave two black stains don't mean it's bad.

Try to test it a different way. Ice or oil or wet grass, one tire on, one tire off, and give it just a little throttle. Maybe with a couple of 2x4's in front of the front tires?
 
prorida

prorida

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Aug 3, 2007
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McRat said:
Burnouts are brutal on a G80. Just because it doesn't leave two black stains don't mean it's bad.

Try to test it a different way. Ice or oil or wet grass, one tire on, one tire off, and give it just a little throttle. Maybe with a couple of 2x4's in front of the front tires?
Click to expand...

Mcrat, i'm lucky in the way that i got neens to help me with my efilive needs and my room-mate is an ASE tech at a reputable shop, so we the lifts and tools we need to diagnose the problem.

i just figured that if it does not burn both, there's my problem. are you saying that if it passes the tests that you have given me, that it is fine. and may just need adjustment? cause i sure would like to go back to getting loose:rofl:
 
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