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04 Sierra sle 5.3 2wheel
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Discussion Starter · #1 ·
So when I back up fast and stop as I'm going forward it's like something is locking up. When I get going good it stop and rides smooth but when I let off the ecclorator it make a roring sound like a Jake brake.. when I speed back up it stops I was low on rear-end grease and topped it off with oil and limitd slip supplement. Any please help!
 

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When driving forward you contact a different side of the gear than coasting or reverse. my guess is something is bad in the rear end.
 

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So when I back up fast and stop as I'm going forward it's like something is locking up. When I get going good it stop and rides smooth but when I let off the ecclorator it make a roring sound like a Jake brake.. when I speed back up it stops I was low on rear-end grease and topped it off with oil and limitd slip supplement. Any please help!
Is your rear differential stock? If so, the limited slip additive is probably causing the problem, it's a no no in a G80. I'd pull the cover and start counting teeth, both the spider gears and ring and pinion!
 

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^^^^ good catch. The stock G80 is a locker, not a limited slip. Do not add any additives to the lube.
 

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Look at the glovebox service part label and see if it has the G80 code on it.
 

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04 Sierra sle 5.3 2wheel
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Discussion Starter · #9 ·
Seems like it don't do it going straight but when I turn either way it starts locking up.
 

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Yes, you have G80... a rear "locking" rear differential. Drain it and inspect everything. If it looks good (no metal shavings) put in fresh synthetic fluid. I think 75w90 is the correct weight. Do not use any additives.
 

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04 Sierra sle 5.3 2wheel
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Discussion Starter · #12 ·
Yes, you have G80... a rear "locking" rear differential. Drain it and inspect everything. If it looks good (no metal shavings) put in fresh synthetic fluid. I think 75w90 is the correct weight. Do not use any additives.
Thank you very much
 

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Look at the RPO sticker in your glove box.

GT4
Rear axle, 3.73 ratio
GU4
Rear axle, 3.08 ratio
GU5
Rear axle, 3.23 ratio
GU6
Rear axle, 3.42 ratio
 

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2004 Sierra 3500 6.0L, auto, extended cab, cab&chassis, upgraded to 4wd
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Just JB weld that bad boy back on... :)

Depending on how fast/cheap you need it repaired, you might get a used axle with the same ratio from a junkyard/used parts shop/someone parting out their truck, or get the diff in your truck rebuilt, either by yourself or a shop.
 
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