G80 Rear Differential
 

Hey guys. Is there a simple way to test a G80? I don't think mine is working properly since I have gotten it stuck a couple times and I would notice that it seems to be operating just like a normal differential (one wheel on each axle moving when in 4LO stuck in mud). If it is not working properly, is there a simple fix? I don't know if this is related but I know for a fact that the last time I had the rear differential flushed (at around 75,000 miles) they said the fluid was dark. Thanks

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G80 Test Procedure

If your fluid was changed with standard non-locking differential lube it will not work properly. Most posi-traction units I have dealt with only lock the wheels together if they are filled with the correct fluid that has some type of friction properties. That could be your only problem...just my .02

The G80 diff is not a posi-traction differential. It is an Eaton Gov-Loc unit. No friction modifiers are required. Just standard GL-5 equivalent or better 80w90 (or 75w90 synthetic) is all that is required.

I have a 00 Blazer 5 spd 2 wheel drive and it has a factory locking diff. What kind of diff lube can I use and what weight instead of going to the dealer? I went to the dealer and bought what they told me and changed it out when I first got it and it was expensive.

Um... Did you read what I wrote in the reply directly above yours?

I hope it didn't put you out.
thanks

ive often wondered if the G80 in my parts blazer is any good. it has 198,000 on it. maybe when my '97 rear end goes out (spiders and bearings bad, was ran low on oil before i got it) i can swap it in and find out. the bad thing is i have to change the front axle too. the "good" truck has 3.42's, the "parts" truck is 3.73, id rather have the lower ratio, but it means alot more work with the different ratios between vehicles. i may take apart the G80 this summer and go through it, its already out of the vehicle anyways, hope it wasnt ran low on oil like the "good" truck has been. is there a "overhaul" kit of sorts for the G80? ive not done much diff work, mainly just changed fluid, replaced axleshaft seals.

There are a lot of special tools and measuring that must be used/done to rebuild a G80 properly. There are places that say they do this, but I wouldn't put a lot of faith in rebuild G80's lasting too long. It really isn't something you want to spend your time trying to accomplish yourself. There are aftermarket diffs out there that will last longer and perform better than a G80.

As far as swapping goes, you'll want to swap everything over. I can't remember the specifics, but I believe that the 3.73+ carrier is a different series (spacing from centerline of pinion to ring gear mounting face) than the higher gears (lower numerically). If that is true, you cannot swap your gears to the G80 from the parts truck and have it work properly.

My advice would be to rebuild both the front and rear axles from the parts truck when you can and then swap them both into your truck when the opportunity presents itself.

3.23 and numerically higher gears got the 3 series carriers, so swapping gears wouldn't be an issue... but I agree it will be a whole lot easier to just swap the whole rear in.