2003 GMC Sierra rear diff posi

Badass69 · May 16, 2016

G80's last forever for people that could drive with an open rear and get where they are going mostly anyway... weak junk since inception back in the 1973 model trucks... real modern too.

Trutracs are good in a front diff... useless in a rear in my opinion. But they drive like an open rear so people love them lol. Lockers like a Detroit are great... and if you think that a Detroit will put you in the ditch on icy roads please do all us other drivers a favor and go cut up your driver's license lol.

Inherently however Internet forums will always favor a trutrac so whatever the op chooses will do him well in all likelihood.

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Nanotech Environmental · May 16, 2016

I've had a truetrac in the rear of my truck for quite sometime now. Works great in everything I've put it thru. It does what its supposed to.

JerryCanada · May 16, 2016

A welded diff can put you in the ditch fast in the wrong situation. I would check the RPO codes and make sure the G80 is what you have. The TruTrac is a very viable replacement, despite not being a locker. It's a decent design that's pretty tough.

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I work out of town but will be home on Thursday to check the code in the truck. I have the build sheet from GM and it is on there. I drove all last winter in snow with a 2WD '95 Toyota Tacoma with a welded diff and no issues there.

Also on another note. Was talking to a mechanic buddy of mine and told me to add some sort of additive in the diff that might not have been put in when (and if) the diff oil has been changed. This might fix it too.

intheburbs · May 16, 2016

Also on another note. Was talking to a mechanic buddy of mine and told me to add some sort of additive in the diff that might not have been put in when (and if) the diff oil has been changed. This might fix it too.

The G80 requires no additives. A typical positraction rear with clutches needs a "friction modifier" additive to keep the clutch plates from chattering. Since the G80 does not have clutches that need to slip when turning, nothing additional is needed.

Badass69 · May 16, 2016

I work out of town but will be home on Thursday to check the code in the truck. I have the build sheet from GM and it is on there. I drove all last winter in snow with a 2WD '95 Toyota Tacoma with a welded diff and no issues there.

Also on another note. Was talking to a mechanic buddy of mine and told me to add some sort of additive in the diff that might not have been put in when (and if) the diff oil has been changed. This might fix it too.

As the guy above said no additive. If it hasn't grenaded by ripping the teeth off the lock plate.. or the shaft on the engagement pawl there is a chance someone put enough friction modifier in it that it won't work properly... or at all. Wouldn't hurt to pull the cover and take a look at it to see what is a going on. I always love the fear of welded diffs and lockers lol... it's hilarious what people say.

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SouthernSilveradoGuy85 · May 16, 2016

My '98 had the G80 and ya I abused the hell out of it and had 2 diffs basically explode because I would do burnouts and everything. If you power brake it and do it long enough while it's doing the 1 wheel peel then the other side will lock and then let the brake go so you leave 2 marks. Sometimes I would back up out of a spot and then do it and it would already be locked.

The G80 did save me one really good time. I was in a mudhole deep enough to where the water was just above the bumpers and water was coming into the cab. The '98 was just leveled by the way. I was able to get it out on my own after rocking it back and forth a few times. Probably took about 5 minutes. If it didn't have the G80 I'm not sure it would have got out without someone pulling me out. Also at least in the '98, it did seem to want to lock if it rained or was raining hard enough and it would sip while turning.

My '14 also has the G80, but it seems like they've upgraded it or something because it didn't do like my '98 did sometimes. The G80 might not be the best, but it does what it's supposed to do, especially the newer ones from what I can tell.

Badass69 · May 16, 2016

It's the same design pos your 98 had.. what's changed is manipulation of the rear brakes that affects how it engages...

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SouthernSilveradoGuy85 · May 17, 2016

It's the same design pos your 98 had.. what's changed is manipulation of the rear brakes that affects how it engages...

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Well my '98 of course didn't have TC or Stabilitrak like the '14 so I guess that's why it doesn't feel the need to lock on just a wet road. I guess I was assuming it was something to do with maybe a new design or upgrade. Either way at least the one in my '14 is beefier since it's a 9.5" 14 bolt and my '98 was just 10 bolt (can't remember the size). I don't tend to do the stupid stuff in the '14 that I did in my '98 so the rear axle on this one should last the life of the truck as long as I change the gear oil when I need too.