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Need some rear differential help

6.5K views 15 replies 8 participants last post by  papawpaul  
#1 ·
Hi All,
Looking for guidance with a rear differential problem with my 2005 Chevy Silverado 2500 HD truck. According to the RPO codes it has the G80 - axle positraction, limited slip and the GT5 - axle rear 4.10 ratio rear end. Approx 230,000 miles. A nasty grinding sound started coming from underneath the truck after I did some brake line work. Was hoping I'd left a piece of old brake line hanging over the driveshaft but no such luck. Was hard to tell where the sound was coming from, even with the wife driving and me hanging off the tailgate. So I raised the rear wheels off the ground and carefully checked things out and it was definitely the rear differential. Took the 14 bolt back plate off and didn't collect much used oil, maybe a quart. Also had about an inch of metal filings on the magnet (forgot to take a picture). Tried new diff. oil and gasket and backplate but no joy.

I haven't ever tore into a differential before, not sure I could. So was hoping maybe someone here could give me some advice as to what I could do. Don't want to sink a fortune into such an old truck, but it's been good to me. Thanks for your help.
 
#6 ·
Perhaps a near by wrecking yard would have a Posi 410 rear axle. If you haven't rebuilt a rear axle then I don't recommend you go that route. It takes some special tools and knowledge of how to properly set up a diff for good service life.
 
#7 ·
Thanks for the advice, pretty much what I had figured. It's one of those when do you cut your losses things. But had just installed new NiCop brake lines all around, and new rotors and pads on all 4. So maybe if I can find a rear axle for cheap....
 
#10 ·
The rear diff if properly serviced on these last many miles. if you install a new diff make sure you drive it very easy the first 500 miles.. then after 2K miles replace the gear oil with the cover drop.. the reason these do fail is because people do not drop cover/replace gear oil at the proper time/method.. the box requires cleaning... the gear oil after breakin of the 2K miles should be good for 40K miles then service it ..

on the cheap which is also a good method find a diff at a scrap yard . these are not hard for a shop to install not much labor. I would also replace the U joints at the axle rear connected to the diff...

make sure the breather hose is not damaged blocked or missing ..
 
#8 ·
Really pulling the carrier and pinion out is pretty easy. Also replacing the bearings is easy too, with the proper tools.

I'd pull the axles, carrier, and pinion and replace all the bearings, seals, and crush sleeve. Also id make sure to flush out the axle tubes and pumpkin very well so no metal shavings ruin your new bearings.

The hardest part is setting the backlash properly but it's actually not bad ounce you do it. Your current shims should pretty much get you there. Also preload on the pinion shouldn't be too tight.

If you decide to do it yourself, stick your new bearings in the freezer and the carrier somewhere hot for an hour or two and the bearings should almost fall on.

Worst case, pull it apart and flush everything really well and let a shop replace your carrier and pinion bearings.

Edit: bearings, seals, crush sleeve and fluid will cost you less than 100 bucks and your time. Also you'll get to learn somthing new.
 
#11 ·
With rear wheels off the ground, it is normal for the G80 posilock to clunk when one wheel spins and the pawl locks both wheels. That means the G80 works. Try applying some brakes with the wheels off the ground and in drive.
The grinding could be just bad bearings just like on my 2001 suburban with 230k miles.
 
#12 ·
Thanks to everyone for your good advice and your kindness to someone new to your forum. I don't have any experience with differential bearings but have changed out a few wheel bearing assemblies. With wheel bearings there would be a constant whine which would get worse when that side of the vehicle got more weight in a curve. With my current diff. problem the grinding sound was not constant, but would start when driving like every 20 seconds and last about 5 seconds. I'm guessing the bearings are bad and need replaced, just not sure if that is what's causing the intermittent grinding sound.
 
#14 ·
Did you miss the inch of fuzz on the magnetic drain plug, j cat?

Ted
 
#15 ·
I see that the other day on a dodge challenger had 10K miles on the new diff.. many on these do not drop the cover so the metal will be much more so the drain plug does get fouled faster..

before I would replace this I would do a complete inspection now where did the gear oil go???? probably the wheel bearing seals ...
so dropping the rotors and inspecting the compete deal esp. at this mileage is what I would do...