What goes bad first in a rear differential?

[The motor guy]

I'm at 247,000 on my 11.5aam rear end. This one has actually been maintained, so come rebuild time, do you always have to do a full rebuild or can you just put a couple new bearings in it and save a bunch of money? It's not giving me any issues. Makes me wonder how much longer I have before it gives up the ghost? This is my 2007.5 dodge cummins 6.7

 

[ripcord]

My cousin in law put a million miles on a 2 valve Cummins driving a rural mail delivery route. He never mentioned working on the rear end, just a transmission.

 

[Oillover]

The fluid.

 

[Speedbird001]

I would guess a seal > leakage > low fluid > higher temps > donski

Couple times I've had diff problems it was some kind of harsh sounding clunking, especially when turning. I was smart enough to take most of them in straight away for a relatively low cost repair. (With the VW I was 20 and broke... rode it out another 6 months and it was then unrepairable and required a full rebuild of a used unit)

 

[PontiacHO]

At this point, drive it until you see a leak and-or hear noise. Likely won’t be any more expensive for that repair as disassemble now for bearings-(pinion, carrier, & axle) and seals-(pinion and axle).

 

[4WD]

The fluid.

That’s what happened on my 2002 Ram 1500 - viscosity break down and equal opportunity parts failure … (bought a used rear axle) …

 

[pcoxe]

The pinion seal went leaking first on my 84 Camaro. Several years later the outer pinion bearing seized.

 

[Astro14]

Rebuild if it needs it - and I would think seal failure followed by fluid loss would cause the damage requiring a rebuild.

Otherwise - do the seals if they start to leak - but I have not seen a solid axle rear end wear out from mileage or use alone.

 

[vwmaniaman]

My 07 Ram Hemi broke a spider gear tooth off. My driveway was icy and the road was not. spinning tire suddenly grabbed dry pavement a tooth broke off. Fixed it myself with a gear set from RA. That was about 2 years ago. Tow our small 5th wheel camper with it.

 

[SC Maintenance]

They can last a really long time if there maintained and don't tow or haul a lot. My Xterra has 414K miles. Its treated mostly pretty easy.

If your towing or pulling often you can actually wear out the ring and pinion. But usually a bearing fails first - one of many.

Pinion bearings can on some models be replaced fairly easy if you don't have to take the entire assembly apart. If you do - then you might as well replace everything - the gears and all the bearings, and inspect the other stuff like the spiders and carrier.

 

[Snagglefoot]

I'm at 247,000 on my 11.5aam rear end. This one has actually been maintained, so come rebuild time, do you always have to do a full rebuild or can you just put a couple new bearings in it and save a bunch of money? It's not giving me any issues. Makes me wonder how much longer I have before it gives up the ghost? This is my 2007.5 dodge cummins 6.7

A lot of the cost is the labour to pull the gear set to access the bearings, then set it up again after the bearings are replaced. You’d have to price the gear set to see if it’s just smarter to just do the whole thing. Generally the gear set is less than $750.

 

[wwillson]

I'm at 247,000 on my 11.5aam rear end. This one has actually been maintained, so come rebuild time, do you always have to do a full rebuild or can you just put a couple new bearings in it and save a bunch of money? It's not giving me any issues. Makes me wonder how much longer I have before it gives up the ghost? This is my 2007.5 dodge cummins 6.7

We have several of these American Axle differentials. When they are maintained, as in the fluid changed on schedule, they will last almost forever. We pull heavy trailers and have never had any problems with any of the AA differentials. The trucks are almost never unhooked from the trailers so almost all the miles are hard working miles.

I would bet you'll never have to do anything to the differential.

 

[Jetronic]

Rebuild if it needs it - and I would think seal failure followed by fluid loss would cause the damage requiring a rebuild.

Otherwise - do the seals if they start to leak - but I have not seen a solid axle rear end wear out from mileage or use alone.

I've seen one grenade, but the truck was used for roadside maintenance (greenery) so likely was running in 1st gear mostly and starting/stopping a lot. I didn't find a history for diff oil changes, but the carnage was still oily.

 

[50yr Street Mech]

The diff fluid 1st, then the bearings & seals will follow from bad diff fluid. So, CHANGE YOU'RE DIFF OIL / FLUID

 

[oil pan 4]

I'm at 247,000 on my 11.5aam rear end. This one has actually been maintained, so come rebuild time, do you always have to do a full rebuild or can you just put a couple new bearings in it and save a bunch of money? It's not giving me any issues. Makes me wonder how much longer I have before it gives up the ghost? This is my 2007.5 dodge cummins 6.7

The pinion seal usually goes first some time around 10 years or more. Usually just change that and nothing else.
Eventually the axle seals go some time around 20+ years. That may prompt a wider rebuild. If the ring and pinion gear wear are within limits usually just seals and bearings unless you want your gear ratio changed.

The number 1 killer of rear diffs appears to be oil contamination usually water followed by lack of oil when it slowly leaks out.