What is the best option; rebuild or replace rear diff?

[Kernal]

I've had a howling or roaring that is directly related to road speed under normal load (normal acceleration or cruise) in my stock/locked 1996 FZJ- 80. The noise goes away once I take my foot off the accelerator or when coasting no matter the road speed. It started about 8000 miles ago and maybe has gotten slightly louder during that time. Went to a driveline specialist today and after driving the vehicle he said it was the rear differential (the front driveshaft is out and the CDL is locked). Haven't gotten the estimate for parts yet but his labor to remove/replace and rebuild the differential including pulling the rear axle shafts would be around $500, not bad. I asked him if it might just be the front or outer pinion bearing; he said it is more likely the inner/rear pinion bearing from his experience; said it takes more of the load?? From the Mud combined experience what might be the likely cause of the noise; pinion bearings(which one?), carrier bearings, ring/pinion??

 

[JO MAOMA]

Haven't gotten the estimate for parts yet but his labor to remove/replace and rebuild the differential including pulling the rear axle shafts would be around $500, not bad.

master rebuild kit is $200 if you need a new r&p another $230. regearing a
third around here is in the neighborhood of $350 drive in, $200 carry in so
$500 sounds a bit high...

From the Mud combined experience what might be the likely cause of the noise; pinion bearings(which one?), carrier bearings, ring/pinion??

takes about an hour to pull it and see whats up and then you save at least a
$100 bucks on the cost of a rebuild...

 

[Tools R Us]

... pinion bearings(which one?), ...

Doesn't matter, if one is bad, I would replace both pinion bearings. This is the most common failure I have seen. In all cases that I have done, the other bearings, gears, were good. If you have the proper tools, it's a pretty easy job. Need the pinion bearings, crush sleeve, flange seal and rtv to seal the diff, etc, back in.

 

[Kernal]

JoMaoma: Thanks. The mechanic said $450 and I figured with taxes etc $500, he charges $65 per hour so he's figuring seven hours work to pull the axle shafts and 3rd member, rebuild the diff and put it all back together.

Tools: I was thinking maybe buying some time if it was just the front/outer pinion bearing, wouldn't have to pull the 3rd. What special tools are needed? Started looking for low mileage used 3rds if I have to go that route.

 

[warpdriv]

Have you tried putting the front DS and pulling the rear to see if it clears up? Did the mechanic inspect the u-joints? It is a rarity that 3rd goes out.

 

[Kernal]

I haven't pulled the rear driveshaft yet and the mechanic did not inspect the vehicle, just drove it.

 

[Akella]

I have almost the same issue on mine 95 locked. Mine have been roaring for past 20K 160K now. it is only gets noticeable after 10-15 highway driving on a highway on a speed above 45-50. First i though it was my wheel bearing but after changing all of them it got better but did not disappeared. Now i am thinking either transfer case or rear diff. I heard that heavier oils can quiter the diffs. Can some body confirm that?

 

[Akella]

If you have the proper tools, it's a pretty easy job. Need the pinion bearings, crush sleeve, flange seal and rtv to seal the diff, etc, back in.

I am relatively new to mechanics and haven't done anything extremely complicated like diffs or headgasket. Now it may sound weird but how complicated to change bearings in diff compare to birf job? i mean in s

 

[spike6901]

JoMaoma: Thanks. The mechanic said $450 and I figured with taxes etc $500, he charges $65 per hour so he's figuring seven hours work to pull the axle shafts and 3rd member, rebuild the diff and put it all back together.

Tools: I was thinking maybe buying some time if it was just the front/outer pinion bearing, wouldn't have to pull the 3rd. What special tools are needed? Started looking for low mileage used 3rds if I have to go that route.

That is cheap...but I am assuming that is only labor? I had mine rebuilt a few months ago and changed all bearings, seals, etc but kept the ring and pinion. It was $680 but I used all OEM parts.

 

[yoopercharged]

That is cheap...but I am assuming that is only labor? I had mine rebuilt a few months ago and changed all bearings, seals, etc but kept the ring and pinion. It was $680 but I used all OEM parts.

x2, sounds like a bargain.

 

[Kernal]

The $500 was just for labor and taxes; a master rebuild kit was something like $250 which is the four bearings, shims, seals, then add the seals for the rear axle and maybe bearings. As mentioned the mechanic I talked to hasn't ever worked on an Landcruiser diff or one of these E-lockers so I'm a bit uncomfortable having him do it. Thinking I might be better off just getting a complete 3rd, so I located a low mileage used 3rd and a new unused unit; any opinions what good prices would be for either?

 

[Tools R Us]

...
Tools: I was thinking maybe buying some time if it was just the front/outer pinion bearing, wouldn't have to pull the 3rd. What special tools are needed? Started looking for low mileage used 3rds if I have to go that route.

The biggie is a press with tooling, to push the bearings on and off. Doesn't need to be much of one, my old cheep 12T easily did the job. Also will need a dial gauge with holder to set gear backlash, a regular torque wrench, a beam/inch pound type to set pinion preload and something the hold the pinion flange when tightening the nut. For this I have a hunk (~3') if angle iron, with a couple of holes drilled, to bolt onto the flange.

If I were doing it myself, would inspect and likely reuse the carrier bearings. They last a very longtime, especially in the locker diff, they are huge. If paying someone to do the job, would likely replace all of them, for sure on a non-locker carrier, maybe not on a locker carrier.

 

[Tools R Us]

... it is only gets noticeable after 10-15 highway driving on a highway on a speed above 45-50. ...

That is a classic pinion symptom. It is one of those things where, the longer it is driven, the higher the chances of damage to other ($$$) parts.

 

[Kernal]

Tools; talked to a builder of diffs last night. He said I may be able to reshim the carrier bearings; like add .010 inch on each side, but then I don't have the tools or fixtures to hold the 3rd while working on it, and this is my daily driver. The longer I drive it the more wear I'll get on the ring and pinion which could make it difficult to set it up correctly later. I found a used rear 3rd and an unused unit, any thoughts on what they're worth? Thinking maybe pop one of the those in then take my time to rebuild this as a spare or sell it??

 

[Tools R Us]

Zuk's page on replacing pinion bearings: gear install

It is done on a mini diff, but the procedure is the same for '80 diffs, other than the rear locked unit. The e-locked unit is easier for this job, uses shims for the carrier, so just reassemble with the same shims in the same place and the backlash, gear pattern will be the same as before.

He always paints/checks the gear pattern. This is somewhat redundant, unnecessary, it is difficult/impossible to get a good "read" on used gears and if possible should be run where/how they were broken-in. So simply using the same pinion shim and setting the gear backlash back where it was is good enough.

 

[Tools R Us]

Tools; talked to a builder of diffs last night. He said I may be able to reshim the carrier bearings; like add .010 inch on each side, but then I don't have the tools or fixtures to hold the 3rd while working on it, and this is my daily driver. The longer I drive it the more wear I'll get on the ring and pinion which could make it difficult to set it up correctly later. I found a used rear 3rd and an unused unit, any thoughts on what they're worth? Thinking maybe pop one of the those in then take my time to rebuild this as a spare or sell it??

Is your diff an e-locker? It is a good idea to restore the carrier bearing preload when doing the job. The rear e-locked diff uses shims, all of the others are adjuster wheels. The rear full float unit is pretty easy to go in a day, don't even need to remove the wheels. The front is more work, pulling spindles, birfs, etc.

Zuk page on a rear '80 diff bearing replacement: gear install

 

[Kernal]

Tools; Thanks, I read through a few of those rebuilding threads; looks easy enough if you have the tools and fixtures. How do you remove the rear 3rd without removing the wheels?

 

[Tools R Us]

Tools; Thanks, I read through a few of those rebuilding threads; looks easy enough if you have the tools and fixtures. How do you remove the rear 3rd without removing the wheels?

On the full float, the axle bolts to the hub, so remove the nuts and cone washers, then slide the axle shaft out. Get under the rig, remove the rear of the drive shaft, tie it out of the way, remove the nuts around the diff, use a jack to pop it loose from the axle housing and man handle it to the ground. On lifted/big tire rigs I don't even jack the rig up. The e-lock diff requires a few more steps, lock the axle, wiring, etc, but both are simple to remove, just heavy. Before doing anything, drain the diff, or it will get messy!

 

[Kernal]

Tools: thanks; I do have the E-locker rear. OK, so leave the wheel on, just pull the axle shafts.

 

[Tools R Us]

Another advantage of the full floater is, it can be run without the diff. Remove the drive shaft, cover, tape up the hubs (bearings) and the diff opening to keep trash out, lock the center diff and drive in front wheel drive mode.