My speedo gave out a while back, so I removed it to find this:



Today I finally got around to opening the rear differential to see what ground my speed sensor and this is what I found:

Teeth ground down. Is this the tone ring? There is a loose bolt just sitting in a hole too.


Note the random bolt in the nook to the left.


Metal shavings on the cover magnet.


How do I go about removing the differential? What part has the ground down teeth, and what are the random loose bolts for? Should I replace any bearings while I'm at it?

 

The ground part is the tone ring. The bolts are likely ring gear bolts. Pull that other loose bolt out, pull the axle shafts and driveshaft, do a backlash check and pattern check before removing. If the backlash and gear patten are good, and the bearings are ok, then you could just install a new tone ring and new ring gear bolts. Make sure they are torqued properly.

Is there a bolt head inside somewhere to go along withe the bolt thats missing one? Looks like that other bolt thats tucked away is also missing a head.

 

with all the metal filings,i would replace the bearings and seals also,in my opinion i think he needs a pro to put it together properly

 

That rear is trashed. Maybe save the gears, but full rebuild time for sure.

 

I agree with Tate, it cost nothing to clean it out and do a pattern, if it's good then their likely isn't too much damage yet, and if the bearings are good a tone ring and some oil is far cheaper than a full rebuild or replacement.

 

I will be interested to see how you get the tone ring replaced while maintaining whatever gear pattern it is showing now.

 

No bolt heads. They were completely smooth and appear to have been made that way.

How do I do a backlash and pattern check? My Haynes book says nothing about differentials, so I have no removal/installation or torque values to work with.

Is that an offer to help? I'll supply the beer, or in your case the coffee.

How much am I looking at for a rebuild? My truck is no purdy thing, and has a lot of miles on it. I'm looking to do things on the cheap when possible, and I am good about following directions and figuring things out on my own.

Hopefully this is all I need to do. Where should I get a tone ring and bolts? I'll update on my progress and include more pics if I find anything interesting.

 

I've found out that Haynes manuals aren't really that good to go by. If I were you, I'd purchase a factory service manual for your year of truck. It'll cost you more than a haynes manual but it's well worth the investment. You can buy one at genosgarage.com or any dealer.

 

If the gear pattern IS still good then it likely hasn't caused a lot of damage as a small amount of damage and wear would throw the pattern off. IF the bearings are still good and do not require replacement on dis-assembly then a tone ring change keeping track of shims should be reasonably straight forward and not that expensive if having it done. The pinion would not have to come out and the shimming would not change so the gear pattern should remain the same.

 

So you're going to tear it down and put it back together with the same bearings and pinion seal? After seeing it looking like that?

Go for it!

 

If the pattern changes, so will the backlash. As the backlash is put back to disassembly specs, the pattern will also come back.

Replace bearings as needed. If there is no damage, I would run them again. Thats where an inspection is needed. Pull the pinion and inspect the bearings and replace the seal if needed.


redpoint, if you do a search on google, you will find instructions on doing a backlash and pattern check, as well as torque specs. You can also find the '01 service manual on line, which will tell you how to do it as well. You'll need some gear paint and a dial indicator to do it.

 

1998.5 I would be looking for a diff at wrecking yard. The cost to properly rebuild that diff could run you more money then the truck is worth. Dana diff's use shims to adjust bearing preload and gear backlash. Diff overhaul shop would need all setup tools to properly set up a new gear set. If they don't set gears up properly it will be noisy or just not last many miles. Gears, bearings, posi unit, tone ring, shim kit, and is your housing damage?? I have seen many of those Dana 70's spin the races in the housing which destroys the machined surface making housing unusable. The clutches in posi unit are probally burnt out by the looks of your gear oil color. Have someone experience with diff overhauls check it out for you first and get prices first also. Factory replacement parts will be more expensive then aftermarket parts.. Good Luck.

 

My point is the whole unit is suspect, based simply of the looks of it. The fact that it came apart like that in the first place should tell you something that no amount of inspection will. Why risk the time/money to do it over a 2nd time after if fails for re-using contaminated/damaged parts? The job will be the same hours with new parts.

But hey, it's your rear, your money. This is probably the best advice yet:

 

If you look for a used diff at wrecking yard there are a few things you need to look for before buying. Make sure diff is same gear ratio, gear are always marked with ratio. Pull cover and check backlash of ring gear. Used diffs with high mileage will have excessive backlash and gears could be noisy. So stay away from high mileage diffs. Also check end play of posi unit in housing. There should be no endplay at all. If the carrier moves at all from side to side stay clear of that diff. Most likely the bearing race has spun in housing and just a matter of time before this diff is junk. Metal found on magnet in cover is your first clue. There shouldn't be any. Black burnt smelly gear oil means clutches are burnt out. Not using posi diff additive or using two different size tires on rear axle will burn up clutches. Turn the yoke by hand it should be smooth with no roughness felt when turning, there should be a slight drag and no movement in or out the seal should not show sign of leakage. You can run a pattern check also brush some gear pattern compound on gears. Pattern should be centered on gears, both coast and drive side. If not gears might be noisy howling sound while driving.

 

nice info bigiron