Differential question

[Zeroman]

So, I picked up a used differential a couple of weeks ago. Ring and Pinion gears look in great shape, but it was in pretty sad condition on the outside...rust, dirt, etc.

I pressure washed it, sand blasted it(now I know why people pay "other people" to sandblast!), primed, and painted it.

Planning on popping the cover back off of it again, pulling the axles, replacing the axle bearings and seals, and replacing the pinion seal.

Should I "flush" the differential and clean out all the old gear oil, and possibly sludge, that does not drain out? If so, how should I do it? Do I use a solvent? What kind of solvent?

Anyway, thanks in advance for any advice.

[obijuan]

a good couple cans of brake cleaner will do well. run a couple rags down the tubes with a broomstick or something.

[Fitz]

Originally Posted by Zeroman

So, I picked up a used differential a couple of weeks ago. Ring and Pinion gears look in great shape, but it was in pretty sad condition on the outside...rust, dirt, etc.

I pressure washed it, sand blasted it(now I know why people pay "other people" to sandblast!), primed, and painted it.

Planning on popping the cover back off of it again, pulling the axles, replacing the axle bearings and seals, and replacing the pinion seal.

Should I "flush" the differential and clean out all the old gear oil, and possibly sludge, that does not drain out? If so, how should I do it? Do I use a solvent? What kind of solvent?

Anyway, thanks in advance for any advice.

Mineral spirits won't attack the axle and pinion seals but it will dissolve the sludge and help you flush it out.

[Zeroman]

Thanks sounds good.

I did remove the axles and found an amount of rust on the passenger side axle about midway down the axle. This diff has not seen use in some time. Lots of crap in the tube, and it appears to go all the way up to the carrier bearing. Not happy about that.

I finally spoke with my brother who is a life long mechanic. I asked him about cleaning out the diff and checking the carrier bearing, and he told me I could remove the carrier and pressure wash it as long as I kept all of the bearings, shims, etc. in the same direction and order.

I have replaced the pinion shaft to keep the side gears and differential pinion gears from dropping out, so I guess I am going to give it a try.

Any thoughts?

[mechanicalman]

If this is a half ton axle, I'd think twice before I replaced the axle bearings. Remember, the inner race is the axle itself and the bearing is "worn in" with the axle. If you replace the bearing, it will "wear in" to the old axle, and that actually will likely not live as long as the old bearing. No doubt some will say they have done it no problems and maybe true, but I'm 100% sure what I'm saying.

If there is a groove on either axle, you need to replace the axle, then you need new bearings.

Also, before you replace the pinion seal, I'd recommend FIRST setting the pinion pre-load to minimum drag spec, mark the pinion nut/shaft with a cold chisel, then when you replace the seal just tighten the pinion nut to the mark. If you replace any bearings then you need to start over with new crush sleeve.

Also, if you remove the carrier (makes it easier to set pinion pre-load anyway), be very careful trying to wedge it back into the carrier you might need to rent a "case spreader", although an experienced mechanic can likely work it in for you. If it slides out easy, then it needs re-shimmed anyway or maybe new bearings. You would need a dial indicator to check gear end-play and pull a "pattern" BEFORE and AFTER. A mistake here could kill the diff.

If it's been sitting a long time, the oil will absorb moisture from the atmosphere and sludge will form. Cars that are driven all the time get warm and keep it cooked out. It might not pay to dis-assemble everything if you can simply remove the crud with chemicals as long as you don't get any metal dust from inside the diff that would indicate extreme wear. Just make sure you soak all bearings with lube before assembly and don't forget to fill it. Also, if it's a "posi" don't forget posi additive.

[Zeroman]

mechanicalman, thanks for the info.

When you say "groove" on the axle are you referring to noticeable wear on the axle, or an actual groove?

So your opinion is that i just clean and re-grease the bearings and put them back in after I get everything cleaned out?

[mechanicalman]

Originally Posted by Zeroman

mechanicalman, thanks for the info.

When you say "groove" on the axle are you referring to noticeable wear on the axle, or an actual groove?

So your opinion is that i just clean and re-grease the bearings and put them back in after I get everything cleaned out?

You can always see where the bearing has been riding, but if it feels rough when you run your finger across it, and if you can see lines on the bearings, it's likely not in good condition. Actual groove is real bad, and can result in a sheared axle.

If you haven't/don't get more than a TINY amount of metal shavings from out of the diff, I'd recommend NOT taking the carrier out, just flush everything out as best and finish with brake clean also flush the pinion bearings while you have the seal out; it evaporates well. Now, bearings are kinda dry so after you put your axle seals in, squirt gear lube into the axle tube until it spills over the axle bearings then re-assemble. Before you take it off the jack-stands, fill the diff and turn the pinion over and over working the lube into the bearings. Then, if nec., top it off.

Before all this oily work, I like to glue the gasket to the cover and gently bolt it on and get the sealer to dry; then when you do final installation the gasket is less likely to split, cause it's hard to get the gasket surface to stay dry on the case side long enough to slam the cover on.

[mechanicalman]

Let me know what you come up with if you have any more concerns. If you are not sure about the axle wear, maybe you could take some good close-up pictures.

[Zeroman]

Well, the axles are toast. The bearing surfaces look good, but the sealing surfaces are badly pitted. I guess I know why moisture got in the axle tube. I had not really intended to use these axles, so no loss, except I had hopes to get it buttoned back up so my wife could park her vehicle in the garage tonight. Oh well, so much for that.

I did pull the carrier as the amount of crap in the passenger side axle tube worried me. I am glad I did, as the carrier bearing races were a little pitted, so I guess I am in for some more expense.

I ended cleaning the tubes just like cleaning a rifle barrel. I kept pushing a wet patch then a dry patch until it was cleared up. Then ran an oil patch down each tube. Biggest bore I have ever swabbed.

I cleaned and lubed everything in the carrier assembly and put it back just as it came out.

I did take pics, but I need to discuss the situation with the person I bought it from, so I would rather not go any further.

Thanks for all the input.

[mechanicalman]

Sounds a little sketchy. Probably rebuild-able, but maybe a re-negotiation would be in order on the price? Let me know if you do I'll walk you through it, let me know before you start.

If the carrier came out and went in easy, that's indicative of worn side bearings. Carefully inspect the gear mating surfaces of you intend to re-use the gears.

Sounds like at least new axles/bearings, all new side and pinion bearings.