This is an area where I don't have any inspection/rebuild experience.

I'm about to get a used GM 10-bolt housing, including gears and axles. Suspension brackets are already welded on for a T-Bucket. I have no idea what condition the housing and guts are in, nor will I know the gear ratio until I can pull the cover. I can return the unit if its a disaster. I am willing to put some money into this if the foundation is good. Engine / trans is 350/TH350, about 300 hp.

I'm looking for those who are experienced in this to offer some advice on how to go about getting the unit checked out and what to look for. I'm willing to do all the work on it, but I haven't done this type of work before and I want it done right after all is said and done. Could be a great learning experience. I'm assuming I'd want to check for a straight housing, straight axles, and ring/pinion and bearing condition if I'm going to keep the gears it came with. Anything else? If I decide to take it to a shop, what should I expect to pay to have it checked out, and perhaps rebuilt?

Also, how should I go about refinishing the exterior of the housing (I'd assume exterme rust on the housing except in the area of the welds for the brackets) and what would you use to make it look good?

Many thanks to all.

If the rearend is assembled bolt some wheels and tires on it and take some toe measurements from the front, top, and rear, of the tires to see if this thing is straight. Rearends that have had welding done are usually bent if it was done wrong, the cooling action of the weld will pull the axle tubes. People do it all the time thinking everything is fine then they have spider gear problems and leaking axle seals down the road. Been there.

Cucumber definitely has the start! Then:

1. Does everything turn easy? You should be able to support the axle and turn a wheel easily. Pinion shold turn, and if it's a standard diff the opposite wheel should turn in the opposite direction. Should be no noise, but if it's a bit still could be brakes dragging, so check.

2. When you pull the back cover inspect for wear. The pinion shoud be wearing right near the center of the teeth of the ring gear. If the teeth are sharp on the edges it's worn to much!

3. Check for rusting/pitting. Dump it if there is any! A little surface rust that more or less wipes off is okay.

4. A little brownish slush means water in the oil. That's not real bad, can be cleaned. As long as no rust/pitting...

you can count the teeth on pinion and ring gear for ratio, check out spider gears for wear, and all gears

You can rotate the pinion counting the turns per one turn of the tires, or if you only turn one tire, 1/2 the turns = gear ratio. (remember if you are spinning one tire, it is turning twice as fast as the speedometer says)

A big time Thank You to all who replied. These are some excellent suggestions and easy to do.

Anybody have any ideas on how to make the thing look good after it is checked out / repaired? Are grease removers or metal preps bad for the seals? If necessary, how much grinding will the housings take? Are POR-15 products a good finish? This is a T-Bucket, so the housing will be largely visible and want it to look good (chassis will be painted black).

Thanks again to all.

I love por15 products. Kinda expensive but for frames and undercarriages I would rather put por15 than powdercoat.

farna.... why is more than just a little rust inside the pumpkin bad?? I just bought a rearend out of a 79/80 TranAm it has rust inside along with grit. I've gone through about 3 cans of parts cleaner andseveral wire brushes it look pretty good now. I believe this rearend was supposed to have a vent tube on it that was either lost or removed that allowed contamination inside. I'm going to give this cleaned assembly a whirl. What is the worst that could happen??

I sand-blasted, primed and painted mine. The next step is to thoroughly disassemble and wash it out with varsol ... I'm expecting to find SOME sand and I really don't want that!

While doing that I'll carefully inspect the bearings for pitting, replace the pinion and axle seals, etc. I have a sight advantage on you as I have owned this truck since 32,000 (easy) miles and it has 70,000 on it now. I never saw any leaks or heard any noises ... so I'm sure it's all good.

Attached Thumbnails

   

worst? eat up all the guts and bearings...

if its the bare housing, i would wash it out with hot water and dish soap, rinsing extensively.... then WD 40.

That's a good tip "x" ...
I recall our (ex) machine shop guy saying the same thing about engine components. Soap and water seem to lift things and move them better than solvents.

Perhaps a combination of both? Varsol to dilute the oil and dissolve the heavier crap, followed by the soap and water?

Ive removed the carrier and axles and removed all signs on contamination. Thanks for the idea on soap and water. I'm assuming rinsing with a 1500psi powerwasher doesnt hurt either. after the cleaning i wd40'd everything down real well internally. I cleaned the carrier the best i could but there is some slight pitting on the ring gear from where the gear sat above the oil level. I polished the gears with a 3m burnishing wheel and a high speed die grinder. It cleaned up pretty good but there is still a shadow on the gear. is it bad?? Also, how hard is it to replace the spider gears?? there appears to several that have been "traumatized" by the contamination I'm guessing a piece of gravel. One other question. Are these rearends supposed to have some type of venting mechanisim? There is a hole approx. 3/8" big on the side of the pumpkin with nothing in it. I"ve tried to find a diagram or picture but no luck. I could send pictures to anyone who would care to help out. Thanks for all your help.

Here are some pics of my 12-bolt GM truck diff, and I think the 10-bolt is quite similar.

Removing the spider gears is quite simple...

Start by removing the locking bolt, then the spider pin.
Push the axles in, remove the c-clips and pull the axle shafts back out of the way.
The spider (small) gears simply roll out, and then the side gears (larger ones that the axles go into) will simply pull out. There is one thrust washer behind each of the 4 gears, which usually stick to the case because of the oil surface tension ... so make sure you get them all out and replace them as well. Assemble in reverse.

Attached Thumbnails

     

66GMC - It sounds like you have prepped and painted the housing exterior before disassembly and repair (if necessary). In my mind, it seemed logical to paint it after all was reassembled and just prior to final installation. By the way, it looks great and that's the finish I'm looking to achieve.

Well yeah ... that's probably the way I should have done it, but summers are short here, and I wanted to get all of the blasting and painting done outdoors.

One argument FOR doing it this way is the inevitable intrusion of sand ... cripes that stuff gets EVERYWHERE. I'm sure that I'll find some in the vent.

I used some really tough paint, so I'm hoping that it will withstand the cleaning and re-assembly process. If not ... meh, it's just chassis stuff. My main intention was to eliminate and discourage rust.

Somewhere along the line, I got the bright idea to splash a lot of color on these components. Some folks like it, others think I'm nucking futs! See my journal and/or poll "Bright colors on chassis parts"

Don

Thanks 66GMC nice photos!!!! Yea I'm missing the vent piece I'll definetly replace it!! I like the bright colors, but I'll stick with por15. I still have alot of work to do. I guess the next big step is to remove the spring perches and get ready for the 4 link.

Thanks Again!!