Help with Rear Axle

[PDXk5]

I have a 1972 4wd Blazer. The original axle has developed a leak where the axle tube is pressed into the differential housing. It sounds like it will be easiest to just replace the axle assembly rather than trying to have someone weld the seem ( from speaking with others here on the forum, it is possible but difficult to weld, as the tube is steel and the differential housing is cast iron).

Anyway, I was able to find an axle assembly here locally. I have purchased it and am now trying to figure out what exactly I have bought. According to the seller its out of a '72 4wd Blazer. I pulled the differential cover. The larger gear has 3 73 GM stamped on the edge. I haven't opened mine yet so am not sure what ratio I have. My axle is original to my rig and is equipped with Posi. I'm hoping to keep the rig with the same gear ratio and posi as it was originally.

With this in mind, I'm new to this and have a few questions, I'm hoping someone can help me with:

1.How do I tell if the 'replacement' rear end is a Posi unit?
If I spin the pinion both drums turn in the same direction. I thought this meant it was a posi unit. However, just spinning the pinion, sometime I would stop and when I started spinning again only one drum would spin. Stop and then start again, and then both would spin. Does this mean it's worn?

2. When I removed the diff cover I noticed a bunch of chunks of metal. One piece looked like a small spring and the others looked like gear teeth. I spun slowly the pinion and looked at all visible teeth in the differential and didn't notice any broken or missing teeth. What and where are these from?

3. I was wanting to upgrade the drums to the HD style that are 2 1/2 wide. I'm having a hard time finding an original OEM set up at a local salvage yard. Any suggestions? My understanding is the 11 X 2 1/2 drum brake was available from '77 to '91.

4. Shall I attempt to disassemble, reassemble and install or will it be more advisable to obtain all the parts and take it to a shop to put everything together and install on my rig? New bearings, seals, paint and installation... Any suggestions for a local shop? Any estimates on cost? I don't have to do this right away. My axle works great, it just leaks on my garage floor.

Thanks,
I appreciate your help.

[PDXk5]

Not sure, why it's not letting me attach more than one photo at a time. Photo 2

[PDXk5]

Photo 3

[PDXk5]

I should have spun it a bit more and taken a photo as the open portion of the assembly came into view.

[outfield]

Since you are in Portland I think I can help. I suggest calling 6 States Distibutors on Columbia Blvd 503 249 1010 and see if they can transfer the gears from your old axle to the new one. This way you know the gear ratio will match and the broken diff will go away too.

[PDXk5]

Originally Posted by outfield

Since you are in Portland I think I can help. I suggest calling 6 States Distibutors on Columbia Blvd 503 249 1010 and see if they can transfer the gears from your old axle to the new one. This way you know the gear ratio will match and the broken diff will go away too.

That's a great idea, thanks! I hadn't thought about them. They helped me with parts for my locking hubs.

[LockDoc]

-
The 11- 41 indicates 3.73. It is not a posi. Not sure where the pieces came from.

LockDoc

[truckster]

Those look like pieces from a Gov-Loc. I'll bet the rear grenaded and the owner put in open gears without cleaning things up thoroughly.

[outfield]

I think you're on to something there Truckster!

Originally Posted by truckster

Those look like pieces from a Gov-Loc. I'll bet the rear grenaded and the owner put in open gears without cleaning things up thoroughly.

[MikeB]

Before you spend any money on the new axle assembly, make sure overall width is the same as what you have. Then, as suggested above, your best bet may be to install your existing internals components in the new housing.

If the ring and pinion gears in the new axle look OK, you may be able to sell them. Unless severely abused, 12-bolt truck gears will last 100s of thousands of miles. When I added a posi unit to my 69 C10's 12-bolt, the original gears still had proper backlash and looked like new. I replaced the carrier and pinion bearings, but probably didn't need to.

BTW, a posi looks something like this, and uses clutches or cones instead of spider gears.

[BILT4ME]

Also, measure the spring pad locations and look at the shock mounts. It appears to ME that the rear axle in the picture is from a 2WD leaf spring truck based on the shock mount locations.

I hope you didn't pay much for that axle assembly, because you didn't get much.

Why not seal that area with caulk. There is a rubber sealant from the local FLAPS that is a rubber based "spray" can in black (it's NOT Permatex black) that is oil resistant and dries in 10 minutes. Clean the area real well with brake cleaner and goober it on, smear it smooth with your finger. You could also do the same from the indide, but you should remove the carrier first to access the area on the end of the tube.

Good Luck!

[PDXk5]

Thanks for the comments guys.

I measured my axle assembly and then the donor. They appear to match. I don't know if there are subtle differences in dimensions between 2wd vs 4wd axle assemblies but these two measure approximately:

58 inches backing plate to backing plate.
43 inches from outside edge of spring perch to outside edge of spring perch.
27 1/2 inches from outside edge of shock mount to outside edge of shock mount.

They both have the 6 lug drums so I think they match.



I called 6 states Distributing, it sounds like they can hook me up.

I spoke with a guy who walked me through what they could do as follows:

1. Hot dip donor axle - removing, dirt, grease and rust down to bare metal
2. Disassemble the donor axle housing
3. Remove existing internals from my axle
4. Install new bearings and seals
5. Install my original posi unit and axles into the donor housing
6. Paint entire axle housing and drums
7. Install new stainless steel brake lines with spiral wrap protection
8. Reinstall on my rig

He indicated the hot dip process would take 2 days and the rebuilding of the axle (swap with my internals), removing my axle and reinstalling the new rebuilt unit would be an additional 2 days. They would dip/soak the donor and once done, I could bring my rig into for them to do the swap. So they would only have my Blazer for 2 days.

I told him, I was looking for a source for the heavy duty 11x2 3/4 drums and backing plates before I would be ready for him. He said they could include that install in the effort, if I brought them with the rig.

He also stated that he could make the brake lines or I could purchase them and he would install (I was looking at Inline Tube pre bent stainless steel brake lines). He recommended getting ones that looked stock. Their paint 'process' is a black gloss rattle can paint. He said, he could get whatever paint I wanted but it would be rattle can.

I asked him for an estimate, he said he would budget $1,200.

What do you guys think? It would be like a new rear end (good for another 40 + years). I'm thinking of doing it. Any comments, suggestions?

[BILT4ME]

Yes, that's worthwhile with them cleaning up the entire rear axle and painting it.

I just got done doing something similar but installed NEW gears and NEW bearings, and a NEW Detroit locker. My cost was $2500. And I had to paint it and take out of the truck, then put it back in the truck and make my own brake lines.

The labor and new bearings/seals was about $1000.

Measure the pads and such on your truck first to make sure they are the same. You can check the numbers stamped in the axle tube on the right tube to determine if they are the same or similar to the ones already on your truck.

[truckster]

Before I would go that route, you really should know what kind of posi unit you have in your current truck and what kind of shape it's in. If it's a true posi and it's in good shape, I'd go for it. If it's a Gov-Loc or it's worn out, I'd spend the money to fix it now.