Today coming from church, I heard a screech/grind coming from the rear end. I was maybe 1/4 mile from my house, so I drove it home. Disconnected the driveshaft, and it turned with great difficulty. Pulled drums off, threw the tire back on to help turn it, and it still turns hard.
This is an 8 3/4 which I thought were indestructible

wondering what should I look for when it comes apart?

Any common problems? This is my only ride, and I kind of want to get parts before I pull it apart.

Difficult to diagonse until it is apart, assuming it was full of gear lube, the most common problem is the axle bearings.

They are lubed with bearing grease, not axle fluid. Be sure to repack them with putting it back together.

which case is it 741,742,489?

on the front of the carrier, there will be a bunch of cast numbers. The last 3 digits will tell you what type it is. Most stock vehicles got #489 cases from 1969-1974.

If OE it'd be a 489. Might score an open 489/471/472 for cheap to get you up & running then you can fix yours at your leisure. Just make sure the one you buy if you go this route has the same u joint, only 2 choices 7260 or 7290 so it'll be an easy bolt in. You may go with the better clutch type sure grip (742/741) rather than the 489 if yours is too badly damaged. Holler how it turns out

Just a reminder that all 8 3/4 differential assemblies, either open or Sure Grip, interchange between all five housings (the 741/742/489/657/XXX part). Only the bearings are different

So you can put a clutch type unit into a 489 case or a cone type into a 741, etc.
R.

I'd check to make sure the pinion nut is tight, if not then you got bigger problems.

My '71 donor truck had a 741 in it stock. They didn't waste 742s or 489s on smallblocks or slant 6s. And if it had been ordered with a Sure Grip it would have had a B-W SpinResistant which we know as the cone style.

R.

the stamp will be on the drivers side front of diff.,hopefully you have the 742,it has bigger components.

Right. Assuming it is a stock rear end, it's either a 741 or 489. Assuming it's a stock rear end it has a cone-type Sure Grip that was called a SpinResistant by Borg-Warner who manufactured it. When Chrysler sold it to the public in a vehicle they called it Sure Grip no matter what style it was, that was their trade name. Now, if you were buying a new replacement it would be an Auburn as they manufacture the cone type these days.

So unless your '72 truck is a factory bigblock, it has a 741 housing with a cone-type Sure Grip in it. If it was a factory big block it would have a 489 case with a cone type Sure Grip.

As the cone type wears it grinds off little particles of metal which circulate with the oil. So what JohnRR was saying is that no matter what else you do to your rear end, you should plan on cleaning out all of the old oil and particulate.

Now, on to the "stamped" versus "cast" numbers. Casting numbers are cast into the part, NOT STAMPED. Stamped numbers usually go on a surface that has been machined off and are pressed into the metal in the stamping process. Casting numbers are part of the mold into which the molten metal is poured and are there when the part is taken out of the mold. Axle housings or carriers or pigs or whatever else you call them, are castings. As such they have casting numbers. These are on the forward side of the housing going in ghe same direction as the pinion. Occasionally there is a housing without a casting number but this is rare.

R.

And to complete the trifecta, forged rods have FORGING NUMBERS! Now I'll stop whining.

havent had time to look yet, sorry guys.

i'm pretty sure its a stock rear end. the original owner wasnt known for his mechanical abilities, and my grampa nor I has ever swapped it out.

thanks for the knowledge guys

I got the next couple days off of work, and I'm doing a motor swap to earn some extra funds (GM 2.2 in a 96 s10...FUN)

I hit up the pick a part today and got a sway bar among some other goodies, and am going back for more tomorrow. I have to get some stuff for the 2.2 swap and as a side I am stopping and getting more parts for my truck lol