8 3/4 Rear End - General Questions, Seek all and any help, 1st restore!

[MThedford1]

I have some general questions and am hoping for some guidance as I rebuild my 8 3/4 rear end. Personally I'm on a budget and limited on tools so I am really hoping to work with what I have and only replace what is absolutely necessary.

My first questions are in regards to my 489 case. I don't think I have the Sure Grip setup but I haven't been able to confirm nor deny. I have posted some pictures to help identify if its a Sure Grip. Can anyone help? I am also questioning the wear on the teeth on the inside of the gears. They appear to have proper engagement but I've read that engagement is something that cant really be seen. Would anyone suggest putting marking paint to view the engagement? If so, where would I apply the gear paint in order to see the engagement of the teeth inside of the gear setup? Also, do the teeth look to be in good shape? Or do they are worn to the point they need to be replaced (hoping not). What would you guys do? Do you think this is something that you would clean-up, assemble, and run? Or would you guys do a little more? Everything seems to spin smooth as butter, I don't think the bearings have any issues or anything of that sort. What would be the best way to clean this? Purple Power? Brake Cleaner? I will soak parts in oil to give them life again. The attached photos appear repetitive but I am spinning the gears allowing you to see all of the teeth. They are very uniform which is why it appears as the same photo but they are slightly different. Some teeth appear to be gouged and scratched but its residual oil. They are pretty clean and uniform.

I am also unsure of the T-block, or Y-block that was screwed into the rear end housing. It was attached to the brake-lines but its a direct hole into the rear-end housing/axle. Does anyone know how this works? I plan on doing a disk brake conversion all around and will not go with drums. Is this something that I will still have to use when I switch to disk brakes? I'm not sure how that works at all so any info would be greatly appreciated.

This is my first build so I'm hoping for some direction. Some of this is completely foreign to me so I'm looking for all the help I can get. Thank you in advance guys!

 

[4spdragtop]

Watching, hope to learn something. Good luck.

 

[Outsder]

Pics of Open Diff, not Sure Grip. Well the T block on top the housing multi-purposed. You need a flex house going to rear T block for a stock spring application because the rear moves, you need to split from one feed line to two lines, R & L side brakes, and the top of the hold down "bolt" is a vent for the housing.

Are you just wanting clean things up or changing gear ratios. If changing ratios you will need a dial indicator, diff side spanner adjusters and other items.

 

[MThedford1]

Pics of Open Diff, not Sure Grip. Well the T block on top the housing multi-purposed. You need a flex house going to rear T block for a stock spring application because the rear moves, you need to split from one feed line to two lines, R & L side brakes, and the top of the hold down "bolt" is a vent for the housing.

Are you just wanting clean things up or changing gear ratios. If changing ratios you will need a dial indicator, diff side spanner adjusters and other items.

Thank you for this useful information. That makes a lot of sense. The feed line needs to be rubber-like to allow for flex as the rear suspension dampens and springs back up, thank you! Do you think I would be okay with cleaning this rear end, redoing the seals and letting her rip? I feel like the side gears and spider gears are worn but will be okay to run. Last thing I would hate to do is put it back together and then have to re-do it after it blows out. What would be your call?

 

[Outsder]

Can't really tell the gear condition from your pics, angle, light or something or maybe it's just my old eyes. However if the gear faces aren't pitted and there is no tooth set wear that you can feel with your fingernail the gears may be good.

Differentials are pretty durable and if it rotates freely, the pinion seems captured and there is not excessive backlash ( .006" - .012") between the ring and pinion gear, (this is where you need the dial indicator), then it might be good to go.

If there is dirt on the gear assembly from sitting uncovered in the open, you can probably clean it with something petroleum based like ATF in a spray bottle or something, but when you're done coat everything with new gear oil and bag it if you are not soon going to install, fill with oil and drive it.

 

[Jerry Hall]

Hold the ring gear tightly and move the yoke one way then the other. If there is any movement more than a 1/8" before the ring gear tries to move then it may need attention. If as you say, it spins smoothly and you find no excessive movement between forward and reverse, just clean it as previously described, reinstall and run it.

 

[Jadaharabi]

If you replace the pinion seal you will be removing the nut off the pinion and taking the yolk off. Inside behind that bearing is a crush sleeve. If you take and loosen that nut you will probably be needing a new crush sleeve which means completely disassembling the differential to replace it. Therefore if that seal doesn't leak I wouldn't mess with it. Also was the rear end making noise. If it was then it could be bearings or it could be teeth on the gears or it could be several different things causing that. Personally if it's not broke don't fix it. 
Hang it up and spray it out with some PB Blaster. I'll let it drain then shoot some oil in there to lube everything up, bag it and tag it until you're ready to use it.
Jmho

 

[Oldmanmopar]

The housing is a 69 or earlier due to the brake line location

The through hole is for a vent bolt the holds the brake line on

You rear is an open rear . Not a (sure grip) or (trac-lock)

Clean it out with Super clean. Blow it dry with air. Then get a three cans of brake clean and spray it out. do this while rigght sid up and the yoke tilted up so the debree flows out/

Once clean soak it down with yoke facing downward and spin it to disburse the oil into the bearings.

Bag it and stand it up in a 6 gal plastic bucket and put a lid on it.

If it was mine I would buy a used sure grip and throw it in . The cone style that came with the 489's are cheap I seen them for $50 - $100. That is what would have came in your 489 carrier. The cone style is smoother in sharp turns for the street.

The clutch style that came in the 741 and 742 are more desirable for performance use but cost more. .