Rear Diff axel condition help

[stubble88]

Started to install my lift on the rear. Pulled everything off the axels and discovered this dark sludge with chunks of metal/rust. Splines had some surface rust towards the center but insert ends look fine. Just wondering what I should do. Is this a sign that water got in? Guess I’ll need to open the diff up now and check.
I can’t seem to figure out the picture attachment.
Thanks

 

[Apogee]

If you're looking at the axle splines, then you must have pulled the axles, correct? Assuming so, this would be a good time to pull the differential, clean everything up, install a drain plug and reassemble. New axle bearings and seals may also be in order. You're there, and how much will you want to do it a few months or years from now? Fresh gear lube never hurt anything.

 

[Redbark]

If you're looking at the axle splines, then you must have pulled the axles, correct? Assuming so, this would be a good time to pull the differential, clean everything up, install a drain plug and reassemble. New axle bearings and seals may also be in order. You're there, and how much will you want to do it a few months or years from now? Fresh gear lube never hurt anything.

Do you have a recommendation for the drain plug install, like location, plug type etc?

 

[stubble88]

Yeah
I’m doing it all.
Obviously moisture got i there so I’ll need to open the diff up.
And I guess I might as well convert to disc brakes
Thanks.

 

[Apogee]

Do you have a recommendation for the drain plug install, like location, plug type etc?

I just put an 1/8" NPT flush plug into the housing at the seem for the lower stamping. I thought about getting fancy, welding in a bung, etc, but the NPT plug was quick and easy and works great.

FWIW, I also run a Lube-Locker gasket on the differential, which makes installation and removal super easy and less of a PITA with respect to cleanup and RTV or gasket scraping. Best $26 I've spent on my rear end, and I've spent a lot between housings, Daytona pinion supports, gears, ARB, etc.

 

[SteveL]

Do a little research on the rear disc before you decide on em. Depending how you plan to use the bronco and how important is the e-brake to you. Between the caddy or explorer rear disc swaps the e-brake isnt great. Haven't heard opinions on the newer wilwood stuff beside being expensive.

 

[vintage bronco]

Yea to bad you are on the other side of the united states I have a complete HD 77 9in all new or rebuilt end to end with the big rear drum brakes & drain plug for sale.

 

[stubble88]

Carrier removed. Found rust on the biggest gear. All other components look fine. Bearing look good. No rust and look constantly oiled. Not sure what to do now.

 

[Justafordguy]

How much rust is on the ring gear? Can you post a close up picture of the rusted area?

 

[stubble88]

https://www.amazon.com/photos/shared/mQsMZFr-RtarkxWEjiVpug.6BYZziZHjjIPHuknkVPhZphttps://www.amazon.com/photos/shared/u4wCjBsKRLyAw04k0t58hw.Sf_FYVEYzhWoGpEoC8snpa
https://www.amazon.com/photos/shared/V14w8b6MSiOpxNv-aPZ0AA.-6bc31sWA2H6cFXTcq425j

 

[stubble88]

Carrier photos. Thanks

 

[Apogee]

FWIW, I've seen worse run just fine. You could clean it up with some Scotch-Brite pads, wash it down with brake cleaner, check the pattern and if it's good, run it. If there isn't any significant pitting, I'm not sure you'd notice any difference, but if there is, then you may just get some additional noise and accelerated wear. What's the worst case scenario, you fail the gears and need to replace them and get a master install kit? Alternatively, you could proactively do those things and spend the money no matter what, versus run what you've got and find out how it does.

Just saw the pictures above while I was typing this response...pitting looks pretty bad, but it's towards the heel, so depending on the pattern, still may not be a major issue. If it was mine and I wanted a different gear ratio, this would be the excuse to make it happen, otherwise I might look for a set of used take-out gears to run.

 

[Rustytruck]

If it was mine i would run it until it gets noisy as long as the bearings show no rust.

 

[stubble88]

yeah
going to run it
trying to figure out what seals I should replace.
Is it just the spindle seal? Or do I have to remove the bearing on the end and replace that stuff?
need to keep moisture out.

 

[stubble88]

theres supposed to be an ID number on the back of the pumpkin. I cant see it anywhere. How else can we ID our Diff?

 

[WILDHORSES]

theres supposed to be an ID number on the back of the pumpkin. I cant see it anywhere. How else can we ID our Diff?

Way back in the day there would have been a tag on the front of the third member under one of the nuts holding it into the housing. No big if it's gone. I don't trust them anyway I have seen people leave them on even after a gear change.%) It's an open diff. Count the teeth on the ring and pinion and divide the pinion into the ring for gear ratio. That's about all there is.

Jim

 

[stubble88]

I have the tag. But when I called TBP the tech told me there was s number on the back. Then he can send me the correct bearing and seals. Might need to talk to someone else
WILDHORSES, can you send me a link or part number from your sight?

 

[Viperwolf1]

I have the tag. But when I called TBP the tech told me there was s number on the back. Then he can send me the correct bearing and seals. Might need to talk to someone else
WILDHORSES, can you send me a link or part number from your sight?

The axle tag says it's a small bearing axle. The RAWR also indicates a small bearing axle. Chances are it's a small bearing axle.

 

[WILDHORSES]

I have the tag. But when I called TBP the tech told me there was s number on the back. Then he can send me the correct bearing and seals. Might need to talk to someone else
WILDHORSES, can you send me a link or part number from your sight?

Based on what I see in those pics here's the rebuild kit for your 1973 Ford 9" third member. Axles bearings and seals also available.
https://www.wildhorses4x4.com/product/Third_Member_Rebuild_Kit_7077yr/bronco_Rear_Differential

If you are going to tear the diff apart I would swap it out to something that will give you a real 4 wheel drive. It's kind of the snowball effect that ends up at a large bearing 31/35 spline Locker, Dura Grip, ARB etc.

Jim