'77 FJ40 Front Differential Cleanup (1 Viewer)

[kerryjcox]

I am redoing both knuckles on my '77 FJ40. I also decided to crack open the front differential and just check for signs of wear or any breakage. Everything looks good.
Couple questions:
1. The differential fluid was a gray sludge due to leakage of grease from the knuckles into the differential fluid. What is the best way to clean everything out of the axle and off the differential itself? I have just been using a clothes hanger with some lint-free paper towels and rags and running the end up and down the axles.
2. Should I worry about taking apart the differential itself and restoring the pinion? I am still a newb when it comes to this. I figured I would get all the sludge out and then fill it all back up with new diff fluid.
I am attaching a few pics to clarify.
The differential itself looks in good condition. Just need to get it all cleaned off. I removed the old gasket and have a new replacement from CruiserTeq ready to go.
Suggestions on sealant?
While I have it open, just wondering if I should worry about the pinion and do any replacing there?
Thanks in advance.

 

[SteveH]

You are at risk of worrying about this too much! If the ring and pinion wear surfaces look good, I would re-assemble and sleep well. Do not disassemble the ring and pinion. The front diff sees very little use/wear on a truck with locking hubs. The 'sludge' is knuckle grease that migrated into the diff cavity over the years, due to overfilled steering knuckles. It's grease with Moly Sulfide in it, and won't hurt a thing.

Now that you have taken it apart, wipe off the worst of it, reassemble the axle and fill with gear oil, and drive it with the hubs locked. This 'sludge' (harmless) will eventually migrate into the gear oil.

 

[kerryjcox]

You are at risk of worrying about this too much! If the ring and pinion wear surfaces look good, I would re-assemble and sleep well. Do not disassemble the ring and pinion. The front diff sees very little use/wear on a truck with locking hubs. The 'sludge' is knuckle grease that migrated into the diff cavity over the years, due to overfilled steering knuckles. It's grease with Moly Sulfide in it, and won't hurt a thing.

Now that you have taken it apart, wipe off the worst of it, reassemble the axle and fill with gear oil, and drive it with the hubs locked. This 'sludge' (harmless) will eventually migrate into the gear oil.

@SteveH
Thanks for replying. I was hoping that was the case. Since this is my first rebuild, I wanted to be certain before I undertook anything drastic.
I'll finish wiping off the grease from the diff and then will reassemble.
I am very much in your debt for assuaging my fears. Good to know.
Thanks!
Kerry

 

[Paul_A]

It sounds like you are in danger of over thinking it. Unless you have significant backlash in the ring to pinion or spider gears, I highly doubt that you have an issue. The remaining grey goop will dilute in the new gear oil. If it ain't broke, don't disassemble it. You'll be fine.

 

[kerryjcox]

It sounds like you are in danger of over thinking it. Unless you have significant backlash in the ring to pinion or spider gears, I highly doubt that you have an issue. The remaining grey goop will dilute in the new gear oil. If it ain't broke, don't disassemble it. You'll be fine.

@Paul_A No backlash in the ring to pinion. Everything still feels really tight and secure.
I'll go ahead and clean off the remaining goo and move forward. Thanks much for responding!