Wierd differential in 1984 j10

[marc]

Yet another newbie question. The rear differential is seeping lubricant so I slipped under the truck but could not find an access hole to check the level of lubricant. It does not match the differential shown in the repair manual which has an access plug. I have not been able to find a rubber fill plug or screw plug. The back plate of the differential is held down by some kind of round head torx screws instead of bolts. I welcome any suggestions as to what this differential is. I will attempt to find an alternative filler somewhere on it.

Marc

[rocklaurence]

Its a M20 differential and is a larger version of the AMC20 in CJs and AMC cars. Its as strong as the D44 but IDK where the level plug is--maybe neat the pinion.

[fulsizjeep]

Yes, AMC-20



Lots of good info on this site, save the link.
https://oljeep.com

[RamJetFSJ]

Fill plug is on the casting, drivers side, sorta facing the front of the car. It probably covered the grime.

[Stuka]

The M20 has a fill plug in the housing, on the driver side as I recall about mid way back from the pinion facing forwards.

EDIT: Ahh, answer was already posted.

[marc]

Thanks everyone for your assistance. I found the fill plug, got it out with patience, PB Blaster and an Allen Socket. I was able to verify the level of gear oil. At some point, I will renew the gaskets on the differential covers. A couple of questions, one is the M-20 the same as the AMC20 or at least use the same cover gaskets? Does anyone use anti-seize on the fill plug which I gather can get horribly jammed and risk rounding out the Allen hole? Anyone ever siphon out the gear oil from the differential. I have read about pumping it out of a filler hole but siphoning it out, while slow seems to be a way to set it up and do something else while it takes care of itself?

[RamJetFSJ]

Yes, it’s effectively a AMC-20 (technically the full size jeep designation is the M23). There are some differences from the little jeep M20, but the cover gasket is the same.

[tgreese]

From what I understand, the M23 is the same housing and gears as the M20 used in the CJs. However, it has heavier tubes and the axle hubs are welded to the shafts. This eliminates two of the main objections to the M20, ie bending tubes and hubs spinning on the axles. The M23 should have larger outer bearings than the M20, to support the added weight of larger vehicles. Both of these axles are based on the AMC "Corporate" axle used in their passenger cars, and they are sometimes referred to as such.

[Stuka]

From what I understand, the M23 is the same housing and gears as the M20 used in the CJs. However, it has heavier tubes and the axle hubs are welded to the shafts. This eliminates two of the main objections to the M20, ie bending tubes and hubs spinning on the axles. The M23 should have larger outer bearings than the M20, to support the added weight of larger vehicles. Both of these axles are based on the AMC "Corporate" axle used in their passenger cars, and they are sometimes referred to as such.

The center section is a different casting as I recall to allow for the larger tubes.

The outer bearings are definitely different with the M23's being significantly larger than the M20's. Carrier and pinion bearings are the same.

[carnuck]

M23 was also used in H1 Humvees.

[Stuka]

M23 was also used in H1 Humvees.

Technically not an M20 or M23. Its an independent suspension that uses the same R&P as the M20/23, but that's it. The housing is different, and it uses stub shafts in the carrier that the CV slides over.

And because of the geared hubs, the CV's and R&P don't have much load on them compared to a conventional setup.

[tgreese]

Portal axles: https://en.wikipedia.org/wiki/Portal_axle