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Simple question...maybe.. about my AMC 20 rear diff.

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Simple question...maybe.. about my AMC 20 rear diff.
R

Rexx66

Jeeper
Posts
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Location
Evansville, IN
Vehicle(s)
1979 Jeep CJ-5
Straight 6, 3 speed
I have a leak from the rear diff and planned on removing, cleaning, and putting new gasket sealer on it to stop the leak... however, I have no clue where the fill plug is. There isn't one on the rear diff cover, am I missing something? Where would I refill the oil, and also what oil should I put in it?
 
You'll find the fill hole in the front of the diff on the driverside. I believe its a recessed allen head. Once out swap it for a pipe plug it will be much easier to remove the next time around. 80-90w
 
One issue I have seen with those M20 diff covers is that if they drag across the bottom surface it will tend to peel away and cause a leak. A solution would be to grind away some of that surface that hangs along the bottom of the cover.
 
I have a leak as well. I am taking the opportunity (and spending Christmas cash) to upgrade to a Riddler diff cover. I will be installing it tomorrow. And thanks Posi, I will look for a pipe plug. I am glad that the new diff cover came with replacement bolts that are not star headed devils.
 
gr8dain said:
I have a leak as well. I am taking the opportunity (and spending Christmas cash) to upgrade to a Riddler diff cover. I will be installing it tomorrow. And thanks Posi, I will look for a pipe plug. I am glad that the new diff cover came with replacement bolts that are not star headed devils.
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Heck, I love those torx heads. Some even so much to use it for their user name.:D
 
While rebuilding my 79, I bought some nice aluminum matching diff covers for the front and rear, with a drain plug for the rear. if you haven't removed yours yet, make sure you have a couple good quality torx bits for your rear bolts. I striped 3 that were stubborn, and had to drill them out. We have a great nut and bolt distributor around here, and I replaced mine with 3/4" stainless steel button head bolts. I didn't like the gaskets that came with my covers, so I bought some better ones. I cant wait to get my frame painted, new suspension and axels put in and get it on four tires. By the way, if you don't know yet, the rear diff bolts are 5/16-18.
 
On the cover torx bolts. The trick to removing them is making sure the torx recess is clean by removing all the dirt and grease. I use a pick and small brush. Then keep the torx bit absolutely straight at all times, turn the wrench very slow, and even.
 
Forget that mess, replace with hex heads!

I was never able to get the cover to seal completely. I tried both kinds of gaskets, just RTV, etc. When I just got my gears redone the guy at the shop told me something that blew my mind: He said the only way he has ever gotten an AMC20 to seal is to attach the cover BONE DRY. I couldn't believe it. Sure enough he put the cover on there, metal on metal with new bolts and lock nuts and I haven't seen a hint of a drop yet. I'd give it a shot.
 
I am not sure just when or why they started using those miserable things, on my '86, I try to get rid of as much as I can so I don't have to carry more tools with me. I have noticed the threads on those things are not round but somewhat of a three sided shape. A stainless replacement is not always the best as they might be of a softer grade and can break, stretch, or bend easier. The harder aircraft bolts are usually a fine thread.
 
Just replaced my diff cover today. And it came with new bolts. I only had one stripped torx bolt.

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Same one I have, mine is black though. :chug:
 
Torxhead said:
I am not sure just when or why they started using those miserable things, on my '86, I try to get rid of as much as I can so I don't have to carry more tools with me. I have noticed the threads on those things are not round but somewhat of a three sided shape. A stainless replacement is not always the best as they might be of a softer grade and can break, stretch, or bend easier. The harder aircraft bolts are usually a fine thread.
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The reason for the stainless was looks on the aluminum and no rust. I figured with 12 bolts nice and tight, it should work out ok. If I tighten the bolts enough to break one, that's way too much. :eek:
 
I've had the best luck just using a stock gasket and cleaning the surfaces well. I think I used a little red spray tack on both surfaced last time. I find I get the worst drag type leaks when I use RTV.


Wooly
 
I been running Riddlers for years. I change oils like clock work maybe too soon sometimes, I always wondered about cooling, I mean they have to cool less then the finned ones? do they cool less being so smooth?:chug:
 
Dan77CJ7 said:
I been running Riddlers for years. I change oils like clock work maybe too soon sometimes, I always wondered about cooling, I mean they have to cool less then the finned ones? do they cool less being so smooth?:chug:
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Just from a technique point of view, fins would cool more than smooth since it provides more surface area. The big question is how hot does it get. Enough to warrant fins? Rod
 
if you tow maybe? I tow nothing, only tote so i think im good.:confused:
 
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