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Unread 07-23-2010, 11:34 AM   #1
Dborns
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AMC 20 leaking question

I did a fluid change on my AMC 20 about 3 months ago. I had it sealed up nice and tight and only had a few instances where it would drip a little bit. Yesterday, I noticed a puddle on the pass. side wheel. It was coming from the bottom of the drum, and not from the wheel cylinder so I know its not brake fluid. After looking closer, I noticed the bottom of the diff. had a small drip again, and there is some past leakage right around the vent on the top of the axle. I drove it last night, and the leaks have stopped.
When I got under it today, I found the vent was blocked with dirt and grease. Also, after some research, I found out that I'm supposed to have a hose on it, (the vent), which is missing. When I opened up the fill hole, I had about 1/2 a cup of fluid come out, so I'm assuming I overfilled the diff.
So if its on level ground, should I open it back up and let it drain until it stops? I know the fluid should be at the bottom of the fill hole, so if I let it drain till it stops, it should be at the right spot.
If I'm not going through any deep water, do I need to put a hose on the vent; and if so, is the end capped or left open and placed at the highest point?
I haven't opened the pass. side wheel yet to see if there is brake shoe damage or not; the brakes seemed fine.
Thanks

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Unread 07-23-2010, 01:59 PM   #2
texasimport
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With out letting it vent and if it is overfull at all that oil will find a way out when it expands "gets warm". Why not put the vent hose back on. It would cost you about $2 for the hose and take 5 minutes to plumb it back in.

Yep, make sure the rear end is level, front to back then open the plug and see what comes out.

This could be just the excuse you now need to get rid of the stock two piece axles " if they are still in your 20" and upgrade to Moser 1 pc. Then you can replace those old tired seals and be done goofing with that rear end for a while.
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Unread 07-23-2010, 02:54 PM   #3
Dborns
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I've read alot about getting rid of the 20, and going with one piece axles. I just figured if it isn't broke.... I've seen alot of info on them and how they are so hard to seal and keep from leaking, but since I changed the fluid, I've only had a few instances of just a few drops coming out on an incline for some reason. I don't do any off road stuff, so I'm going to stay with them now and address the one piece issue when I go through the whole Jeep.
Since the diff. fluid found its way past the seals, are they toast? Like I said I haven't had a chance to open the wheel to see what condition the shoes are in, but would the seals be ok with the vent tube opened up now?

As far as the vent tube; is the end just open, or is there a plug? I guess if its supposed to vent, it should be open, but is there a part that goes on the end of the tubing?
Thanks for the info.
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Unread 07-23-2010, 03:26 PM   #4
texasimport
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I am certainly no expert, we have plenty of them on this forum already . . .that said, I think there was some sort of end cap on the hose when the jeep was first built. Mine however has none, it just has a loose fitting screw that allows pressure to vent but not just an open hose.

As for the seals, hard to say. Likely they weren't hurt by a little pressure pushing oil past them but. . .time will tell.
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Unread 07-23-2010, 03:37 PM   #5
Dborns
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Ok, I'll start looking around for some vent tubing and a "plug". Can someone also tell me what size the fill hole plug is on the AMC 20? I've tried square sockets and the socket wrench itself, and can't find anything that fits right. I've had to use a pair of pliers and don't want to do that anymore.
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Unread 07-23-2010, 03:46 PM   #6
82JeepCJ7
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Just go down to your local autoparts store and pick up some 1/4" fuel line, a inline fuel filter, and a couple of hose clamps. Cut off a 12" piece of hose and hang onto it. Run the vent hose from the axle up to somewhere dry (original was ran up between the rear wheel well and the back of the tub). Put the fuel filter on the end of the hose and use the 12" piece you cut off on the other end. Once the hose clamps are tight, take the 12" end and loop it back to the body of the filter and zip tie it in place. Secure it up in the dry spot and forgettaboutit.
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Unread 07-23-2010, 04:29 PM   #7
texasimport
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I like the fuel filter idea, keep dirt out and let her breath. . . .
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Unread 07-23-2010, 08:40 PM   #8
Dborns
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That is a good idea, I'll pick up the parts tomorrow. Any idea on my other question about the fill plug size? Its not real important but I don't want to keep using vise grips and tear the plug up..
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Unread 07-25-2010, 12:09 AM   #9
82JeepCJ7
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Measure the plug and see what size the square is. Pick up some square stock at a hardware store and just use that and a wrench to tighten/loosed the plug.
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Unread 07-25-2010, 12:39 AM   #10
Coiz
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Quote:
Originally Posted by Dborns View Post
As far as the vent tube; is the end just open, or is there a plug?
Here is the stock style vent tube breather.

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Unread 07-25-2010, 01:24 AM   #11
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Fix the vent hose first. If the vent hole is blocked, it will cause a pressure build-up in the differential when it gets warm. That's what the vent is there for -- to equalize the pressure in a hot differential. The end fitting that was shown above is the correct one, and you can get them a lot of places. However, I know a bunch of people that just attach the hose to the diff vent and run the hose up as high as they can get it. Just be aware that if you enter water that is deep enough to cover the open end of the vent hose, then you'll suck water into the diff and you'll have to drain, flush, and refill it. BTW, your front diff and your t-case should also have vent hoses attached to them. I run my vent hoses up to the passenger-side grill brace in the engine compartment. Once you have the new vent hose attacked, blow into the hose and make sure it's clear to the diff.

Don't worry about changing the seals until you have fixed the vent hose and have drained the excess gear lube out of the diff. Yes, do that on level ground, and with a COLD diff.

If, after you've done that, the seals sstill leak, then replace them.

BTW, if you do decide to go to one-opiece axles (such as Superior or Moser), you won't be changing the AMC 20 diff -- you'll just be changing the axle shafts, the outer bearings, and the outer seals.
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Unread 07-25-2010, 06:16 AM   #12
deadeye
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Quote:
Originally Posted by Dborns View Post
Any idea on my other question about the fill plug size? Its not real important but I don't want to keep using vise grips and tear the plug up..
Mine takes a 3/8 allen wrench.
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Unread 07-25-2010, 05:34 PM   #13
Dborns
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I meant to pick up the tubing today, but didn't get a chance. I'll ask for the vent tube breather, and if I can't find it locally, I'll grab a fuel filter. What I don't understand is that I've driven this thing since Jan and haven't had any issues with fluid leaking out the drums. The vent ni**le was packed tight with dirt and grease, so I know it didn't just get plugged, and I hadn't driven it for about 2 weeks, moved it out of the garage, and it started leaking. I know I've got to stop trying to understand why stuff leaks or breaks on my CJ.
Thanks for the input.
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Unread 07-25-2010, 11:30 PM   #14
82JeepCJ7
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Apparently your Jeep was pissed because you had not driven it.
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amc 20 , differential , differential fluid , gear oil , leak

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