AMC 20 axle seals

[lgbent]

Hi guys & gals, I'm putting 1 piece axles in my 85 CJ & I wanted to know should I put new inner seals in & use grease on the bearings, or leave the seals out and let the rearend oil grease them? Thanks, Grant

[Jim_Lou]

Welcome to the board! That's an interesting question. IMO it's a tossup, but I'd come down on the side of seals and grease. My reasoning is that the engineers who designed that unit probably know more about it than we do, and wouldn't have gone to the expense of machining the housing and buying and installing a seal if they thought that the differential lube would do a sufficient job.

And you can do the mod of installing a grease fitting in the housing and make it even better.

[TeamRush]

Actually, depends on the bearings the one piece axles came with.

If they are Timken set 9 bearings, you need lubricant and outside seal.
(Same bearings used in the Dana 35 axles)

Timken set 9 bearings are TAPERED ROLLER BEARINGS,
NOT BALL BEARINGS,
And they are NOT sealed, so they require lubricant of some kind.

If you want to use axle lube in them,
Leave the inside seal out and drill some holes in the bearing spacers so the lubricant from the differential can reach the bearings,
Then run a good outside bearing to keep the lubricant from escaping the axle/bearings.

OR,

You can use both inner and outer seals and use a high quality wheel bearing grease between the seals to lubricate the Timken Bearings.

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If your axles came with 'Green' brand BALL ROLLER BEARINGS,
They are sealed and won't benefit from any external lubricant even if you do put some to them.

The Green brand sealed bearings require NO external lubrication,
So you use an INNER SEAL ONLY.

Leave the outer seal out of the assembly for two reasons...
1. The seal will burn up with no lubrication,
2. Then it will simply trap moisture, grit, ect. against the bearing and in the axle bearing seats.

Most of the Green brand bearings recommend you leave the outer seal out of the mix, use a bearing retainer plate between bearing and brake backing plate.

Without outer seal, the crap you collect will be able to drain out of the axle end and away from the sealed bearing.

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There ARE variations,
So if you aren't sure, call the manufacturer to find out what they recommend...

These bearings ARE NOT interchangeable on any brand of axles,
The axles require different machining to switch bearings...

And the Green brand ROUND BALL bearings are the lighter duty of the two.
Round Roller (Ball) bearings don't side load very well and are structurally weaker than the tapered roller bearings.
But they require EXTERNAL lubrication and are NOT sealed.
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Superior and Mosier axles are made in the USA,
And use BOTH types of bearings, (upon customer request)
And are both excellent axle companies.

Alloy USA Axles are made in India now and like to break with little or no provocation, I've seen two brand new broken axles this summer alone...
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Now, for PERSONAL PREFERENCE.... (so keep the flames to yourselves)

I prefer the Timken Set 9 bearings when I'm doing one piece axles.
They require a spacer behind the seal, a specifically machined retaining collar, but they support so much more load off camber than the Green brand bearings do it's not funny!

I also prefer TWO seals and using grease instead of just an outside seal and using gear lube...

With both seals in place, and a grease zerk installed on the axle,
You can fill the bearing cavity up with grease, and make it practically impervious to water getting into your gear lube.

It's MUCH easier (and CHEAPER!) to repack bearings once a year than to clean, tune up your rear differential, and replace 1.5 Gallons of EXPENSIVE synthetic gear lube!

Where grease is, MOISTURE CAN'T BE!
If you do it correctly, you have a 3" grease 'Dam' between water and your gear lube that is easy to service/change with a little work to the housing.

Also, you have to keep in mind, that if the differential lube gets low and you are driving on flat ground for a while, you CAN burn up the wheel bearings since they won't be getting any lube!

I don't know about you all, but I HAVE found my diff lube low before!

So I prefer TAPERED ROLLER BEARINGS & HIGH QUALITY WHEEL BEARING GREASE when I'm doing axle replacements.
It's worth the extra seal and time to drill the housing for grease zerk and grease relief plug!

One last bit of advice,
Timken Bearings,
Spicer U-Joints,
Moog Suspension Components,
ACCEPT NO SUBSTITUTES! Anything else is a waste of time and money.