Installing Aftermarket One Piece AMC 20 Axle Shafts

[Greg]

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I bought One Piece Axles from Tens Manufacturing for my 1981 CJ5.  The bearing sits .09 outside the axle end.  The bearing spacer does not bottom out on the inside axle seal, the lip on the bearing spacer is actually stopping it at the bored lip inside the axle tube.  I called Tens and they said to lathe down the lip of the bearing so that the bearing would sit within the .02 to .06 endplay stickout.  I have two options that I see at this point ... 

1) lathe down the lip on the spacer to get the bearing to seat properly, however, I feel that will affect the strength of the bearing spacer to hold the inner race and bearing in place...

2) stack up some .01 axle shims to get the desired endplay stickout, which would then require at 4 shims to get me into spec...

Any suggestions?  recommendations?  has anyone else run into this issue??

[Moses Ludel]

Greg...Your first photo did not open up.  (I tried to open it, the file extension is not recognized.)  Perhaps you can reload it.

Questions and observations:  First off, if the spacer bottoms against the "step" (arrow in your lower photo) in the bore, and you have too much bearing cup stick-out, the spacer is not going in far enough.  Is TEN suggesting that you machine/lathe 0.030" off the bottom edge of the spacer lip?  This would not reduce the diameter of the lip...When fitted properly, does TEN say that the spacer is not supposed to contact the inner axle seal?  (That would make sense.)  How much gap is there between the inner end of the spacer and the inner axle shaft seal?  It does look like the lathe cut on the lip is not square at the bottom end.  

I searched for TEN's instructions online.  (They can be found at:  http://www.mdwparts.com/install/tenfactory/amc20.pdf.)  This is the key step in the TEN instructions:

"2. Install bearing spacer into axle housing end. (Reference Fig. B) Be sure spacer fully seats in housing. WITHOUT the axle shaft installed, test fit bearing into housing end. Be sure bearing is installed as in Figure A with the inner race facing towards the center of differential. Make sure bearing is against bearing spacer. Bearing should protrude .020” to .060” beyond housing end. (Reference Fig. B) If more than .060 extends beyond housing, remove bearing spacer, then evenly grind bearing spacer OR use original shims to “lengthen” housing end until these measurements are achieved."

You share that the spacer is not bottoming against the seal.  The spacer is also not moving far enough into the bore.  If the spacer does not move far enough into the bore, according to the instructions, the spacer either needs to be machined or ground squarely to allow the spacer to move further into the bore—at least 0.030" more than it does now, enough to achieve the 0.020" to 0.060" bearing cup protrusion.  The option to machining or grinding the spacer is to use factory shims to move the brake backing plate outward from the axle housing flange 0.030" or more to compensate for your 0.090" bearing cup stick-out.  Does TEN expect consumers to machine/lathe the spacer lip?  Was that the conversation?  There would be nothing wrong with using shims to move the backing plate outward, as long as the shim count/thickness is not excessive.  AMC used shims.

Note:  TEN is asking that you install the bearing (not on the axle shaft yet) with the cone's inner race facing the differential.  This means that the taper of the bearing is toward the outside like the OEM.  The illustration in TEN's instructions shows the spacer being much smaller diameter than the housing bore.  That would be incorrect based on the piece you're holding.  The piece you're holding (the spacer) looks close to the axle housing's bore diameter or the bearing cup's O.D. size.  That would make more sense than the instruction's illustration.

The instructions do not talk about axle shaft end play like the AMC "factory" adjustment.  Instead, TEN wants to preload each bearing with the 0.020" to 0.060" bearing cup protrusion.  If the bearing cup butts against the brake backing plate as customary, the 0.020"-0.060" cup protrusion will create a preload on the bearing.  There will not be end play.  The brake backing plate will force the bearing cup against the spacer.  The spacer, if stopped within the axle housing bore, cannot move further inward.  As a result, the bearing gets squeezed or preloaded.  How much?  In step #7, TEN tells installers to make sure the axle shaft still rotates without binding after the backing plate fasteners are torqued.  If binding, there would be a need for more spacer grinding or lathe cutting (both the spacer lip and also the inner end of the spacer, if necessary, to make sure the spacer still clears the axle shaft seal)—or additional shimming between the brake backing plate and axle flange.  Again, you would not reduce the lip diameter but rather shorten the lip's width, cutting from where you have your arrow pointed.  Yes, you would need an adequate shoulder width here.

By TEN design, each side of the axle is set up this way.  (There is no end play at the driver's side axle shaft like with the factory AMC/Jeep adjustment method.)  The TEN kit's spacers act as inner stops for the bearing cups.  The TEN axle shaft bearings are preloaded individually at each side of the axle.  Apparently, the differential spacer block is not in play, which likely means that the axle shafts are slightly shorter at the splined end than the factory axle shafts.  If that is the case, the axle shaft depths/lengths work independently of each other, and the shafts do not contact the differential spacer block.  You would be adjusting each axle side individually with the spacer being ground, lathe/machined or by creating space with the brake backing plate shimming method.

With the TEN conversion, the brake backing plate loads the bearing cup.  With the bearing cup protruding the 0.020" to 0.060" from the end of the axle housing bore, the brake backing plate will flex at its center when the support bolts and nuts are torqued to specification.  That's the TEN design.  Moser does this as well.

I would like to know how much clearance/gap exists between the spacer and the face of the (seated) inner axle shaft seal.  Use feeler gauges to measure this gap with the spacer's lip resting against the axle housing's bore step.   If you do reduce the spacer lip width, make sure that the inner end of the spacer still clears the seal.  I doubt that TEN wants the spacer's inner end to butt up against the seal.  Confirm this with TEN if necessary.

Moses

 

[Greg]

Thank you Moses for the detailed explanation and advice.  I was using the terminology of "end play" in stead of bearing stickout to create preload, that was one of my mistakes...  I did however clean out the axle tube end a little more and also found one of the original axle shims from the AMC 20 axle was a .030 shim.. so I was able to use that shim on the Passenger Side to get the proper bearing load.  The Driver's Side didn't actually need a shim, it ended up being .040 bearing stickout.  I was able to install the axles on Wednesday night. 

To answer one of your questions about Ten's expecting their customers to machine/lathe the spacer lip, my answer is "yes".. that is what they instructed me to do.  I was not comfortable doing that because I thought it would take away from the integrity of the spacer lip strength for holding the bearing in place for not only pre-load, but also when cornering at road speed.  I am glad that the original shim I pulled off the axle from the two piece axle setup just happened to be what I needed!  Phew!!  No need to stack shims.

Ultimately, I was able to get both the left and right sides axles at .040 bearing stickout and the preload seems to be fine.  

I greatly appreciate the advice and help you offered!  It's incredible being part of this group and these forums!  Keep doing what your doing.. we all appreciate it!

 

 

[Moses Ludel]

You're welcome, Greg...I could tell you were trying to do the right thing.  Your concern about lip integrity made sense. 

The differential spacer block is no longer an active member here (no end play side-to-side like the OEM setup).  Your use of a shim at the passenger side would be consistent with TEN's design.  0.040" is smack in the middle of the TEN recommendation, you did really well at the passenger side.  The driver's side is also within their specification. Final test is no binding during axle shaft rotation.

Interesting how the TEN or Moser settings are preload while the OEM is an end play adjustment.  Your 1981 CJ's full-floating front wheel bearings also have an end play specification.  Tapered roller bearings will work under either condition, depending on engineering application, load and operating environment.  A concern with preloaded bearings is heat.  Modern grease helps offset this.  I'm sure that you packed the new axle shaft bearings with an ample amount of quality grease.

Moses

[Awizard4x4]

Hello

I am installing the G2 1 piece axle on an AMC20 in a 1978 CJ5. The instructions show the Outer Seal outside of the Protective Guard. This seems backwards. Mine was assembled like the Ten instructions show. Seems impossible to go together the way the G2 instructions show.
Also, am I right that the backing plate will now preload the axle bearing due to the bearing now sticking out .02"-.06"?

https://photos.google.com/u/0/photo/AF1QipPIATpY7KeeSEMcxtFsdcJ29IGTwMLj8KaJv1o1

https://photos.google.com/u/0/photo/AF1QipODKLrUei2VYgsYTdkBfKtgf62A2D1z-Zb40jur

Thanks

[Moses Ludel]

Awizard4x4...Couldn't view the google photos, but I get the gist of your concern.  Yes, in this approach, the bearing cup stick-out determines the amount of preload on the bearing.  And yes, the backing plate becomes a flexing, preload mechanism with this design. 

These manufacturers have apparently determined that if the backing plate flexes 0.020" to 0.060", the bearings will be preload properly.  The amount of backing plate tension determines the amount of preload on the bearing...This is not the OEM method, which calls for axle shaft endplay. 

To your question, the outer seal/plate cannot be fitted outboard of the dust cover, the bolts would need to be longer, the plate would be unstable, and the dust cover would not withstand the axle shaft lateral/axial pressure.  Hardware would likely loosen, and the dust cover would likely collapse.  As you have discovered, the dust shield is just stamped "tin" and not as stout as the seal plate.

Below is a stock layout for the AMC 20/CJ axle shaft, seal and dust cover.  Note that the shim(s) have a center bore that will slide over the bearing cup.  The backing plate would normally fit between #5 and #6 parts.  The shim(s) #5 would space the backing plate outward from the axle flange to allow the bearing cup to move outward as well.  In this case, the cup's stick-out from the axle flange establishes an end play at the tapered bearing.  The shim(s) set the bearing and axle shaft end play or lateral/axial float.  The backing plate acts as a stop for the bearing cup, but the brake backing plate does not flex and tension the cup.

With your one piece axle shaft design, if like the TEN approach, there is no bearing end play.  (See the link I provided Greg to the TEN PDF instructions with a diagram.) Instead, the bearing cups are preloaded against the bearing cones.  These manufacturers use the brake backing plate as a flexing "tensioner" to press the bearing cups inward. 

The amount of backing plate flex determines the amount of preload pressure.  In the TEN approach, they have determined that 0.020"-0.060" is the amount of preload (backing plate flex/tension) that they want for these tapered roller bearings.  This is a different approach altogether from OEM axle shaft bearings with factory end play:

I trust this helps clarify...Let us know.

Moses