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Old 10-13-2014, 10:13 AM   #1
Red Mark
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Default Evaluating rear axles

I'm finally replacing a damaged rear axle and could use any advice in evaluating replacement candidate axles.

I've aquired six used axles as candidates for this project. Four of the six are better candidates with good end threads & keyways. All, however have some "grooving" where the grease seal bears on the shaft. Is this going to be an issue?

What else should I consider when evaluating a used axle? Thanks for any input.
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Old 10-13-2014, 10:28 AM   #2
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Default Re: Evaluating rear axles

<All, however have some "grooving" where the grease seal bears on the shaft. Is this going to be an issue?>

Yes it will be an issue. The original style seals were made of rawhide which wore into the steel (Chicago Rawhide was the company, think Chicago had any leftover rawhide haha; it is now CR now that they use modern neoprene and urethane)

There was a thread on this very recently about using Redi-sleeves to restore the diameter, a search should bring it up.

If this is not addressed you will leak gear oil into your brakes

oops '30 coupe beat me by 2 min
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Old 10-13-2014, 10:37 AM   #3
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Default Re: Evaluating rear axles

Dress the worn area with some fine grit emory cloth ( not the plumbers grade). Measure the worst of the worn area with a micrometer. I forget how much wear is acceptable and would have to look for that. Sleeve if necessary as mentioned above. Rod
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Old 10-13-2014, 11:02 AM   #4
Jim Brierley
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Default Re: Evaluating rear axles

the easiest way is to space the seal out a little to move the riding surface to a new spot.
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Old 10-13-2014, 11:58 AM   #5
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Default Re: Evaluating rear axles

Glad I asked. Thanks all for the prompt replies. I'll have to search for the Readi-sleeve thread. I assume there's a right & wrong way to install them.
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Old 10-13-2014, 12:20 PM   #6
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Default Re: Evaluating rear axles

I have always err-ed on the side of safety and replaced them as I have seen first-hand broken axles in the past that took out a fender and caused brake damage.

The question is; how big of a groove does it take to set up a stress riser on that axle? I am told not a very big one. I am not a gambler in this regard however with new axles presently out-of-production, I am taking another hard look. Thoughts??
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Old 10-13-2014, 12:27 PM   #7
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Default Re: Evaluating rear axles

Brent, you are correct as stress is defined as a change in cross sectional area. If an axles wear is within acceptable limits I dress with emory cloth to make the change more gradual which spreads out the stress. This is to not have all of the stress isolated in such a small area.

I do prefer to have the axle in a lathe when dressing the wear area. Sleeves are a last resort when cost is an issue IMHO. Rod
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Last edited by Rowdy; 10-13-2014 at 12:46 PM.
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Old 10-13-2014, 12:33 PM   #8
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Default Re: Evaluating rear axles

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Originally Posted by tbirdtbird View Post
<All, however have some "grooving" where the grease seal bears on the shaft. Is this going to be an issue?>

Yes it will be an issue. The original style seals were made of rawhide which wore into the steel (Chicago Rawhide was the company, think Chicago had any leftover rawhide haha; it is now CR now that they use modern neoprene and urethane)

There was a thread on this very recently about using Redi-sleeves to restore the diameter, a search should bring it up.

If this is not addressed you will leak gear oil into your brakes

oops '30 coupe beat me by 2 min
Yes, Nephew, I remember that them leather pinion seals on the early Mopars would SQUEEL! The factory MUST have installed them DRY! We'd seal the dust slinger to the pinion nub with DUM-DUM & fill it with ATF & after 1/2 hour, or so, it would soak into the leather & the noise was GONE, PERMANENTLY!
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Old 10-13-2014, 01:04 PM   #9
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Default Re: Evaluating rear axles

I grade and evaluate the axles by the critical areas 1st, threads, keyway, taper, gear end, and lastly the seal area. If the seal area on the axle is worn it's really not that big a deal. I would not use an axle just because that is the problem if all other areas ( threads/Keyway,taper,gear) are good. As some have said you can add a spacer before the seal is driven in, use a speedy sleeve, or dress it down. I would not turn down the axle in any way on a lathe to reduce the dimension. In general terms you are not going to leak lube into your brakes..... I've torn down and rebuilt many rear axles (over 150) and really can't say that I've had any one of them oily because of that seal alone.
Pick the best original axle you can taking all the other critical areas into account, key fit, hub fit, threads, gear end.. .and if there's a little wear on it at the seal you can use one of the repairs and also know that with a new neoprene seal it will be OK
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Old 10-13-2014, 01:23 PM   #10
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Default Re: Evaluating rear axles

I do not use any tooling, just emory cloth. I only radius the high edge next to the wear and do my best not to reduce the dia. Yes this can be done easily without being it a lathe, but takes less time in a lathe. My only goal is to spread the stress out over a slightly wider area instead of a concentrated area. Rod
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Old 10-13-2014, 01:31 PM   #11
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Default Re: Evaluating rear axles

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I grade and evaluate the axles by the critical areas 1st, threads, keyway, taper, gear end, and lastly the seal area. If the seal area on the axle is worn it's really not that big a deal. I would not use an axle just because that is the problem if all other areas ( threads/Keyway,taper,gear) are good. As some have said you can add a spacer before the seal is driven in, use a speedy sleeve, or dress it down. I would not turn down the axle in any way on a lathe to reduce the dimension. In general terms you are not going to leak lube into your brakes..... I've torn down and rebuilt many rear axles (over 150) and really can't say that I've had any one of them oily because of that seal alone.
Pick the best original axle you can taking all the other critical areas into account, key fit, hub fit, threads, gear end.. .and if there's a little wear on it at the seal you can use one of the repairs and also know that with a new neoprene seal it will be OK
Larry Shepard


It is my understanding that the seal is a grease seal, not an oil seal. It's purpose is to prevent grease that is pumped in through the grease fitting from traveling down the axle shaft toward the differential.

The design thought is that when grease is pumped in through the grease fitting the seal forces the grease to travel outboard toward the wheel bearing. The large grease seal in the brake drum act as the other end of the trap and forces the grease into the bearing.

This was not one of Henry's better ideas, and a few years after the Model A the grease fitting was discontinued in favor of hand packing the bearing before installation.

I have taken a good many rear axle assemblies apart and found the original CR seal wasted away and with no sign of differential oil in the brakes. In many cases the owner continued to pump grease in through the fitting and the grease then centrifuged around the axle shaft. The more that was pumped in the larger the diameter and the further toward the differential. In many case I found the center section of the axle rusted and devoid of either grease or oil.

If the proper level of oil is maintained in the banjo no oil with reach the seal.

I completely disregard any wear in the axle caused by the seal. The important thing to look for is any cracks at the key slot or damaged threads. The gear end is usually in good shape unless it sat in water and is completely ruined by rust.

Tom Endy
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Old 10-13-2014, 02:17 PM   #12
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Default Re: Evaluating rear axles

Thanks again all for the feedback. As usual, some differing opinions, but as always, food for thought.

Larrys40, this was also my order of priority when seeking out potential replacement axles. Always good to get a second (or third) opinion, though. The wear grooves in question are present, but not excessive on the examples I am considering (enough to catch your fingernail). But, this is enough cause for closer examination.

Glad I checked the prior thread mentioned - "Acceptable rear axle wear". There I found suggested reading for Tom Endy's tech article on differential rebuild. Impressive to say the least. My plan was to just replace the damaged axle & grease seals. That's still the plan. But, if other factors drive a more thorough rebuild, I'm prepared. Thanks, Tom.
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Old 10-13-2014, 02:24 PM   #13
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Default Re: Evaluating rear axles

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Originally Posted by Tom Endy View Post
It is my understanding that the seal is a grease seal, not an oil seal. It's purpose is to prevent grease that is pumped in through the grease fitting from traveling down the axle shaft toward the differential.

The design thought is that when grease is pumped in through the grease fitting the seal forces the grease to travel outboard toward the wheel bearing. The large grease seal in the brake drum act as the other end of the trap and forces the grease into the bearing.

This was not one of Henry's better ideas, and a few years after the Model A the grease fitting was discontinued in favor of hand packing the bearing before installation.

I have taken a good many rear axle assemblies apart and found the original CR seal wasted away and with no sign of differential oil in the brakes. In many cases the owner continued to pump grease in through the fitting and the grease then centrifuged around the axle shaft. The more that was pumped in the larger the diameter and the further toward the differential. In many case I found the center section of the axle rusted and devoid of either grease or oil.

If the proper level of oil is maintained in the banjo no oil with reach the seal.

I completely disregard any wear in the axle caused by the seal. The important thing to look for is any cracks at the key slot or damaged threads. The gear end is usually in good shape unless it sat in water and is completely ruined by rust.

Tom Endy

Tom,
I concur and agree it was not one of Fords great ideas. Hand packing is preferred. I believe the seal was there to help force the grease into the opening between the axle and housing into the hub.... to be captured by the inner seal ( large OD) and just in case any that would come out ( it should never happen) at the outer fiber hub seal under the axle nut washer.
It's just not one I worry about much.... as I said the other issues are much more important and relative.
I concur hand packing a hub bearing is best... Remember the natural shape of the axle housings and drain holes at the carrier end keep the lube where it should be. I've rebuilt a number of Columbias and they have a much higher amount of lube in them into the columbia side housing and I've never had an issue with them either.

Just my own experiences....but as always.. experience is a continuing process! Doing and learning from others...
Larry Shepard
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Old 10-13-2014, 02:25 PM   #14
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Default Re: Evaluating rear axles

I agree with # 10, 11, and 12 postings. I don't worry about a small groove in the axle, but smoothing the top edge over as Rowdy suggests is a good idea. Lube the new seal and slip it over the axle and you will likely find it has a good fit to the axle, and will serve it's pupose well. And, face the seal the right direction as Tom suggests.
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Old 10-13-2014, 07:28 PM   #15
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Default Re: Evaluating rear axles

Only a MAGICIAN could overfill a rear end!
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Old 10-13-2014, 08:29 PM   #16
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Default Re: Evaluating rear axles

One thing I have not heard discussed is that you should have them Magnifluxed. I have seen what appear to be good used axles only to find a crack.

Just my opinion,

Chris
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Old 10-13-2014, 10:06 PM   #17
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Default Re: Evaluating rear axles

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Only a MAGICIAN could overfill a rear end!
Bill W.
It would be difficult to overfill the banjo on a Model A Ford on purpose because it is a fill to spill proposition.

However, there are two ways that banjos become overfilled:

The first is if the special flat washer that is used to attach the U-joint to the transmission main shaft is missing. See photo. This washer acts as a dam for oil that runs under the rear bearing along the shaft flutes. If the washer is missing or has been substituted for an ordinary flat washer the oil will continue on into the U-joint housing. It will continue past the grease seal behind the torque tube roller bearing , which is the same part number as those used in the axle housing. Oil can pass through this seal. If the seal is totally shot more oil will pass. The oil will continue down the torque tube and into the banjo.

The second is if there is a cottage industry modified Borg Warner overdrive installed. Most have a rear oil seal installed that is not an oil seal, but the same part number grease seal used in the axle housings. Oil will seep past these seals and enter the banjo.

If you have a Borg warner installed it is prudent to check the oil level in both the banjo and the overdrive about every 500 miles. If you discover the banjo is manufacturing oil it does not mean you are going to become rich. It means you will eventually starve the overdrive of oil and it will fail, and you will overfill the banjo such that oil will migrate out the axle housings and pass through the grease seals and saturate the brakes.

Tom Endy
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Old 10-13-2014, 10:10 PM   #18
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Default Re: Evaluating rear axles

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Originally Posted by 1930 coupe View Post
Before you install the seals in the housings, slide the seals on the axles to the worn area. If the seal is snug on the axle and there are no sharp burrs, it should be OK. If the seal is loose and you can daylight between the rubber and the axle, you need to fix it.
exactly what i was going to recommend.
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Old 10-13-2014, 10:31 PM   #19
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Default Re: Evaluating rear axles

Quote:
Originally Posted by Tom Endy View Post
It would be difficult to overfill the banjo on a Model A Ford on purpose because it is a fill to spill proposition.

However, there are two ways that banjos become overfilled:

The first is if the special flat washer that is used to attach the U-joint to the transmission main shaft is missing. See photo. This washer acts as a dam for oil that runs under the rear bearing along the shaft flutes. If the washer is missing or has been substituted for an ordinary flat washer the oil will continue on into the U-joint housing. It will continue past the grease seal behind the torque tube roller bearing , which is the same part number as those used in the axle housing. Oil can pass through this seal. If the seal is totally shot more oil will pass. The oil will continue down the torque tube and into the banjo.

The second is if there is a cottage industry modified Borg Warner overdrive installed. Most have a rear oil seal installed that is not an oil seal, but the same part number grease seal used in the axle housings. Oil will seep past these seals and enter the banjo.

If you have a Borg warner installed it is prudent to check the oil level in both the banjo and the overdrive about every 500 miles. If you discover the banjo is manufacturing oil it does not mean you are going to become rich. It means you will eventually starve the overdrive of oil and it will fail, and you will overfill the banjo such that oil will migrate out the axle housings and pass through the grease seals and saturate the brakes.

Tom Endy
Tom,
Strangely enough, Minerva's rearend was GROSSLY overfull, even with the rear jacked up as high as it would go!! I told Gregg, "The trans is probably near DRY"!----Nope, it was perfectly full! We surmised that someone filled the differential while it was UPSIDE DOWN, laying on the floor.
Someone here awhile back, complained about foam coming out the shifter vent. He had filled the trans to the top, before he put on the top tower!
Vermin had been in storage for MANY years, around the block, trans & diff seemed a "little" different sounding than Minerva!! Gregg drained ONLY about 1/8 cup of clean 600W?? from the trans & diff!! Maybe someone died before the Pony Express got there with the oil?? After fill up, both units sound PRIMO!
When buying a car, DON'T ASSUME ANYTHING!!!!!!!!!!!!!!!!!!
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Old 10-14-2014, 01:57 AM   #20
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Default Re: Evaluating rear axles

Quote:
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Only a MAGICIAN could overfill a rear end!
Bill W.
i can.
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