Loose key in rear axle
 

Is there any way to repair a worn keyway in the rear axle of a model A? I have a new key but it is loose in the axle keyway.

Re: Loose key in rear axle
 

You could try using a center punch at the sides of the keyway to move metal into the slot. Do this with the key in the keyway. This would be a stop gap repair where the real repair is to replace the axle.

People have said that the key transmits the torque, but the real thing that transmits the torque is the taper on the hub and axle. The nut must be kept tight. I have heard various torques to tighten the nut to but I use a lot more than most. I would contend that 100 foot-pounds is minimum.

Re: Loose key in rear axle
 

My uncle used to say As tight as you can get it and then a quarter turn

Re: Loose key in rear axle
 

i worked on harleys some over the years ahd the torque on the head bolts was....as tight as you can get it plus another half turn

Re: Loose key in rear axle
 

It is possible to have the axle slot "enlarged" and have a "step key" to take the hub.

A fair amount of precision work in this. Possibly better to just get a new axle half.

In buying a replacement, have a key in your pocket and hopefully you'll have a choice of several. Check for a groove at the oil seal (can be a source of failure) Mostly the gear ends look good, but give it a look.

Joe K

Re: Loose key in rear axle
 

How is the keyway in the hub?

Re: Loose key in rear axle
 

Just curious, can the key way be welded up and then recut?

Mike

Re: Loose key in rear axle
 

This is possible - but you're probably talking full weld/magnaflux/lathe/milling machine rebuilder.

You essentially end up recutting the taper on the axle. This to restore (and prove out) the axle taper as "collinear." Possibly to result in "shims" to make up the difference?

I have heard of someone who cut the keyway on the opposite side. Were this mine I would make a "filler piece" to fill in the old shaft key way.

In mounting a hub, the hub actually "stretches" a bit. I.e. a "plastic deformation." This wants to have "support" in the old keyway area lest the wheel rotate "off-center" in plastic deformation.

Joe K

Re: Loose key in rear axle
 

It sounds like Joe K is talking about used axles. Good idea. You can put an ad in the Barn "The Swap Meet" side.

Re: Loose key in rear axle
 

Well, my choice would be "good used" rather than the available "new" where the punkin gear is press/welded/whatever to the shaft - and prone to come apart.

We're now at the point where the wife asks "What on earth am I to do with ALL those Model A parts in the barn after your passing - I'm going to call a scrap yard."

I'm not at all to the same degree but one is reminded of "Page's Model A Garage" in Haverhill, NH. 3 large barns FILLED with Model As, parts, and support ephemera.


Joe K

Re: Loose key in rear axle
 

Some day, darling, all this will be yours.

Re: Loose key in rear axle
 

Has anyone tried Loctite 680?

Re: Loose key in rear axle
 

All of the repair techniques mentioned so far are not structurally sound. If the key gets loose, it will be unable to transmit torque to the wheel. Moreover, the opposite axle key will become more highly loaded shortening its service life. There is no reliable fix for a distorted key-way in the A's axle other than to machine a new one. The axle key must have a snug fit with total contact in the key-way to efficiently transmit the engine's torque to the wheel. I suggest that you replace the axle or have a new key-way cut into your existing axle. The new key-way should be about 180 degrees away from the bad one.

Re: Loose key in rear axle
 

Bob, your slides are a huge help to “visual learners” like me. Many narrative descriptions baffle me, but I understand pictures. Many thanks!

Re: Loose key in rear axle
 

Dave, you might want to refer to a thread started in October 2020 by Bob where tapers were discussed. The keyways and keys wear because the mechanical joint of the engineered locking taper has failed most likely by improper tightening of the axle nut. If you would review that thread you might learn about tapers or Google taper fits. It appears Bob has not come to understand how locking tapers work.

Re: Loose key in rear axle
 

If you don't want to replace the axle, which would be the best, file the radius out of the bottom. Then measure very carefully and make a stepped key that fits tight in the axle. I had to do this to a brand new million dollar shaft at work that the manufacturer screwed up the keyway. We couldn't send the shaft back as the machine was already torn apart and had to be put back in use. It takes time and patience but can be done.

Re: Loose key in rear axle
 

I agree with Richard Knight (Post #15). The taper is there to transmit the torque. It was put there in the very early days of the Model T to replace a straight axle that caused problems. Anyone who has used a lathe and put the tapered tool in the tail stock knows that it transmits torque and is hard to remove without backing off the tail stock to force it out. The key and keyway get damaged when the nut is loose and the key transmits the torque.

Re: Loose key in rear axle
 

Ditto

Re: Loose key in rear axle
 

This is my wheelhouse after rebuilding in excess of 350 Model A and v8 axles over time….. if you have a bad key way on the axle also inspect the hub . The key must fit snug in the axle and the hub . If it is worn and you will most likely see wear on the sides of the axle key, it is best to replace the axles as opposed to undesirable fixes of piening to make it tighter or other methods of band aids.
Loose hub nuts are usually the culprit source of the cause and over time they get worse.
I use to torque the rear axle Nuts to 150, and backed my torque to sometimes 125. If you have good threads it should take it. Use a good new axle nut and make sure that the nuts fit the threads well ( not loose or rocking in the axle - no load).
It is beat to replace the axles if the keway is not sharp . It is easy to tell.
I hear of folks tightening snug with a crescent wrench and low torques. That is NOT recommended and in the best interest of safety….. and always cotter pin. Yes there are stories of Hub/drums coming off… and they are true. How many backing plates have you seen that are flat bottomed before… yea quite a few. Imagine that happening when you are motoring down the road!! You get my drift here.
Folks usually don’t “restore “ the rear axles due to lack of knowledge, tools, and understanding of them and thinking they are turning so they must be ok. Do you treat your engine and trans ok just because they are turning ?
Always inspect all parts… torque the rear axle Nuts to 125 foot lbs. use the thick undamaged axle washers with a well seated out hub seal.
Those if you who’ve been to one of my rear axle seminars at the Marc nationals have seen my axle stub pass around showing broken axle ends !
Inspect and keep ‘em tight!
Happy “A” motoring !
Larry Shepard

Re: Loose key in rear axle
 

Larry, Have you had any luck in shimming axles that are rubbing the backing plates or the inner side of the drum against the emergency brake band?