Reconditioned stub axles?
 

Does anyone know if it is possible to have the rear stub axles reconditioned? I was wondering if metal could be put back on the areas that get peened by the wheel bearings and then have it machined down by a local engineering shop?

If so ... anyone know the dia. spec?

I had the inner races collapse (both sides) and bought some second hand items plus new bearings - false economy as I'm back where I started two months or so back.

This is SoCal's fault, of course. He asked me a few days back how the car was running. I said fine. Now this has happened. BUTTOCKS!!!

By the way one single Porsche axle here costs £326 inc taxes. That's $602 in your money. I need two so if it's possible reconditioning is well worth the candle.

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Possibly by welding but I think it would distort the axle itself.

Maybe by plasma arc. Have to find a shop that rebuilds cranks. They would have the proper equipment including the ability to grind the OD to stock. Keep us posted if you find any useful info.

I spoke to our local cam grinder about this when we needed a 924S stub axle (which are $530 new). There's no problem doing it. You may want to have it crack-tested after repairs, but it should be way cheaper than a new one.

There's an excellent machine shop (crank / cam / etc) near me so I'll definitely look into the possibility and post back. So that just leaves me with finding out the diameter of the original spec. Anyone know what this should be?

As the finished surface is NOT a running bearing surface QC could be less than that of a crank journal.

I would make darn sure that the splines are in good shape and not hammered by a loose hub.

Splines are in great shape. And now I have four shafts to practice on - so there's that.

Okay - so I still need the diameter for the area the bearing inner races sit on.

If I put a micrometer on the last of the splined section just before the worn bearing area will this give me the correct diameter for the shop to machine down to?

The surface just inboard of the worn are should be the correct diameter.

I have a couple of used ones. I'll see if I can throw some dial calipers at them.

Cheers mate - that'd be much appreciated - I just found out my micrometer isn't quite large enough to do the job.

Measurements:

On the good part of the stub axle: 1.180" / 1.181" O.D.

Same as the inner bearing race surface.

Undersize/worn part was 1.174

Would think it should be about .0010 to .0015 under the bearing inner race I.D. A slip fit.

Any one have a bearing to measure?

Cheers SoCal, you're a star!

I'll pop into the machine shop tomorrow and see whether they can do the job.

Oh! Golly Geeeee...

Take a good outer roller bearing inner race with you. Tell them it has to be a slip fit. A snug slip fit.

Okay. Took the shafts into a specialist today and this is what he had to say.

Welding is out - the guy behind the counter said that as the shafts are hardened welding them would take out the strength and they may become a liability.

A process known as metal spraying could be employed. Molten metal is fired at the shaft, adheres to it and then is machined down to spec. Possible but, apparently, can be prone to peeling off.

Hard chroming could be employed. I've some experience with the process - I've had the stanchions on my motorcyle re-chromed when they became pitted and started eating up the seals in the front forks. This is the best option but it would require sending the shafts off to be done. Hard chromed and ground down = £160 EACH !!!

That's wayyyyy too much. Not only should I be considering shipping in shafts from Pelican when it gets to that kind of money but also it was wayyyy more than it'd cost to have a pair of forks on a bike done £100 or thereabouts for the pair. £320 to have the bearing areas (not the whole thing) is an insane price.

His last option was to try using Loctite 641 bearing retainer. He reckons the wear on the outside area was so slight that it would generally be considered within tolerance for a raced bearing. The retaining fluid ought to pack out the slight wear in his opinion.

So ... I'm back to square one at the moment. I'm looking around at locating more specialized engineering shops. I figure £100 tops is viable before looking out second hand shafts again (because they seem to be coming off motors with my kind of mileage on anyway).

Any thoughts on the Loctite retainer? It ought to take out the slap caused by the worn area which is cracking the race but is it up to the job of handling the long term stress load?

I've not used a retainer before so I'm slightly sceptical.

From experience, I'd say that the bearing retainer would not work in this application. Check with another machine shop. Unless the bearing is a tight slip fit on the shaft you will have excessive rear wheel bearing play.
Our local cam grinder was going to treat the shafts exactly as they would a worn cam lobe. As I said previously, you should definitetly have the shafts crack tested after repairs. I don't know, but the machine shop should, if after repairs the parts can be stress-relieved. If that fails you need to buy new parts.

The other option is to replace the entire rear assembly with one of a later 944 with the aluminum trailing arms. the bearings in these arms rarely fail. Check around for prices, it's a total bolt on job. You need the whole assembly, including the cross tube, from a '85/2 - '86 model year 944. The '87 and up use a different wheel offset.

I'm going to investigate a few motorsport machine shops (Oxfordshire is the home of Formula one and rally racing so we have a fair few of them in the area). When I built my kit car a stub axle brand new only cost me £25. Wouldn't be at all surprised if it was made in the same factory. I can't believe they're so damn pricey.

So here's the offending shaft. Who would have thought it was so difficult to get hold of a specialist to stick a bit of metal on it and then grind it off again.

I'm still waiting on a few machine shops to get back to me. I've also contacted a couple of prop shaft specialists (one of which built me quite a bit of stuff for my kit car). Hopefully I'll get a result.

Surprised was I when I had a good look through a number of motorcycle mags and found that there were no specialist cam peeps advertising in them at all. In my youth no self-respecting biker had his bike on the road over a Saturday - the engine would be strewn across the drive way whilst he fitted the latest hot cam, Boysen Reed valve, Yoshi head and piston set or whatever.

These days it's all matching dayglo leathers and girly pink helmets with billions of fake sponsor decals all over them.

Even BSH and Street Fighter are filled with leather waist coats and metal jewellry. What's the hell's wrong with bikers today?

When I were a lad a quarter of the ads in those mags would have been engineering shops that could do the job I currently need. Don't even mention the car mags - they'll all fat tires, neon under-lighting and go faster stripes. Bugger.



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