Dilemma on rear axle shaft replacement

[BMarino]

Hi everyone.

My truck is a 1994 4WD Pickup Xtra Cab, 22RE manual.

I need help on a dilemma. Here's the issue: when replacing the rear axle shaft bearings, one of the axles was nicked when removing the retainer. The nick is hardly 0.5 mm deep. I don't use my truck for wheeling, but I do use it to haul stuff (heavy stuff sometimes) and on rough offroading, mainly traversing forest service roads and rocky paths and river crossings on the sierras in Mexico.


Here's the nick I'm talking about:






Now, I read everywhere that "any" nick on the axle shaft surface originates a stress riser spot which can eventually cause the axle to fail. So I went on and after months of searching (haven't moved my truck once since then), found a spare rear axle shaft in a junkyard. It is visually without flaw, except for this:




For reasons I can't imagine, it was smashed at those spots. Now, I don't know if this is something which could cause any issues, but it got me thinking if it is really the best idea to replace my original axle shaft with this one. For one, I have no idea on what king of abuse an axle shaft sourced from a junkyard has been subjected to (even if visually it seems flawless). Additionally, and here I'm purely guessing as I'm no engineer, it jumped on my mind that maybe it is important to have axle shafts on both sides of the differential with the same accumulated metal fatigue. If I replace one of them, this would likely no longer be the case.



So the dilemma is:

Is it safer to stick with my original, nicked, axle shaft, obviously if, and only if, the nick on it isn't really that of an issue (?)

OR

Is it safer to eliminate the risk that nick represents, and replace the original shaft with the junkyard rear axle shaft (?)



In short, which is a greater of a risk:

Trusting my nicked axle shaft, or trusting an apparently flawless axle shaft, with an unknown history of possible abuse?




I'll greatly appreciate any help or advice given!

 

[DaveInDenver]

A nick or flaw is acceptable ... until it's not. Toyota axle shafts are fairly oversized for the weight of the truck so I wouldn't be worried about immediate and instant failure the moment you let the clutch out the first time. But when exactly that nick causes a spreading crack is impossible to predict. Just the right twist at just the right moment. It's at an unfortunate spot on a corner but on a thicker section. But I've seen people re-use some pretty abused axles, bearings seized, that sort of thing. If it was on a sealing surface it would be no-go for sure.

Your dilemma is understandable. I'd want to trust any axle that I've owned for many miles and years over one that was obviously abused. But if all the donor axle has visually are those broken tabs and otherwise doesn't appear compromised, yeah, I dunno. Give it a good cleaning and inspection, no nicks or deep scratches, discoloration, pitting or worn spots.

If nothing seems off I'd probably go with the junkyard one then maybe assemble the nicked one as a spare. Carry it when you might be far enough away that a broken axle would be a real problem. Or vice versa, build the junkyard one as a spare. A machinist might be able to repair the nick if it really worries, but I'm not sure I'd personally trust a shaft that was welded and machined over one with a nick like that.

 

[bkg]

i'm confused... is this your original shaft or a junkyard shaft?

if junkyard, just run the original and be done.

personally, I wouldn't worry about this particular shaft... i'd run it.

 

[luthj]

Take a file or dremel grinding head and smooth the nick out. Don't remove any more material than necessary. The shaft is no stronger than its smallest diameter. Which is well under that nick area. The groove next to it for example. You have nothing to worry about. Steels fatigue limit is around 80% of yield. That nick wouldn't make a significant stress riser in that location, and if you are running at 80% of yield strength for the shaft routinely, you have other problems.

If the nick was located in the fillet area near the wheel flange, there would be more cause for concern.

 

[BMarino]

i'm confused... is this your original shaft or a junkyard shaft?

First and second photo are original shaft. Third photo is junkyard shaft.

 

[BMarino]

Take a file or dremel grinding head and smooth the nick out. Don't remove any more material than necessary..

All right. So I'm guessing this (on the OTHER original axle shaft) deserves the same treatment?

If the nick was located in the fillet area near the wheel flange, there would be more cause for concern.

Sorry for my ignorance, but what area is this? Is it somewhere on the axle shaft or are you talking about the wheels/rims?

 

[luthj]

This is the more critical area for damage. That small nick still wouldn't be a problem here though. Any where there is a smooth transition, you don't want to make it sharp. There a similar purpose small fillet at the bottom of the groove, which would be a no-no for significant damage.


The light deformation on your third picture (outer face of wheel mounting flange) is not a problem. Double check for any signs of cracking, but that is a strong area.

Honestly if I saw that nick on a part in service, I would just leave it. If you have it apart already, go ahead and smooth it out. If the nick was more than 2% of the parts overall thickness deep, or had signs of cracking around it, that would be a problem.

 

[DaveInDenver]

All right. So I'm guessing this (on the OTHER original axle shaft) deserves the same treatment?

View attachment 502359

This one looks a little better to me, less deep and not oriented in a way it would particularly encourage cracks. A bit of filing to smooth it but that's typical wear from pressing bearings on and off. The other probably happened when someone was cutting the inner race off.

Sorry for my ignorance, but what area is this? Is it somewhere on the axle shaft or are you talking about the wheels/rims?

He's talking about the narrowed section of shaft at the bottom of the step. Any time a shaft transitions from thinner to thicker the sharpness of the step creates a stress riser. You'll sometimes see a radius machined to relieve it. But the groove there to hold the C-clip has sharp edges from the factory IIRC so Toyota I don't guess is worried about it.

 

[BMarino]

All right then.

I decided it's best to keep using the original axle shaft. Maybe try to smooth out the nick edges, probably leave it as it sits, don't want to make it any worse.

Does anyone know what purpose those tabs at the outer face of the wheel mounting flange have?

 

[DaveInDenver]

Does anyone know what purpose those tabs at the outer face of the wheel mounting flange have?

I don't. I've assumed they were necessary for the casting or machining processes, like a place for a lathe to engage when turning the shaft, or to support the ring from shearing off when you hang a wheel on it. I really dunno.

 

[BMarino]

Thanks everyone for your useful replies!

 

[BMarino]

UPDATE

I just noticed something that more than likely will change my decision:


The original axle shaft has only 1 original (stock) wheel stud left. The other 5 studs are not original as they are in fact shorter in length. This will be a problem for fitting a set of OEM Toyota alloy wheels I sourced from a scrapped 93 4runner, as those 5 studs evidently are too short for securing the lug nuts safely.

The junkyard shaft instead still has all 6 original wheel studs.


At this point I must point out that no more than 1 year has passed since I bought my truck, and hadn't noticed this fact until now that I pulled out those axle shafts. I've put considerable work on it to put it up to shape, as previous owner had somewhat neglected taking proper care of it. Things as no regular oil changes, no thermostat, bad coolant, springs missing inside the manual hubs, shot shocks both up front and back, various shot gaskets, etc. But, 22RE motor running smoothly and flawless frame and very good body condition, and overall a strong appearance underneath the neglect it had to endure, was what got me confident in buying this truck and start spending money and time on it.


Now, I know I could simply switch wheel studs from the junkyard axle to my original axle and be done with it, but I'm thinking: why would 5 out of 6 wheels studs need to be replaced on an axle? In fact, what reasons are there for a wheel stud to need replacement? Other than someone ruining the threads when incorrectly or clumsily fastening the lugs, I can't imagine any other reason than giving a heavy beating to the axle, but then again I don't imagine how could this even ruin a wheel stud.


At this point I'm thus thinking to better use the junkyard axle, as it still having original studs on it adds more reasons to think it hasn't been abused.



What do you guys think?


.

 

[DaveInDenver]

Wheel studs shear mostly from shops using impact wrenches to put cross threaded lug nuts on or way over torquing and stretching them. Or the lug nuts rust on. New wheel studs alone I don't think means a whole lot. The truck is 25 years old, stuff like that is bound to happen eventually. But taken in whole with other clues could add to evidence a truck or axle has been abused. If all 5 replacements were put on at the same time that's more weird. Does the truck have super low transfer case gears or double t-cases? It's hard to develop enough torque from a 22R-E even in low range, 1st gear to do that but with a Marlin drivetrain you could.

 

[BMarino]

No, truck was completely stock. Stock gears, stock transfer case, etc. It even had 25 years-old Bilstein-Toyota shocks still mounted in the back. Truck has over 240 k miles.

 

[luthj]

I had a shop wreck 3 lugs in one go. They put an impact on them and they galled terrible. When I had to remove them to change a flat, 3 of the studs twisted and broke off! Pressing the studs out isn't very hard. Just make sure they fit well when replaced.