Axle swap side to side?

[Rktpwrd]

I had a thought as I was working on reassembling my 8.5” rearend with a rebuilt factory posi tonight.

I’m about ready to reinstall the axles (they’re in good shape, no need to replace them), and was wondering what the general consensus was about swapping the axles side to side. Right axle as it came out into the left side this time and vice versa.

My thinking is that the RH axle has spent its whole life up to this point driving the car forward and the splines on the drive side will have more wear and stress on them than the backside of the same splines. The LH side axle however, has mostly just been along for the ride so to speak for its lifetime because it was a non-posi until now.

I suppose there is the possibility that I could theoretically weaken and thin out the splines by doing this over the long term, but...???

What are your thoughts? I’m sure any benefits will be negligible, but it’s an interesting thought if nothing else and might give some piece of mind.

 

[Streetbu]

I would leave them where they are. They may have taken a "set" as far as twist goes and reversing the rotation may cause issues. Now take this with a grain of salt, but that's a stretch, given this is a low hp car. Really I wouldn't worry about where they went back in. JMO

 

[69hurstolds]

I had a thought as I was working on reassembling my 8.5” rearend with a rebuilt factory posi tonight.

I’m about ready to reinstall the axles (they’re in good shape, no need to replace them), and was wondering what the general consensus was about swapping the axles side to side. Right axle as it came out into the left side this time and vice versa.

My thinking is that the RH axle has spent its whole life up to this point driving the car forward and the splines on the drive side will have more wear and stress on them than the backside of the same splines. The LH side axle however, has mostly just been along for the ride so to speak for its lifetime because it was a non-posi until now.

I suppose there is the possibility that I could theoretically weaken and thin out the splines by doing this over the long term, but...???

What are your thoughts? I’m sure any benefits will be negligible, but it’s an interesting thought if nothing else and might give some piece of mind.

If the splines look good and straight in general, and you're not sticking 500 HP to the rear end, you're probably going to be just fine with swapping sides, or even not. Moser can sell you some more if needed.

It's a trick that has been used for the carrier side gears when rebuilding posi units with the same idea. And they're the things that actually have the axle mating splines anyway. So it would be akin to swapping axles. Even as puny as those axles are, with that powerhouse SBC of yours, I think you'll be fine no matter which side went in which axle tube. Recall it's an 8.5. Fairly sturdy. Of course, had you been building for more power, you'd likely be going with 30 splines anyway, so there's that.

 

[bracketchev1221]

I would keep the axles on the same side based on metallurgical set.

 

[69hurstolds]

I would keep the axles on the same side based on metallurgical set.

It shouldn’t matter at this point. He put a posi unit in which changes the spline contact areas anyway so I really don’t see a big deal which axle goes where with a “new” carrier.

 

[bracketchev1221]

It shouldn’t matter at this point. He put a posi unit in which changes the spline contact areas anyway so I really don’t see a big deal which axle goes where with a “new” carrier.

The axle has a twist from the spline to the flange however slight. The metal has been compressed this way for years. The posi doesn’t affect that.

 

[81cutlass]

I'd flip them and not give a second thought.

There was a guy on Turbo Buick that ran into the 9's on stock 28 spline 8.5 axles. He said he would change them every season as over the season they would twist. I can't find the thread but it's in my brain. They had visible twist to them.

Unless the car that you got the rear out of has been on slicks or radials on a track with sub 11's power or been in a wicked crash, the axles haven't yielded (twisted). Stock axles are designed to stay well within the elastic zone of the material properties.

The only risk of flipping them side for side if they DID twist previously is that you have already moved into the plastic deformation zone as the yield strength has been exceeded but not the ultimate strength yet. You could be loading the material in an opposite way but the steel doesn't care. They are induction hardened and it's going to have the same material strength either way.

All of the twist is going to be in the 3/4" between the end of the mating spline with the diff and the start of the axle anyways as that is the weakest part. If they are twisted get new axles. If they aren't twisted it's fine.

Any surface finish change in the dif to spline contact surface from the load vs coast side of the spline is likely just burnishing and surface finish effects only.

 

[69hurstolds]

I see both sides of the equation on this, but assumptions would have to be made in this case because we don't know the specific wear on these particular axles.

Flipping the side gears was mainly for pinion load/coast lash considerations in there would be a so-called fresher surface acting as the load side of the side gear as compared to a worn one from before. I could see it if you had some uneven pinion wear or something, but for a stock rear end with 200 HP or so pushing it on street tires, there would have to be some real crazy sh*t to happen to twist the axles or pinion gears where they were unusable. JMO. I give GM more credit than that. As long as you were within lash specs, send it. Maybe the idea was sorta like rotating the tires to get even wear all around.

You could paint a straight stripe on the axles and come back and check them several years from now and see if the paint line is still straight.

I personally wouldn't hesitate to flip them if desired, but do what you want. It's your car, your axles.

 

[Rktpwrd]

Thanks for the input so far guys, this sort of discussion and points of view is exactly what I was looking for.

The axles are as I said, in good condition with no signs of any twisting. The one thing that I did note however that caused me to start this thread, is that the drive side of the splines on the RH axle are shiny and have a bit of a sharp edge to them, indicative of wear obviously. This sharp edge is what got me to wondering if I’d be thinning them out further by flipping them and potentially causing a bad situation.

So far it’s looking like I should probably stick with reinstalling them back the way they came out to be on the safe side.

 

[64nailhead]

As mentioned, I don’t believe you’re going to have an issue no matter where they line up. But......trying to increase longevity by swapping them side to side ..... no.

The chances of you having an issue with an axle spline is very slim.

I’d like to recommend a way for me to spend your money (because I know we all like that), new set of Mosers - less than $300 here in the sunny lower 48