Mismatch diff splines for "ranch" truck, is it a bad idea?

[Lil'John]

Title sort of states it.

Short: Is using two different spline counts in an axle a bad idea for a ranch truck? 32 spline vs 35 spline.

Long:
I've got a full float dana 60 out of a 2000 Ford e350 van. I've narrowed one side by 7". Stock the shafts are 32 spline. My local axle guy doesn't narrow 32 spline. The axle is going to be open for now. As a temp and cheap "bandaid", I am considering just buying a single 35 spline shaft for the narrowed side. I've got a spare 35 spline side gear.

Aside from being redneck as hell, how bad of an idea is it?

 

[total newb]

You cant bone up for 2 shafts?

It wont matter at all unless youre beating on it and you bust the 32. But if you straight bust a 32s axle anyhow you were on the limit anyhow.

 

[Lil'John]

You cant bone up for 2 shafts?

It wont matter at all unless youre beating on it and you bust the 32. But if you straight bust a 32s axle anyhow you were on the limit anyhow.

I won't say can't push the budget... but it is a cheap ass build. I figure the cost of that shaft covers getting 35 spline outers in the front axle ;)

The research I've done on spline count showed "minimal" difference between 32 spline and 35 spline (stock to stock).

 

[ScottRS]

Ghetto as ghetto can be, but as long as you're not pushing the limits of the 32 spline, should work fine. Will suck at some point (maybe) if you have to tear it all the way back apart to upgrade half of it to 35 spline to match the other half. Torsional strength factor is d^4 so a very small difference there turns into a big one quickly. 35 spline (1.5) vs. 37 spline (1.6) is about a 20% strength gain IIRC. I don't know spline specs on 32 spline offhand.

 

[Lil'John]

Ghetto as ghetto can be, but as long as you're not pushing the limits of the 32 spline, should work fine. Will suck at some point (maybe) if you have to tear it all the way back apart to upgrade half of it to 35 spline to match the other half. Torsional strength factor is d^4 so a very small difference there turns into a big one quickly. 35 spline (1.5) vs. 37 spline (1.6) is about a 20% strength gain IIRC. I don't know spline specs on 32 spline offhand.

Thank you for the data.

The rest of the drivetrain does give a chance of destruction: 472 Cady, SM465, and 2.3:1 transfercase with 35s. It is going to be used largely as a driveway snow plow.

I agree it would suck to upgrade the other side... my plan is to eventually locker the rear so it won't be too bad. But with a full float rear, aside from pulling 32 spline shaft, knock the cross pin out, pull spiders, and pull 32 spline spider, it doesn't seem too bad... if we ignore getting covered in gear oil

 

[ScottRS]

The rest of the drivetrain does give a chance of destruction: 472 Cady, SM465, and 2.3:1 transfercase with 35s. It is going to be used largely as a driveway snow plow.

I agree it would suck to upgrade the other side... my plan is to eventually locker the rear so it won't be too bad. But with a full float rear, aside from pulling 32 spline shaft, knock the cross pin out, pull spiders, and pull 32 spline spider, it doesn't seem too bad... if we ignore getting covered in gear oil

If it's one that you can pull the cross pin without pulling the ring gear. Seems like every one I get into that "I'll just pull the cross pin and leave the carrier in place" turns out that it doesn't work that way. I'm assuming you've already checked that you can do that?

The combo you're listing for powertrain should be OK though, I'd think you'll most-likely run out of traction with an open diff before breaking a 32 spline anything.

 

[Lil'John]

If it's one that you can pull the cross pin without pulling the ring gear. Seems like every one I get into that "I'll just pull the cross pin and leave the carrier in place" turns out that it doesn't work that way. I'm assuming you've already checked that you can do that?

The combo you're listing for powertrain should be OK though, I'd think you'll most-likely run out of traction with an open diff before breaking a 32 spline anything.

I haven't physically checked pull the cross pin without pulling ring gear. But the YouTube videos on installing a Spartan locker in a D60 showed it was possible.

I'm sure with enough drinks, I could do something dumb enough to blow out the rear axle.

 

[Phil]

Summit wants $250 for a 31”-33.5” 1541H 35 spline Yukon cut to length.

Dutchman will sell you a single custom shaft for $170 but a pair is only $305.

Moser will only sell a pair, and it’s $385 them in “Custom Alloy” material.

You may as well at least buy both

 

[Lil'John]

Summit wants $250 for a 31”-33.5” 1541H 35 spline Yukon cut to length.

Dutchman will sell you a single custom shaft for $170 but a pair is only $305.

Moser will only sell a pair, and it’s $385 them in “Custom Alloy” material.

You may as well at least buy both

I'm well aware of the price. Already own one set for exactly the same setup... in a different rig. They were in the $400 range for the pair.

Answer so far is nothing inherently wrong with mixed spline axles... just hill billy gheto.

 

[Rangerrod]

Ghetto as ghetto can be, but as long as you're not pushing the limits of the 32 spline, should work fine. Will suck at some point (maybe) if you have to tear it all the way back apart to upgrade half of it to 35 spline to match the other half. Torsional strength factor is d^4 so a very small difference there turns into a big one quickly. 35 spline (1.5) vs. 37 spline (1.6) is about a 20% strength gain IIRC. I don't know spline specs on 32 spline offhand.

Years ago I remember reading an article in a magazine and on Dana 60 stuff it was roughly 10% increase in strength for every spline count. I don’t know if it’s true but based on diameter seems plausible.

 

[ScottRS]

Years ago I remember reading an article in a magazine and on Dana 60 stuff it was roughly 10% increase in strength for every spline count. I don’t know if it’s true but based on diameter seems plausible.

Probably best to think of it as compounding one spline at a time, as it falls apart somewhat if you try to use it to compare 30 to 35 spline (5 spljnes means 50% stronger? No, more like 75%) or 35 to 40 spline (about 85% stronger). But for small changes, that's not a bad rule of thumb to use for quick-swag comparison.