How much will a 35 spline shaft take?

[Stephen]

Any stories, advice, etc?
We should probably specify whether we're talking about a full float or semi float, though it's probably safe to assume most racers will have a full float.


My personal interest is in a GM corp 14 that has a 30 spline 1 9/16" shaft to start with, so it's very similar to a 35 spline 1.5". I know there are 5 and 6 lug hubs out there for other factory type full floaters but the spindles won't clear anything bigger than a 35 spline shaft. So if you can run a factory FF axle it saves buying a housing with new spindles, hubs, etc.
Basically there's a BIG price breaking point between a 35 spline and 40 spline. I do understand there is no difference if you're buying a fabricated housing to start with.

[ntsqd]

Where do the stock 14bff axles break most commonly, in the splines or somewhere along the shaft?

[Stephen]

From the couple of stories I've heard, they break along the length of the shaft because the stock shafts are smaller dia on the shank than the spline minor. But they don't break much in recreational offroad use (which is where my background is) so I don't have much background for desert use.
Is a 1.5" full float shaft up to a 400 hp motor on 35's for racing?

[GOAT1]

I am running a FF dana 60 with 35 spline 4340 shafts, the working diameter of the shafts are necked down to probably 1.400 and are gun drilled to 11/16" ID. I run 37" tires and am probably just under 4000 lbs. I havent had any problems to date with pre running and rock crawling, but I am only running 220 hp and probably 350 ft-lb torque.

What are you bulding? Useage? weight? tire size? horsepower? etc. I think a well designed 300M shaft will hold up well, you just have to inspect them on a regular basis. I would think your biggest problem would be a fatigue failure that could easily be detected before an ultimate failure.

[GOAT1]

From the couple of stories I've heard, they break along the length of the shaft because the stock shafts are smaller dia on the shank than the spline minor. But they don't break much in recreational offroad use (which is where my background is) so I don't have much background for desert use.
Is a 1.5" full float shaft up to a 400 hp motor on 35's for racing?

I would call Sandy Cone on this one. I would be calling him to get shafts and parts made for what ever rear end you go with any way. He has build a lot of shafts over the years, even 14b stuff and has a good idea of what works. A class 1/10 buggy running 935 CV's essentially uses 1.5" ff shafts, they work but they just keep an eye on them.

[FABRICATOR]

A class 1/10 buggy running 935 CV's essentially uses 1.5" ff shafts, they work but they just keep an eye on them.

Most buggies run an open differential. Most trucks run a spool. Big difference.

[Stephen]

It's still a ways out but I'm planning on a class 3 K5 so I'll have several things working in my favor, smaller tires (35's), 4wd (should take lots of stress off the axle in many situations) and probably 400-ish HP. Depending on whose "3" rules it's built too, it could have a leaf spring rear which probably won't hook up like a linked rear too.

It's hard for me to imagine a 14FF not being enough to race a 35" tire when in my normal world I beat one regularly with a nice BBC, lots of gear reduction, 5500lbs and 42's. And, knock on wood, I haven't even broken a factory shaft.

Cone does seem to be the king of all things cool when it comes to axle parts.

[Josh_K]

It’s not enough in a race application. I am sure it will last a race or two but one day you will break it.

Why do you want to reinvent the wheel? Lots of people have had success with Dana 60 converted to 40 and the good old 9".

BTW, I have heard of 7s that have broken 40 spline axels. Nothing is bullet proof.

[Stephen]

Why re-invent the wheel? I realize what "the answer" for a racing rear end is, but if I can manipulate the CHEAP-LIGHT-STRONG equation a little to end up with RELATIVELY CHEAP-SORTA HEAVY-STRONG ENOUGH, there can be enough left over to buy shocks (or any other $3500 item) after the rear is done. I don't like introducing the budget level into racing any more than the next guy but it's real life.
Why bring this up here? 1: I'm hoping for experienced people to put up helpful info 2: maybe some other racers will pick up good info from this and go racing with a factory full float axle instead of waiting forever to build a $6K rear end. And this could help in some classes where you have to run a factory rear axle.

[Josh_K]

I saw your idea after Ramsey drew a picture in the other thread. It sounds like a good idea.

Josh

[KitRacer]

2: maybe some other racers will pick up good info from this and go racing with a factory full float axle instead of waiting forever to build a $6K rear end. And this could help in some classes where you have to run a factory rear axle.

I'm number 2. I'm very interested in what this and your other thread have to say. These axles are big, heavy, ugly, and can be strong. I want to hear everything that you are doing. I like hearing Ramsey's advice, I've prerun with him, he drives hard, if he says something will live/fail, I would take his word for it. How are you going to truss this axle Stephen? They have cast centers right? That means welding is near impossible. I'm curious as to the cost of a 40 spline axle, disc brake conversion, and a Detroit locker.

[Stephen]

I haven't put much thought into the truss yet, since it depends on suspension configuration but I do plan on welding to the casting, it just has to be done right which is a whole different subject.

If you're going to race it, look into a spool, even a detroit has more moving parts than you need to race. For running on the street a detroit would be good.

I think you blow the budget if you go to 40 spline because I think you have to cut the spindles off but what about the D61 in spirit's stock full that was mentioned before? New spindles? Or were the spindles big enough to hog out for the 40 spline shaft? If they're big enough to cut out, you might be able to do the same with a 14 bolt because I think the D61 and 14FF use the same wheel bearings.

[ntsqd]

I don't see welding to the cast center piece as all that big of a deal. It is HIGHLY unlikely that they are cast iron, which makes them cast steel. Clean cast steel welds very nicely. About the only problem I see is that they are a huge heat sink so pre and possibly post heat are called for.

[Stephen]

I'm pretty sure they're gray cast iron, so nickel rods, pre and post heat, etc become important, but that's another post all together. If only they were cast steel, that would make life WAY easier!

[grantdcol]

I don't want to take this off topic, but I've thought many times of cutting out a steel ring (3/8" or 1/2" thick) that would bolt to the cast center section of my 8.8", sandwhiched under the diff cover. Then the truss could be welded along the length of the ring on top or bottom, essentially welding it to the tubes, and bolting it to the centersection. Has this been tried?

Again, sorry to hijack

-Colin