Axle and spline count recommendation for a drag car?

[cjshaker]

I'm needing some input on axle spline count and what type to use in a 90% drag duty car, so I'm hoping I can get some feedback from the regular racers here.

I currently have a heavy duty Currie rear housing with big bearing ends, a Strange Pro Series iron center section with a Daytona pinion support, Detroit Locker and 31 spline Currie axles. I think the axles are the weak point but wonder if anyone has raced with Currie axles and if any problems were had with them? Do you guys think they could withstand a 500hp engine with 5000 rpm launches in a 3500lb car with a stick shift and sticky tires? On the street I don't worry about them because of obvious traction limitations, but I'll be doing some strip time next year.

I've been looking at the Mark Williams and Strange Eng. websights, but they are a little vague about what each axle can handle. So in a nutshell, should I upgrade my axles? And if so, is 31 spline good enough for the above mentioned scenario? And while I'm at it, what if the scenario involved the same parameters but with a 650hp engine? Any input would be appreciated.

[ScotiaFE]

I do it.
I let it go at 5000 rpm and then worry about all the other things that could break.
I'd bet you break the TL before you break an axle.

[jayb]

When I got Mark Williams axles for my Mach 1 in 2005 they suggested their Masterline 31 spline axles.  Said they were good to low 10 second times in a car like mine, which was 3600 pounds and 700 HP.  Probably their premium 31 spline axles would be good for high nines in the same car.

For my Galaxie, which weighed 3935 with me in it, and ran mid 9s, they suggested stepping up to a 35 spline axle.  And I went with 40 spline on my Shelby clone, which was probably overkill, but better safe than sorry.

Hope that helps - Jay

[cjshaker]

I do it.
I let it go at 5000 rpm and then worry about all the other things that could break.
I'd bet you break the TL before you break an axle.

That's right, Howie, you have Currie axles don't you? How long have you had them in the car?
But the difference between the TL or the rear axle breaking being the TL likely wouldn't send me into a wall   I'll be adding a Jerico and Gear Vendors to the equation in the future, and I just rebuilt the TL with an aftermarket large input shaft, new gears etc. So hopefully it will get me through at least 1-2 years before things get a bit more serious.

When I got Mark Williams axles for my Mach 1 in 2005 they suggested their Masterline 31 spline axles.  Said they were good to low 10 second times in a car like mine, which was 3600 pounds and 700 HP.  Probably their premium 31 spline axles would be good for high nines in the same car.

Thanks, Jay. Since the weight and HP will increase, along with the shock of a manual shift car, I was leaning towards the 35 spline, but maybe that's a bit of overkill. MW has a very good reputation. What size studs do you use in the Mach and Galaxie?

[bobb428]

I would go 35 and their is no other choice but M/W!

[ScotiaFE]

The axles are about 10 years old.
I've changed the studs though.
I only use a 9 inch tire also so not a lot of rubber either.
And the clutch is pretty light. so it leaves pretty soft.
Which for me is a good thing. Cause if I start spitting parts out I don't really have
the wallet to fix it.
The clutch will be the key.
I'd rather punish the clutch, than the gear box or rear end.

[afret]

I went with the 35 spline street/strip axles with 5/8" studs for the street Mustang.  Most likely overkill but won't have to worry about axles.  If you already have the setup for 31 spline axles and want to go to 35 spline, you'll have to get the right differential for it and a 3.25" bore case.  If you drive on the street the race axles aren't really recommended for street use. 

[cjshaker]

The clutch will be the key.
I'd rather punish the clutch, than the gear box or rear end.

The clutch is probably more accurately the weak point. Right now it's just a heavy duty Ram unit, not exactly ideal for slicks. A sintered iron unit will wait until the Jerico gets involved.

If you already have the setup for 31 spline axles and want to go to 35 spline, you'll have to get the right differential for it and a 3.25" bore case.

Thanks, Afret. I have an extra 31 and 35 spline locker now. The 31 I just bought to set up with a higher gear set for on the strip. That's partially why I was asking....use the axles I have or cough up the dough for another set for the 35 spline unit? But I also have my doubts on the Currie axles, as far as holding up to years of strip abuse. For just a year or two I'm not so concerned, but if I have to build the center section now, I may as well do the job right the first time so I don't have to change everything in a couple years.

Edit because I wanted to add that MW says on their websight that you can use their 35 spline axles in a large bearing housing, which I have.

[jayb]

On the Galaxie and the Mach 1 I still use the 1/2" wheel studs, but they are the 3" racing units.  I've never had a bending problem, but I always torque the lug nuts.  I think the guys who have issues bending the wheel studs don't have the lug nuts tight enough, and therefore don't have a good clamp between the wheel and the axle flange.

I do have the 5/8" studs on my Shelby clone.  I like them because they look cool 

[ScotiaFE]

Don't get me wrong if I could afford it, I'd have all the good stuff.
I feel lucky I can afford to even get the car down the track in one piece.
If you can afford it go for it.
I will say the clutch is like the shock absorber. The harder the clutch the more shock.
Speaking of that.
Don't over look the rear shocks. If you get into wheel hop territory that will break things faster than any thing.
My Fairlane is a pretty heavy car with me in it so it will never really be a fast car
and I don't take it to serious, kind of like golf.
I can play but I don't really take it to serious. I don't even keep score anymore.

[fekbmax]

I ran moser 33 spline for several years and never had a prob. That was with 1/2" studs and a 4-1/2" bolt circle even. At the time I was running a rollerised C6 with a low gear set and a 5200rpm 9" converter.     Ofcourse  when I changed to the Clutchless shift jerico I went with moser 35 spline/spool setup.. They have one of the best replacement guarantee's in the business...

[afret]

The clutch will be the key.
I'd rather punish the clutch, than the gear box or rear end.

The clutch is probably more accurately the weak point. Right now it's just a heavy duty Ram unit, not exactly ideal for slicks. A sintered iron unit will wait until the Jerico gets involved.

If you already have the setup for 31 spline axles and want to go to 35 spline, you'll have to get the right differential for it and a 3.25" bore case.

Thanks, Afret. I have an extra 31 and 35 spline locker now. The 31 I just bought to set up with a higher gear set for on the strip. That's partially why I was asking....use the axles I have or cough up the dough for another set for the 35 spline unit? But I also have my doubts on the Currie axles, as far as holding up to years of strip abuse. For just a year or two I'm not so concerned, but if I have to build the center section now, I may as well do the job right the first time so I don't have to change everything in a couple years.

Edit because I wanted to add that MW says on their websight that you can use their 35 spline axles in a large bearing housing, which I have.

I was referring to your Strange iron case and not your housing ends.  I think it's good to have the big Ford housing ends but the iron case for your 31 spline axles probably has a 3.062" bore but you need a different case with the bigger 3.25" bore for the 35 spline axles.  Might be good to leave your center section alone and get a new 3.25" case and build another one with your 35 spline locker.

[Falcon67]

I've been running Mark Williams Masterline 31 spline for 15 years.  Everything from 300 to 500 HP, lots and lots of passes - I won't even guess how many.  2004 and 2005 I had 1916 (one thousand nine hundred sixteen) time slips in a box for just those two years.  The Mustang has Strange 31s, going on 7 years.  Stock cases, stock pinion supports, Timken bearings and Richmond parts.  No issues.

[blykins]

I think you can go 35 without having to change the housing ends.  If you're going to buy a new set of axles and a new diff, I think I'd go as big as possible. 

[afret]

I think you can go 35 without having to change the housing ends.  If you're going to buy a new set of axles and a new diff, I think I'd go as big as possible.

Yup, I think there are bearings that will let you use the 35 spline axles with the small housing ends but he already has the big housing ends.