9" rear: limits of 31-spline axles?
 

Anyone out there broken a 31-spline axle (please list setup), or know their limit? I'm picking out parts to slowly build a 9" and I'm trying to decide if 31-splines is enough, or if I should step up to 35.

The car is a 6-speed, the setup will be a heads/cam car on a 150 shot (nice amount of torque) using 28" slicks. Will 31-spline axles have any trouble handling this?

31 spline axles
 

I put approx. 700 hp to a set and went 9.30's at 148mph. They held up fine.

I've gone 9.6@143/144mph three times.

But I think a stick car will hit it harder, so I'm not sure how that might work. Sounds like you might be mid to low 10's, so I think that would be okay.

Big Rick is running 31 spline axles in his car. went 8.08 at 172mph (??) Still holding up fine.

Personally, if i were buying a new rear end and putting something in it other than a posi, i'd go ahead and get 35 spline axles. If you're going to run a posi, 31 spline is the biggest you can go.

I also had 31 spline axles in my 6-speed cam/nitrous car, ran low 1.5x 60's and it all held up fine. If only i'd had the same luck with my clutches :bang:

http://www.moserengineering.com/mose...r/axletech.htm

Try that site. Moser's tq rating is 7,000 ft/lbs per axle for the 31 splines.

By that calculator, a 31-spline should be just fine.

Well I think I'm going with 31-spline axles and a detroit truetrac, unless anyone convinces me I should step up to a 35 (in which case I'll have to step up tp a detroit locker). Thanks for the help guys!

Putting down the power you are, I would suggest going ahead and just getting a soft locker. Dont know if the Tru Trac will hold up to well on slicks.

CMC

Really? Should I just step up to the locker tehn, or will a soft locker work ok?

If you go with 31 spline axles you get the "soft" locker. The heavy or loud locker is only for 35 spline axles. Get the locker!

Ohh I did not know that. Good to know!

Definately get the locker, no point in regretting a broke posi later on. I will be selling my 9" with a 31 spline locker in the next few days. So if you are interested in a good deal let me know.

CMC

Sent you a PM

The rate of the springs inside the locker is what determines how agressive the locker is, there are several different rates avalible. Put some real heavy springs in a locker and you'll think soft locker.. Every NEXTEL cup car runs 31 spline axles on superspeedways or road courses..they hold up very well sure they only go a few hundred miles but given the conditions they see... nobodys running anything different.. most of the time it isnt the 31 spline end that fails but the outer crowned driveplate end..(floating axles)

Assuming the same spline counts, I believe the Softlocker is actually stronger than the plain-ol' Locker it replaces.