New rear axle??

I just ordered 36x12.5 SX and I want to know what you guys think of about getting a new rear axle. Right now i have hp44 front and a f9" in the rear. Should i keep the 9" or go to a d60??

Keep the 9...they dont get much tougher.

I say keep the 9 too. Unless you plan on going even bigger in the future, then I would put some thought into a 60. But even if you do go bigger, you can always upgrade the 9 with 35 spline, ctm's, etc.

most 60s are 30 spline full-floaters that aren't a whole lot stronger than your 9". a 31 spline 9", especially with alloy shafts, will hold up to 36s fine unless you're just one of those people that thinks the gas pedal is simply an on/off switch. You could also get 33, 35, or 40 spline axles for the 9" and make it truely bullet-proof. Another issue to consider is the D60 is 8 lug, I'm assuming your 9" is not, so that means changing your front and your wheels to 8 lug too.

Bottom line: Throw some alloy shafts in the 9" and keep the stock ones for spares.

Just a small correction. There is no CrMo alloy shaft made for the 9" ie; 4340 alloy.

This is due to CrMo being able to handle huge twisting stresses without the presence of bending on a semi floating axle.
Stock OEM shafts are usually made from 1040 steel. most aftermarket shafts are made from 1050 steel which is 18% stronger than 1040. The only other option for semifloat axles is 1541H steel which is 20-25%stronger than 1040.

you can build your thrid member with 3.25" bearing journals and a 35 spline locker. 40 spline doesn't have much in the way for traction devices.