I am finally getting a limited slip for my FB and I am considering having the ring and pinion shot peened to strengthen my rear end a bit. I just spent alot of time researching shot peening vs cryo treating etc. to see if any thing actually makes a difference. I've been pushing roughly 300whp and a bit more torque through my open diff for a couple yrs and it's holding up just fine, but I would like a little insurance in case I ever want to launch the car. I can't really seem to find an overwhelming answer, because as always, the internet is a sea of contradictions; so I thought I would see if any one here has any thoughts on this metal vodoo.

 

Sorry I have no input on the which is better part but, whats cheaper having them done or a second set of gears when they pop?

 

Mazdatrix does some sort of shot peen process, or they send parts out to a company that does it. I've only seen it on their web page so I have zero personal experience with the process.

Isn't it a surface hardening treatment only? Good for anti wear but probably not for running big torque through it as the metal under the surface is stock strength.

 

Like Jeff20b said shot peening is a process that brings carbon to the top of the metal making for a very good wear surface but really does not make the part any stronger . Without getting into what you have already read 100 times IMO you could better spend your money somewhere else on the little car . You can't make jam from peanut butter , I would buy another diff for a spare and launch away . Gerald m.

I'm not sure but I think for best results you would need to start on a part that has high carbon content . A great process for say a shaft that will have needle bearings or some such thing running on it .

 

Simply awesome!

 

I haven't had anything cryo'd for a street car, but have had stuff for my rock crawler done. I'm still running the R&P, seem to be holding up better. This is with large aggressive grooved tires, a Detroit locker, and with pretty hard shock loading on the rear end. Its been about 3 years, only cost me $50. Only stuff I have that is shot peened are AR-15 BCGs.

 

The gears themselves are okay.

If I were going to bother with strengthening the center - and I'm not, since I have way more problems with the flexible floppy rearend housing that twists or bends or just plain cracks - but if I WERE then the first thing I'd do would be to replace the weak carrier bolts with some high quality studs. 3lb overtorque on the carrier bolts will stretch and break them! If the caps shift backwards under load, it doesn't matter WHAT the gears are, the mesh will go off and you'll wreck them.

But I'm not having a problem with that, so I never bothered. I do replace six of the centersection to housing bolts with 8x1.25x40 button-head bolts inserted from the inside. Tap the carrier threads the rest of the way through and insert the new bolts from the inside. I put a washer and a dab of RTV on them before installation. I've had proiblems with housing distortion pulling the threads out of the housing.

 

Well you've given me plenty to think about here. I think I'll invest in some ARP hardware and continue my no clutch dump policy and I should be fine.

 

For those that have failed a rear end, where did it break?

Shot peening, cryo treatment, and LOWERING the hardness of gears are all well established techniques to reduce the likelihood of cracks forming and gears failing. The higher $$ drag race setups typically use at least two of these methods. If the failure mode for FBs has been sheared or broken gear teeth, I would consider it (especially since it usually doesn't cost that much).

 

I personally ripped a bunch of teeth off the ring gear. 250whp