Shot Peen Bay Area

[beta]

So I'm about to pick up some 3.91 gears, got a great price and I couldn't resist.

I want to get them shot peened (like the 4.10 gears), but I want to make sure I get a reputable shop, since motorsport parts have no warranty. Anyone know a good shop?

Google only found me one place in walnut creek http://www.morgansspeedshop.com/

[mfanatic325]

What's shot peen? I got mine REM-polished by Performance Technic in Pleasanton, but I doubt that's the same thing?

BTW, grats on the gearing

[beta]

They're somewhat similar processes.

REM polishing is a proprietary chemical process, it polishes the surface at a microscopic level to make it extremely smooth. This reduces friction, reduces heat, etc.

Shot peening is literally shooting it with round metal/glass/etc, this covers the surface in tiny dimples. The dimples reduce fatigue and stress failures, as the compression of the surface prevents cracks from happening. It also makes the surface hardness higher.

BMW chose to shot peen the 4.10 gears from the factory for at least two years, I read on another forum that the last batch of gears came without it.

My thinking for choosing shot peen over REM is the diff shouldn't make any noise if properly installed, so I'm not so much worried about friction as I am of making the gears last for as long as possible.

[mfanatic325]

Maybe I just got lucky, or perhaps Performance Technic did a really good job, but mine doesn't have any grinding noises at all. I'm about to flush out the diff fluid before my July 8th track day @ Laguna. Hope to see relatively clean fluid...you know, with no metal bits in it and stuff?

The guys at PT have done auto-x and track work for many years and they recommended I stick with the OEM fluid when it comes to the differential, because they've literally tried everything and have found the least amount of NVH from the SAF-XJ fluid. I think at most, mine has a slight whine to the diff, if anything. And only at certain rpms. I personally kind of like it though because it sounds more like a racecar

[mfanatic325]

By the way, maybe give Phil Wood & Co. in San Jose a ring? An acquaintance of mine runs that company as a family business, and I toured their factory last time I was there. They've been around for YEARS making high-end bicycle racing equipment such as a hubs, sprockets, etc.
I hear that their bicycle stuff aren't cheap, but the quality in each part they produce reflects that. Even if they don't have shot peening service available, at least they'll be able to point you in the right direction I'd bet? Good luck!

[beta]

Yeah PTech is great, they've done all the work on my car and I've been happy so far.

Thanks for the lead, I'll give them a call and see if they can point me in the right direction.