Treating(cryo, WPC) used transmission gears
 

So I have two broken six speed transmissions I purchased from JayL(along with a working spare). I think together these two transmissions contain enough parts for a complete working transmission.
I would like to try and improve the reliability of this trans by treating the internals-cryo,shot peening then WPC gears, WPC everything else. This is similar to what the MotoIQ guys did with their Nissan transmission.
My question is whether or not it is worth it to treat used gears. Previous history of the transmissions is unknown so how many heat/stress cycles they have been through is unclear.
Obviously to do this right it would be better to start with new gears but a new gearset isn't that cost effective
Of course I would also like to order a transmission cooler as that will probably help with longevity just as much if not more. Just waiting for Savington to get around to building us a kit.
Or I could just pony up and do everything needed to convert to a Tremec unit, but I haven't even broken a 6 speed yet so this seems a bit extreme.

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Cryo makes them "stronger" but more "brittle". The newer thing guys are going is micropolishing the gears. Lowers oil temps and is supposed to make them last longer. RPM transmissions in Indiana introduced it to me several years back. If I ever end up tracking a car, the gear box and rear end will be done.

they are all six speeds, original post edited to make this clear

Starting with a new gearset would be... cost prohibitive. I WOULD start with a known healthy gearset before a cobbled together pile of formerly dead spares, though.

I intend to do with with my 5 speed.

How would you do trans cooler. What pump.

There are a few different electric pumps specifically designed for cooler setups. When Theseus gets one, it will just be run off a manual switch with temps monitored via Racepak.

Transmission shops will "cobble" boxes together all the time, then stuff them into a box with a warrenty and rarely ever have issues. Work with what you have.... But thats unamerican.

Cryo treating doesn't make them more brittle, but actually realigns the molecular structure of the gears removing stresses within the material during it's creation. Cryo treating isn't a hardening process, per se, but a relaxation and realigning process. And it is typically quite reasonably priced (at least here locally). It will slow wear and reduce the likelyhood of fracture under stress.

It would be especially sweet if you spent all the money to WPC treat a gearset, shift rails, shift forks, shafts, bearings, synchros and blocker rings, only to realize that you missed a crack in a gear tooth root and the whole thing came apart 15 miles down the road.

Transmission shops build sheisty street car stuff out of old junk. You don't spend a fortune cryo treating, shot peening and WPC treating mystery meat parts.

Kaiser why not put the money into something like an RX7 t2 conversion? If I sexplode my mazdaspeed 6 speed I may have to do that.

Well again some of this is a thought experiment.
I would like to see if this was useful and it would be nice to have a low mileage gearset but low mileage six speeds aren't exactly common.(there was some guy selling a brand new 6 speed in Seattle that I should have bought).
Since no one makes gears for these motors it seems like the only strategy is to use the 6 speeds as disposable items or upgrade. If I am going to upgrade I am going to go to something like the Tremec unit which is all the transmission any miata should ever need.

where would you tap the transmission for the oil withdrawal [somewhere low] and return [somewhere high]?

same question for the differential?

how hot does transmission oil get?
how hot does differential oil get?

also a 2/gpm pump for a .5 gal volume is 4 volume exchanges per minute?

MX why couldn't you use the trans fill and drain for the suck and return?



Kaiser. Is the car on the road now? If it is, how do you like it compared to your M3? Also, which is your daily? If I got a BMW and fixed my subaru, both of us would have a BMW, modded subie, and turbo miata :) SNUGGLES

From everything I've heard and read when researching this for my STI RA gearset install into the wrx years ago, its a waste of money and time.

Does it harden/strengthen the gears? Sure. By how much? No one has a straight answer to this backed by proof/facts/data, and 99.99% of the people I talked to say its very insignificant at best.
Gear/tooth design is key. Next comes the gear ratios and how much torque shock you get going from 1 gear to the next. Then how robust the shafts and housing is (and how prone it is to flexing). Then of course the material, but re-aligning the molecules or whatever it is, doesn't really change much about it. It still wont hold much more power or hold up with heavy abuse.

The 6speeds in our cars are not stronger than the 5 speeds due to having harder metal in their gears/teeth, but from having a different design and ratios.

Just my .02

something else to hang down, get broken, leak, leave you stranded;
[hell that sounds like an old man's pecker]

from Wikipedia "In petrol (gasoline) engines, the top piston ring can expose the motor oil to temperatures of 320 °F (160 °C)." ouch!

engine oil temperature gauges 100*F - 300*F

transmission oil temperature gauges 100*F - 150*F

perhaps a 100*C [212*F] rated micro-pump would work for transmission and differential [less weight, smaller current draw]

use small power steering fluid cooler for radiator, mounted in the rear wheel well, but shielded from wheel-tossed objects, [source - pull-a-part]

wonder how many take the cooling loop off the clutch circuit. I did, and now I am second guessing myself. we know the transmissions get hot, how much heating of the slave cylinder and would that affect performance, longevity

I got too much time on my hands, need to get my car back
per Stephanie, install is complete and car will be started for the first time this week

http://www.raceshopper.com/brake_fluid.shtml

Not worried about heat from the clutch.

Can you guys run a thicker Amsoil in the gearbox? If their propaganda is half right, the 80-90 is better then others 140w oils in terms of shock load. Run some of the thicker stuff in it and hope the housing isn't deflecting a bunch.

already have the Motul in the clutch and brake systems
run a high quality AT fluid in the tranny

The cooling loop has nothing to do with trans fluid temps.

You have to remember that we're talking about an increase in fatigue resistance, not outright strength. If you abuse the transmission with WAAAAY too much torque, or really serious shock loads (unsprung pucked/ ceramic clutch disc), you're still going to break a marginal/ too weak transmission, no matter how much fatigue resistance yo give it.