Do you think the cryo'd gears are lasting better?

After the one Cryo set crapped out, I put one of the old sets that I took out back in....ran it for 2 more years.

I had to replace one of those gears due to part of the edge of the brass ring was peeling off, late last year.

Otherwise it looked good ( no pitting)...it was an older set, that pre-dates the junk they're putting out now.

So, I cant tell if they're lasting any longer or not.

I experimented with various coating, heat treating and cryo processing of both upper and lower gears, I found that cryoing and polishing the gears along with running amsoil and lucas additive -on the advice of Max machine worx) seems to make them last 2-3 times longer under hard use (from pitting and galling) but does nothing to keep teeth from breaking and failing. I have 2 drives for my boat, both have old merc upper xr gears in them that have been run at over 1000 hp in my 2000 272 baja (a lite boat) and the uppers set up right have just lasted and lasted. Lowers however, were only lasting 10-15 hours before they were completely ate up, since settling on this cryo/polishing combination and the mentioned oil package last me 40-60 hours now though. I also tear my drive down and inspect it every 15-20 hours, I have found failing bearings, cracked upper shafts, sheared off billet prop shafts and vert shafts but again , i am running over 1000 hp and 1000 ft lbs of tq, Smitty
I still have the treatment applied to customers gears on a custom special order basis for customers on a custom basis

I wish Merc would have bought me out or funded my research but what really happened was I was trying to get lower gears to last and looked into having custom sets built with the assistance of RM Builder/Bob Madera, we sent sets out and had the mettalurgy tested, dimensions copied, etc with the intentions of having some built, we found one supplier that had already built experimental sets for Max worx that lasted less time than stocks ones and we were at the point of spending 10,000 plus dollars on a few test/trial sets of lower billet gears but my phone quit ringing with guys that even wanted stock ones treated let alone custom built ones and a short run after the experimental sets were going to be done was still going to be 50,000 plus dollars with no guarantee that they would even last as long as stocks ones! At that point, the need for upper gears seemed to be the biggest problem I was hearing about and everyone that has looked into having them built found it was going to cost well into the six figures again with no guarantee thery would last or even work. The gears are near net forged, the only way to have a gear with any real strength made would be to have forging dies and a capable company do it . cnc'd gears wouldn't have the root strength being "cut" not forged due to the grain structure unless some really exotic material was used and even then it still a 250,000$ flip of the coin, I have spent enough money already experimenting to get where I am at so I am having lowers and uppers cryoed and polished but again, I have 2 sets of the early "good" xr gears in my drives.
As far as aftermarket gears, I know for a fact there are aftermarket low qualit lower gears already out ther, the Chinese are using them in there 800$ lower bravo, there is no way they are buying 400$ lower gears to put in a 800$ drive, thing is, they don't offer them for sale and I don't think you would want Chinese gears anyways, Smitty
I was fortunate in this down turned economy to land a second job with a low six figure income, thing is I am still working 40 hours a week at my old job until I can retire and running my transmission/performance business with the help of my youngest son who I trained for 10 years so I am busy or gone 96 to 120 hours a week, doesn't leave much time for running/testing trial sets of gears anymore!!

Smitty, Thanks for taking the time with your busy schedule to give an update. Sounds like we need your work here more than ever given the low quality XR upper gears Merc is now selling.

What of all that you learned trying to improve the life of your lower gears with ~1000hp do you think could be applied to improve the life of a current set of low quality XR upper gears at ~600 - 700 hp where they are now prematurely failing?

You mentioned that when you tried re hardening your lower gears to provide a thicker/deeper hardened surface" After 17 hours they were chipped up exactly the same as the oem's,only difference was the little craters were much deeper because surface hardness was thicker." Do you think that that might improve the life of the current XR uppers for the lower torque levels of a 600 - 700 hp engine along with cryo treating as well? Same question plus the addition of nitriding?

I guess a better question would be what would you do to best improve the wear life of the current low quality XR gears for a 600 - 700 hp application?

Thanks for any suggestions.

Bill

Hello Smitty:

Did you ever try QPQ nitriding on the gear sets to see if it helps the surface wear and pitting of the XR gear sets or lower gear sets. It won't obviously make the gears internally stronger but we've seen very good results on items we have QPQ Nitrided for surface strength and ductability as well as surface lubricity and increased metal strength .003" to .010" into the material.

Best Regards,
Ray @ Raylar

Geezus Ray now ya tell me!!!!!

No, we tried deepening the heat treatment and also tried DLC (diamond like coating) and because of the movement below the heat treated area the surface (or picture a egg like shell) still flexed and gave away, we had sets professionally analyzed with destructive testing and electron microscope exam, the final opinion was the substrate was allowing too much movement in the base metal under neath the hardening and nothing else could be done without new base metal. The cryo/iso treatment does seem to keep the surface from galling as easy but switching to amsoil severe gear did wonders too over all the other oils I tried, the royal purple I used was absolute GARBAGE, I wish I would have realized that sooner during my testing. I did try swepco and some others, did nothing , Smitty
As far as the new XR uppers, I hear that they crack and break with no rhyme or reason, the cryo iso will help keep them from galling but from everything I keep hearing they will probably break first, Smitty

Bill, it seemed like the heat treating just made the gear more brittle/ chips were deeper which could be expected when re-heat treating something already hardened, it was of no help, Smitty

Thanks.

In addition to using the Amsoil HD gear lube plus the Lucas oil additive and the cryo what would you do in addition to the current low quality XR gears to improve the wear life for a 600 - 700 hp application?

Bill