Increasing Gear Durability
Increasing Gear Durability
(OP)
Hi, I'm a Mechanical Engineer by education and a Racecar Engineer by trade and I have a question I've not been able to answer anywhere else.
I'm building a transaxle for my street car and need it to last with the added power I'll be putting through it. The car is a '94 Toyota Celica ST with the C52 Manual Transaxle. When all is said and done I'll be making about 300hp at the crank and it will be a daily driven car. Aftermarket gears are not available, they would have to be custom and would likely be very costly.
I have a spare tranny that I started disassembling today and there was visible wear on the pinion (not so much on the ring gear). I haven't had much time to look at the other gears but they looked ok on first inspection.
My question is this: What treatments are available to increase the strength and durability of transmission gears and which of them work? I've read everything I can find about Cryogenic treatments and they seem to work although nobody knows why. I've had our racecar transmission REM treated. This seems to lower gearbox temps and reduce friction but I doubt it really does much for durability (other than the obvious stuff less heat does for you). I've also heard of shot-peening gears.
What does everybody think?
Thanks!
John Dolecek
Team Engineer
Wheels America BMW
I'm building a transaxle for my street car and need it to last with the added power I'll be putting through it. The car is a '94 Toyota Celica ST with the C52 Manual Transaxle. When all is said and done I'll be making about 300hp at the crank and it will be a daily driven car. Aftermarket gears are not available, they would have to be custom and would likely be very costly.
I have a spare tranny that I started disassembling today and there was visible wear on the pinion (not so much on the ring gear). I haven't had much time to look at the other gears but they looked ok on first inspection.
My question is this: What treatments are available to increase the strength and durability of transmission gears and which of them work? I've read everything I can find about Cryogenic treatments and they seem to work although nobody knows why. I've had our racecar transmission REM treated. This seems to lower gearbox temps and reduce friction but I doubt it really does much for durability (other than the obvious stuff less heat does for you). I've also heard of shot-peening gears.
What does everybody think?
Thanks!
John Dolecek
Team Engineer
Wheels America BMW





RE: Increasing Gear Durability
RE: Increasing Gear Durability
RE: Increasing Gear Durability
Oh, and magnaflux ANY new or used gears you plan to use to see if they are pre-cracked or have surface defects that may be polished out.
It sounds like you feel wear may be your immediate concern. First I'd determine if what you saw is indeed wear, or simply a polished well broken in surface. Even if the surfce condition "wear" is normal, you may need something more at higher outputs. Then high viscosity lube is full time solution. Beefing up anti-wear and EP and surface treatments are useful short term, or to help things survive being "worn in."
To make gears less likely to crack under heavy or especially impact loads, deburr and polish the roots and edges, then shot peen with propely graded steel shot to the appropriate Almen spec.
RE: Increasing Gear Durability
Or just don't drag race your celica, shift it smooth and don't drop the clutch at 7k and it will likely out live your engine.
RE: Increasing Gear Durability
RE: Increasing Gear Durability
Perhaps the condition I saw could better be described as 'deformation of the tooth surface'. Its hard for me to explain. Its not like the teeth were dramatically bent, but it seemed like the driven side of the teeth had been compressed slightly. There seemed to be some localized expansion along the axis of the gear.
RE: Increasing Gear Durability
None of that sounds like normal failure modes in a transmission gear. I would (and did) get ahold of the Dudley or Drago books and compare their pictures to my gears.
Its probably too late to ask the transaxle "sweetie, where have you been?'
RE: Increasing Gear Durability
RE: Increasing Gear Durability
RE: Increasing Gear Durability
It is possible to increase the life of gears but most options are not realistic:
*Use a super-clean steel - CEVM or low oxygen content
*Super finish - surface fatigue is directly related to contacting surface quality
*(Carbo)Nitride - you could find a local heat-treat house to anneal back and then reheattreat your gears in an carbon+amonia atmosphere. The functional surfaces need to be redressed following heat treatment.
*Synth oil - really only useful if you are in a marginal lubrication situation (it won't hurt but may not help enough)
*Cryo treat - probably the easiest and a proven fatigue aid but be sure to start with good (used not worn) parts
On your gears, it can be hard to tell what is a physical or merely optical feature. If you have gears where material has been removed in the contact zone - that is wear. Most likely it is advancing surface fatigue that gets polished by continued operation. New oil will help but nothing will undo the damage.
RE: Increasing Gear Durability
RE: Increasing Gear Durability
RE: Increasing Gear Durability
RE: Increasing Gear Durability
http://www.bostongears.com
Good luck
RE: Increasing Gear Durability