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Matt Monson Matt Monson is online now
gearhead
 
Join Date: Nov 2007
Location: Loverland, CO
Posts: 18,366
Quote:
Originally Posted by puddy View Post
Hi Matt, what do you mean by "timed out" out 2nd and 3rd gear?
In the racing world, we place a service life on engine and gearbox parts. When they have been in the vehicle for a certain amount of track time, we time them out and throw them in the bin and start over. Everyone who races times his engine. Not as many guys are as diligent with their gearbox and time and time again I see it bite them in the butt when they mow down a row of gearteeth like a stack of dominos falling down.

Furthermore, there is frequently this attitude of,"I'm just doing track days and DEs, I'm not racing. It's not the same." True and not true at the same time. I would say that trackdays put 75-80% of the stress on components that racing does, which is significantly more stress than when we daily drive a car. It's really bad with the GT3 guys. They blow up 3rd gears all day long in the 3rd or 4th season of track days.

See the attached picture (sorry for the poor focus, it's a cell phone shot). See the shadow right at the base of the tooth? That's the tip wearing through the heat treatment at the root of the gear. I call it "chopping down the tree". It's how they almost always fail. That gets deep enough and then you get the dominos. This one isn't really bad, but was bad enough that we yanked this gear and consider it junk except for a nice set of used synchro teeth. I suspect you've got at least a couple of gears in there that look like this. This particular picture is a 5th gear from a car that was a commuter and say a lot of highway miles. You can get the wear on any gear with enough use, but the most used track gears are 2 and 3.

Regards,

Matt
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Old 10-27-2014, 11:00 AM
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