UPDATE-


These seems like a common weak point for guys making a lot of torque. 4th gear has to be the most overworked gear for road racing. There has been attempts to create better cooling to 4th gear to help prolong the life of 4th, but we believe this should 100% cure the issue from happening.

Ron at RSMotors is currently going to test this with several back to back pulls in 4th on his dyno (Winter here so no on track testing for a few months).

This gear also changes the 4th gear ratio to 1.0 giving you a few extra mph's in 4th which will also reduce the wear on the 5th gear synchro and help decrease the large gap from 4th to 5th.

Evo 8- 1.031
Evo 9- 1.096

Assuming Ron's test passes, we want to organize a larger group buy to save on costs. Depending how many we get to commit, cost will be in the $700-750 range.

 

Waiting for a vid clip of the sound... :}

 

ditto

 

In for results

 

In for results.

If the 4th gear problem is simply heat, this may fix the problem. Especially since a spur gear is inherently weaker than a helical cut gear, so the metallurgy in the spur gear has to be far superior. Yes, I know that spur gear will make less heat. I still wouldn't jump on it until its last longer than the stock 4th under similar stress.

 

Heat is always the enemy. however I've seen the 4th break on the first out lap. I think the 4th in general is weak, then add heat and its only a matter of time before it gives out. Also my trans had 5000 miles on it when 4th went. Ronnie's had only a few thousand was well.

Helical gears produce a lot of thrust load in opposite directions. Perhaps if enough shaft play, they can push each other away enough for bad things to happen. The straight cut gear would cure that problem and also reduce extra heat generated by the side load.

Regardless, this trans is heading to Minnesota this weekend where Ron plans to do some dyno testing with it.

 

that 4th looks BEASTLY this plus TRE cooling and syncrotech syncros for all other gears = WIN

 

The thrust they create is hard on bearings. The heat comes from the helical teeth sliding across each other. There is no doubt that the spur gear will help with heat. The issue I can see is that two gears that are identical in every way except spur vs helical, the helical is stronger. So the spur gear needs to be superior metallurgy, design, heat treat, etc. Which is why it needs to be tested, and it will be awesome if it works out.

How much power/torque are you guys making that fourth gear goes in such short time? Are you running taller final drives that put you in 4th gear a lot more of time on track?

 

100% stock trans/gearing. 2 of us were on stock evo9 turbos. Its the torque and how hard it comes on that will kill the 4th gear.

 

Add a third for stock trans and Evo 9 turbo. Torque kills.

 

they make dogbox for rally ? If they do can i get a shorter and higher engaging 5th gear

 

 

^ Dear Lord! I would rip my ears out! :}

 

racecar parts make racecar noises...

 

well, 4th gear made it through our little stress test. several back to back 4th gear pulls. 430ft/lbs of TQ. 2k rpms to 7500rpms. No issues at all.

I'll post up more later with dyno graph to show you the torque curve. If any car eats 4th gear its this one.