drivetrain tooth counts

[pauleyman]

I am playing around with some different gears. If what I've found is correct the DSM 1st gear is 3.083 ratio with 12 and 37 tooth counts respectively.
EVO3 1st gear is 2.75 with a 12 and 33 tooth count respectively. What is the difference between the evo 3 input shaft vs dsm input shaft since both of them are 12 tooth?

Similarly it appears the tooth count is the same on the intermediate shaft between dsm and evo3? Is there a difference?

 

[Canadian_CD9A]

Good question on the Evo 2/3 input shaft, the tooth counts seem to be the same as the DSM between 1st and 2nd (heck, 2nd gear is the same ratio). The Evo 1 (with its 2.571 1st gear) has a 14/36 tooth arrangement, so it's different. I'd defer to the experts on the input shaft question, but the intermediate shaft is functionally equivalent between DSM/Evo123.

 

[pauleyman]

Good question on the Evo 2/3 input shaft, the tooth counts seem to be the same as the DSM between 1st and 2nd (heck, 2nd gear is the same ratio). The Evo 1 (with its 2.571 1st gear) has a 14/36 tooth arrangement, so it's different. I'd defer to the experts on the input shaft question, but the intermediate shaft is functionally equivalent between DSM/Evo123.

Intermediate is functionally equivalent yes but now I'm curious if there is some other difference, shot peening etc that I've heard about between dsm and Evo. I know I bought an evo input shaft with evo 1st but the question remains, why?

 

[Canadian_CD9A]

Intermediate is functionally equivalent yes but now I'm curious if there is some other difference, shot peening etc that I've heard about between dsm and Evo. I know I bought an evo input shaft with evo 1st but the question remains, why?

I just checked CAPS for Evo 123 intermediate shaft info, here's what I found:

Evo 1 RS: MD742768
Evo 1 GSR: MD738952, superseded to MD748830

Evo 2 RS: MD742768
Evo 2 GSR: MD738952, superseded to MD748830

Evo 3 RS: MD748831
Evo 3 GSR: MD748830

The Evo GSR part numbers are the same as 1991/5 to 1999 DSM. Those are the same.
Evo RS models were tricky - the ratios were the same, but they got some bonus features. The Evo 123 RS had different gear part numbers as well, and Tim told me that the parts I identified as RS had some oiling channels. Whether the gears and shafts were shot peened or not is up for discussion - the RS did get reinforced transfer case internals and can take more power, but the prices on RS and GSR transmission parts were quite similar (shot peening would have driven the prices up, I would think). If the RS did get shot peened parts, it's kind of moot since you can't buy them new anymore, and the used car parts market doesn't differentiate RS and GSR parts. RS cars were rare, so I would be under the assumption that any intermediate shaft available for Evo 123 is the exact same as DSM.

 

[pauleyman]

For those that read this I'm going to answer one of my own questions. The evo input may have the same 1st gear tooth count as dsm but the dimensions are not the same. I couldn't spot it with just the naked eye but it was clear a dsm 1st gear doesn't mesh.