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Bi directional vs 45 degree synchro teeth

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ngerk

Probationary Member
24
8
Nov 28, 2016
Odenville, Alabama
Quick question. In the middle of a rebuild and I have two 2nd gears. They are both double synchro but one has engagement teeth that are at a 45ish degree angle and the other is bi-directional. Is there an advantage to either one? On the input the 3rd gear is bi-directional and the 4th gear is 45 degree. I have a 92 input and both 3rd and 4th are bi-directional.

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I’ve tried searching for anything related to this. Finally found one old post where someone asked the same thing and no one ever answered haha
 
I would think the bi-directional would let the syncro engage easier, as it can slip forward or backward to line up the slider with the gear, but I am just going off of every other transmission I have ever had apart. All had bi-directional syncro engagement teeth. I hope Tim pops in and gives us all the expert opinion.
 
I would think the bi-directional would let the syncro engage easier, as it can slip forward or backward to line up the slider with the gear, but I am just going off of every other transmission I have ever had apart. All had bi-directional syncro engagement teeth. I hope Tim pops in and gives us all the expert opinion.
Interesting. I actually have 3 input clusters and 2 of them have the angled teeth on 4th gear. They are both later style. I have asked Tim directly about a gear set someone was trying to sell me and he was very detailed in response. So, I know he could have answered this but I felt bad emailing him multiple times. I figured someone else on here could have answered this. Either way, it’ll be good public knowledge since I couldn’t find an answer searching.
 
What you have there are two, 2G, 2nd gears. The standard cut gears are off of a 1995 car, and the angle cut gear is off of a 96-99 car. Both will accept the standard, 2G dual-cone synchro (MD745896). Both are pretty beat in the pictures.

I've always used the angle cut gears in builds over the years (since I started rebuilding these boxes around 2000), as they are better for up-shifts. I've never had an issue with downshifts with them, but the engagement window will technically be smaller. Never noticed it, but I also don't regularly bang 2nd under high RPMs/load (I don't auto-x/roadrace these cars).

Most builders have used the angle cut version in builds over the years.

Is that what info you were looking for?
 
What you have there are two, 2G, 2nd gears. The standard cut gears are off of a 1995 car, and the angle cut gear is off of a 96-99 car. Both will accept the standard, 2G dual-cone synchro (MD745896). Both are pretty beat in the pictures.

I've always used the angle cut gears in builds over the years (since I started rebuilding these boxes around 2000), as they are better for up-shifts. I've never had an issue with downshifts with them, but the engagement window will technically be smaller. Never noticed it, but I also don't regularly bang 2nd under high RPMs/load (I don't auto-x/roadrace these cars).

Most builders have used the angle cut version in builds over the years.

Is that what info you were looking for?
Yes! Thanks! I agree they are both a little beat. I did deburr the teeth on them. The angle cut gear came out of the trans I was running and it was much overdue on a rebuild. It did not like to 1-2 shift at high RPM at all. Also ended up completely losing reverse after beating on it and discovered the hub and slider was the issue.
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I am curious though, how do you know what year the gears are from? I was under the assumption they were both from a 1G. The angle cut came from my 93 car and the regular was from a intermediate cluster I purchased. The intermediate shaft is from a 92 but I was told he used the better of items he had to assemble it. The gear being double synchro I know isn’t from a 92.
 
The angle cut gears were only *originally* in the 1996 through 1999 cars when they rolled off the production floor.

That being said, the angle cut 2nd gear has been the "go-to" 2nd gear since the late 90's during rebuilds. Also, as Mitsubishi updated parts, a new, replacement transmission for a 1993 car, produced in say...2002, would contain the newer style parts.

So, either someone bought a replacement transmission from Mitsu after they started using the updated parts, *or* someone rebuilt the transmission at some point.

The 93-95 cars had dual-cone 2nd gear synchro setups from the factory, but they were not the angle-cut versions.

The intermediate shafts were all the same in the 1992-1999 cars (MD748830, original part # MD738952).
 
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