Bi directional vs 45 degree synchro teeth

[ngerk]

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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[ngerk]

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

 

[EC17PSE]

@twicks69

 

[1990TSIAWDTALON]

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.

 

[ngerk]

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.

 

[DSSA]

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?

 

[ngerk]

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.

 

[DSSA]

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).

 

[ngerk]

Good info, Thanks!