FAQ: Crash Box - Semi-Synchro Gearbox

[TurboGLH]

Authors: TurboGLH
Last modified: 7-31-05
Stage: 100%
Type: How To

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WARNING - This has been done only once on a TD, and as such is considered experimental. I am not responisible for any damage you do to your trans (parts or as a whole) or to your car. Be a man and take responsibility for your actions

Years ago it was popular to modify the synchro assembly to aid in faster shifting. I built one for my hybrid 16v but it ended up in someone else's car when I bought an srt-4 instead. I've got some pictures as visual aids, they're from the srt service manual but they'll do.

The premise here is simple, while the synchro assembly's help make the trans easier to drive, they require more force to shift than a non-synchro gearbox. We still want some stree maners so we're not going all out, but we are going to remove half of the teeth from the brass and half the synchro teeth from the gears themselves.

Picture 1 - This shows the brass synchro gear
http://boostedmopar.com/forums/images/faq/trans/man/3.jpg

Picture 2 - In this picture I've marked off every other tooth on the gear. Fix the gear in a vise (gently, it's brass) and mark every other tooth with a black sharpie, now go around and grind off the teeth that are marked. You will find that sometimes that the number of teeth are not even and you have to grind off the last tooth in a section, thats normal so just go with it.
http://boostedmopar.com/forums/images/faq/trans/man/4.jpg

Picture 3 - This shows one of the gears that rides the mainshaft.
http://boostedmopar.com/forums/images/faq/trans/man/5.jpg

Picture 4 - Same as in picture 2, fix the gear in a vise and mark every other tooth, same as with the brass not every section has even numbers of teeth. Now grind off the marked teeth.
http://boostedmopar.com/forums/images/faq/trans/man/6.jpg

This will take some time and patience. At this point there is only one of these out there and it took me about 10hrs to grind all the gears and brass. It's not for the weak of heart, you are grinding away material from a set of gears that are getting harder to find every year. Properly done this trans will shift faster but will require you to match engine speed better. Learn to drive :)

[TurboGLH]

There are some actual pics from the build, but they're on my fathers computer. I'll get him to email them over to me and I'll add them to the FAQ.

[Frank]

Cool. Just let me know when you are done, and I will combine any posts, and move it in.

Thanks!

[GLHNSLHT2]

so do you have to double clutch? will it grind on each upshift? what about downshifting? I heel and toe pretty good just curious as to what you mean by having to "drive better"

[TurboGLH]

so do you have to double clutch? will it grind on each upshift? what about downshifting? I heel and toe pretty good just curious as to what you mean by having to "drive better"

I sold it when I bought my srt-4 and cancelled my dohc project. It went into Jon Geneski's csx-t racecar so it could be tested in a tough enviroment, and it's still there to this day. He said that it drove great. Shifted smooth, fast and easy. No double clutching, no grinding, just FAST. I guess what I meant by drive better was, if your 17 and this is your first car with a stick, this might not be for you, so get a little more wheel time and come back. But if your a little older or have some time in a stick car you should be ok.

[Aerosmith145]

I think it may be worth the effort to make sure the brass synchro ring maintains the pattern (pitch: tooth, tooth gone, tooth, etc..) AS you travel over the factory toothless areas. In other words, try not to accidently invert the pattern when you cross that empty section. Or else it will still engage as if it had all the teeth (factory pitch: tooth, tooth, tooth, etc..).

Maybe?

[Reaper1]

Subscribed...basically so I can find it when I ready to try it!

[zin]

interesting....

Mike