ive done a bit of searching and come up with this
all stolen from other forums...
I will attempt to explain although you may need to have the hub, slider, gear, synchro assembly in hand to fully understand.
The springs in the hub push the keys outward against the slider. The keys rest on the slider and move with the slider as you shift gears. When you shift gears the keys mate with the synchro ring and push the synchro ring onto the cone of the gear as you shift toward that gear, this is what matches the gear speed to the slider speed and prevents that gear grinding noise you may hwear with worn synchros. The keys are free to move up and down on the slider but the pressure exerted by the springs keeps the key movement some what in line with the slider movement. The stronger the force exerted on the keys outward toward the slider the more the keys will move with the slider and press against the synchro which mates with the cone on the gear.
also very interesting
If you run two springs on each side of the hub instead of one it can help high RPM shifting, the only downside is that shifting 1 and 2 may be a bit more notchy, but not much at all, it was hardly an issue for me.
I discovered this when a trans came to me with this mod already. I have run it on my car with the double synchro 2nd gear but i dont think it is really all that necessary with the double synchro 2nd gear.
I used to drag race a 4 speed Monte Carlo with a built 355 years ago. All of the transmissions I built for that car, I took off every other tooth on the synchro. It absolutely made the transmission shift better at high rpm especially under a full power shift. However, I would NEVER do this to a street car transmission as it will cause accelerated wear under part throttle shifts as well as making it harder to shift under part throttle. This should be considered a strip only mod, where the transmission will be torn down on a regular basis.
grinding synchro teeth.
Has anybody ever heard of doing this? my dad has been building transmissions for over 20 years he says he used to do that on his old cars. He said he didnt know how it would work on. his words exactly "its either gonna shift like the dickens or grind like a mother ####er"
so after contimplating wether i should risk it or not i decided heh, why the hell not if it doesnt work then i can change it out i have plenty here, so i went ahead and did it but instead of every other tooth he took off 2 teeth left 3 took of 2 then left 3 all the way around, now i was really starting to worry lol.so we put it in and it accually shifts fine, it shifts really good ecspecially at high rpms like 8200 it went in fine no grinding. so i dont know if anybody has ever heard/tried this before but it works great for me.
Robert Bowen discussed this practice briefly on page 163 in his book "How To Rebuild and Modify Your Manual Transmission" . It's a "low-budget way to get synchronizer-free shifting." According to Bowen, Chrysler used this practice in 60's in their drag racing cars due to rules prohibiting aftermarket parts at the time. He says that, to paraphrase, it's a poor man's dog box conversion, although not as sturdy as the real thing, but the gears can be shifted without having to wait for synchros to do their magic.
they are taken off the engagement dog, not the gears
