grinding ever other tooth off the synchro

[compression]

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 my car, 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 .so we put it in the car 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.

 

[wishihadatalon]

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 my car, 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 .so we put it in the car 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.

I talked to Jon at TRE about this and he said it was probably the dumbest idea he has ever heard. Think about it, all you are doing is making the teeth you didn't grind off take the load of the ones you did, which will just hurt it more.

 

[TSIfreek]

Not a good Idea you will weaken the syncro by doing so. Double synco is the only way to go.

 

[slipstream808]

I'll admit it sounds dumb. BUT if you think you can, then go for it!!

Daily drive it, drive the balls off it, drive it in every condition and way you can think of. Then bring us back the results and see what it looks like on the inside, trash magnet and all. I'm curious.

Don't let everyone discourage you!!! You've done it and it "seems" to be working. No point in reverting it unless it breaks. I'm just saying you've started walking down the road, might as well go all the way. Best of luck and props on being bold!!

 

[unior]

i'd just like to know the logic behind doing it in the older cars...just curious - the fact that a dsm transmission shifts at 8200 is an accomplishment in itself

 

[wishihadatalon]

i'd just like to know the logic behind doing it in the older cars...just curious - the fact that a dsm transmission shifts at 8200 is an accomplishment in itself

Not really. Mine always shifted high with no issues at all.

 

[Elvenhome21]

I have heard of that before, I think the guy I heard it from was an X-Pro Stock champion. It sounds dumb but it isn't the first time something like that makes a person think why the hell would you do that, and it turns out that it works great for some reason.

 

[MIdsm]

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.

 

[unior]

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.

hmm so what happens to low rpm drivability

 

[RipperXX]

This is a old muscle car/drag racing trick, back in the day before we had real nice trannys, they would do this. At high speeds/rpm's it helps because theres less teeth that have to line up for it to go in gear.

I only know about this because my father has seen it done first hand, and was telling me about it. He's a 62yr old GM master tech thats been a tech since he was like 20. Sooo he knows what he's talking about.


Now would it work so well in our cars, I duno. The concept is still the same, however I dont think it will take the added stress like the old RWD domestic trannies do, for near as long.

 

[wishihadatalon]

This is a old muscle car/drag racing trick, back in the day before we had real nice trannys, they would do this. At high speeds/rpm's it helps because theres less teeth that have to line up for it to go in gear.

I only know about this because my father has seen it done first hand, and was telling me about it. He's a 62yr old GM master tech thats been a tech since he was like 20. Sooo he knows what he's talking about.


Now would it work so well in our cars, I duno. The concept is still the same, however I dont think it will take the added stress like the old RWD domestic trannies do, for near as long.

I don't see how less teeth lining up is going to do anything if the space between the teeth that are left there is still the same. The remaining teeth still have to fit in the same size slot so all you are doing is transfering the stress that the other teeth would have taken and are putting it on the one that are still there.

 

[RipperXX]

Well, when my father told me this, he said every other tooth on the "gear" im not sure if he was talking about the actual gear or the synchro. I assumed the gear at the time.

All I know though, is my old man and a few others did this back in the day, and it worked.

 

[Defiant]

They're taken off the engagement dog, not the gears.

 

[DSM007]

i'd just like to know the logic behind doing it in the older cars...just curious - the fact that a dsm transmission shifts at 8200 is an accomplishment in itself

And I see compression drive it almost everyday like that......Im surprised it shifts at all it being an older single syncro second gear at 8200 rpms.

 

[groundPork]

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.

There's an old guy where I work, who used to do it to muncie trannys, when he used to drage race, and said the same thing "poor mans, dog box" he didn't think it was a good idea for modern smaller transmissions though.

I think maybe the lack of difference in his trans engagement, may be cause he was supposed to remove every other tooth to provide more space between the teeth.

Also, someone asked what the difference would be , just guessing here, I think with the extra space the hub and gear would just slam togather, not allowing the synchro blocker to brake the shaft speeds to match eachother. This unfortunately would also where out the actual cone synchro interface I think...

I think it's bad ass he just went for it to be honest.

 

[jking29]

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.

 

[Elvenhome21]

It's amazing how many chevy guys are on here.

But I would try doing this on a road racing/autocross transmission if I ever have to tear one apart

 

[raped]

if you are on a tight budget, and do not have the cash to spend for the double second gear setup you can double up the springs for the keys on the 1/2 slider. Shifting will be a bit more notchy at low RPMs but it will shift much better at high RPMs.

 

[1990talon]

Made chevys shift like butter at high speeds my truck had this done before the auto went in.

 

[groundPork]

if you are on a tight budget, and do not have the cash to spend for the double second gear setup you can double up the springs for the keys on the 1/2 slider. Shifting will be a bit more notchy at low RPMs but it will shift much better at high RPMs.

caught my interest, care to elaborate on exactly how this works?

 

[1990talon]

if you are on a tight budget, and do not have the cash to spend for the double second gear setup you can double up the springs for the keys on the 1/2 slider. Shifting will be a bit more notchy at low RPMs but it will shift much better at high RPMs.

Will tranny shops know of this?

 

[raped]

caught my interest, care to elaborate on exactly how this works?

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. 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.

 

[bastarddsm]

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 my car, 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 .so we put it in the car 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.

I belive they call this a crash-box, Mr. Gasket used to sell synchro kits for doing this. My dad has an old ford four speed that has this done, along with some other stuff and it will almost make a complete downshift or upshift ( can't remember what he said) on its own when you let off the gas...good for a race car bad for a street car!

 

[Defiant]

I belive they call this a crash-box

They may call it that, but a crashbox is simply a transmission with no synchronizers. Sadly, the language is going down the same toilet that everything else is.

 

[Elvenhome21]

Is there a double syncro kit out there for 3-4-5 gear or will the double spring work in those clusters with grinding everyother tooth off.