slick shift/pro shift/crash box modifications FS571 Trans

[scooter]

Morning boys and girls,

 

I stumbled onto this article describing old school drag racing mods to chevy and chrysler trannies back in the day.

 

It involves grinding every second engagement tooth off 2nd 3rd and 4th and every second spline off the sliders and taking the teeth off the synchros.

 

The theory works the same as using face plates - dog rings. you are making the engagement system coarser so you have a better chance of slamming it into the next gear.

 

Not good for street drivability (tons of slop in the tranny) but good for fast shifts at the drag strip... 

 

So has anyone of here tried to do these mods on a datsun tranny before? Im kinda tempted to get the guts from one from pick a part and give this a try. 

 

heres the article i was looking at http://www.atraonline.com/gears/2006/2006-05/2006_05_60.pdf

 

I'd love to hear if any of you guys on here have done this in the past.

[G-Duax]

Ah, Very interesting !

 

 

I have hand stoned bike dog teeth before so I could shift under full throttle, without using the clutch.

 

Grinding all those splines, without touching the ones next to them will be a challenge, but I'm game.

I'm thinking of a jig that holds my die grinder, and engages the splines so the stone can only grind the one I want.

Just happed to have a spare 71B, that the main shaft nut had backed off of, that will be OK if I can just find two of the synchro parts that got chewed up.

 

[Stoffregen Motorsports]

Even during the height of Datsun racing popularity, during the 90's, when I was building racing Datsun transmissions, that was a mod that I heard about but never witnessed. I never tried it either. There was a racer named Jamie Housman (sp?) that built dog box gearsets for Datsun transmissions back then. They didn't use synchros at all.

 

If you have ten hours to spend grinding, I'd love to hear how this turns out...!

[datzenmike]

What's wrong with the way it shifts normally? I can only see this in a drag race where everything is about time. This will just encourage abuse leading to wear and damage in a street car. 

 

What happens with a modified transmission if you shift slowly in a normal manner? Does it grind more? less? easier? or just faster?

[scooter]

3 hours ago, datzenmike said:

What's wrong with the way it shifts normally? I can only see this in a drag race where everything is about time. This will just encourage abuse leading to wear and damage in a street car. 

 

What happens with a modified transmission if you shift slowly in a normal manner? Does it grind more? less? easier? or just faster?

Mike you wouldn't want to do this to your daily for sure..  This mod is what the old school drag racers did before Lencos and Jericos existed.  its not good to drive to the gerocery store as there is a bunch of slop in the engagement system. you can shift these normally but will have a bit of crunch if you shift slow (same thing happens with dog trannys) 

 the only gear you don't take extra off is for first gear, as you usually need all the strength you can get for launching at the strip. 

there is definitley more wear on the slider and gear teeth, but for race car use this can be considered acceptable. 

 

The way you would want to drive this is either ON throttle or OFF, and shift it like a pissed roid monkey.

 

I dont think this would be a good idea for a road race car either as I think the gears would get eaten up pretty fast and sees more gear changes in a session than a drag car does in a season

 

[scooter]

it looks like I need to get another tranny from pick a part as i have taken my trans completely apart and 2nd,3rd sliders are pretty mashed. also had a broken 1-2 shift fork. The guts from this current one may get donated to this project. if i can get another 71b bell i'll start this project once i get a minty trans back in the car.