j9fd3s

for my PP project, ive spent a lot of time thinking about the trans, as the one that came in the car is bad (3rd becomes neutral when it warms up!)



i made a little spread sheet to look at gearing, also www.yawpower.com has a nice spreadsheet.



after looking at it for a while, i sorta noticed that 5th in the comp gear set, is very close to 4th in a stock gear set. they run a different rear end, and tires.



i have decided to rebuild an old gsl-se trans ive had kicking around, it had new bearings and synchros and forks and stuff, but it ended up sitting so its full of roofing gravel and dirt.



any tips to make it last longer? lynn gave me some, i'll post up in a sec

heretic

Skinny bias-plies and get a Teflon clutch?





Use good gear oil, MTL if you eat synchros, Shockproof if you eat bearings and gears. Bearings and gears are more important. Make sure your driveshaft is balanced and the geometry is correct, or you'll visit horrible things on the tail housing and the layshaft bearings. Sprung hubs are good to have if you're not all out 100% committed to speed, they weigh more but they are much nicer to the trans.



Keep spares. It seems like the more spares I have, the longer they last, but the minute I sell off my last one, boom there goes another trans.

j9fd3s

ive got 3 apart on the garage floor, and i think 4 more outside? people have been giving my "bad" transmissions for a while

j9fd3s

this is what mr Hanover said when i asked him...



In the early transmissions the Mazda people used a key spring with a 90 degree bend at one end.



These must be replaced with a length of piano wire from the hobby shop. The bends made the wire weak and the short piece would break off, allowing a key to stand up behind the slider and leave you stuck in one gear. I don't know if they ever fixed that or not. The piano wire thing works great.



The best thing you can do for a stock trans is to run the lightest clutch disc possible. We used a Tilton 5 1/2" button clutch with two discs. The discs act like a flywheel that makes the synchronizers take a long time to bring the gear mass up to speed or down to speed. Fast synchro wear and ruined sliders is the result.



And now (drum roll) the very fastest shifting stock trans has every other spline removed from each slider and the same on the gears, every other spline removed. So the window that must be hit by the slider splines is now over twice as big as stock. It gives the synchro more time to grip the cones

on most shifts.



Last is the lubrication. Extream pressure additives defeat the synchros, so most manufactures now use engine oil or some lite lubricant. So, use a synthetic trans lube specifically designed for synchronized transmissions. Transmissions rely on many light press fits to hold things in place.



Over heating allows outer races to spin and ruin things. Run a cooler. You can make up two heavy "S" hooks to reach around the end of the tail housing, to hold the stock seal in place. use a hose clamp the hold the "S" hooks in place. Or if you have ribs in that area, you can drill a hole to hold the end of the hook. An over heated trans will kick out the rear seal and dump the oil.



I may be able to remember other things we did, but we have been using either a Saenz dog ring trans or a Richmond gear Road Racing 5 speed. It is synchronized and has every othe spline removed. And they have their own coolers, and they have "S" hooks holding the seals in place.



And when not showing off, slow shifting to make those synchros last a long time. If used hard often

New synchros often.







Lynn E. Hanover

j9fd3s

part 2, edited for complaining about drivers breaking things



The weight of the driven disc is a giant big problem for the transmission. You would think that the clutch people had never talked to a trans designer. Even if a single disc is like 7 1/4 inch compared to two discs at 5 1/2". the smaller diameter is better. Less flywheel effect. I am talking solid discs that are .105" new and .097" worn out.



Have you seen these giant 8 1/2" discs with bronze pads all over them. Maybe 3 pounds each and lots of flywheel effect?



The trans is doomed. You cannot shift at even slow stock speeds without frying the synchros.



Lynn E. Hanover

jwteknix

well at least you have a stock piles of extras i need to get a new tii trans soon

heretic

I've never had synchronizer problems myself, but I'm mean to the trans and this seems to keep the wear surface "fresh". I had one where you could get the car rolling by gently trying to push it into first gear, the synchro was that grippy.



Shifting technique helps a lot too. Gentle pressure on the shifter in the direction you want to go, then stab the clutch as you pull harder. It requires a bit of foreplanning but most things in driving do, need to drive actively not reactively.



An ignition or fuel cut on shifting REALLY helps, you almost don't need to actually disengage the clutch, but an ignition cut can get you kicked off of the track.

Lynn E. Hanover

The synchronizer is a clutch disc. It is conical in shape to give it maybe 3 times the bite of a flat disc. When shifting the slider pushes the synchro onto the cone on the selected gear. The reason for this is that there needs to be zero speed difference between the slider splines and the gear splines, before they touch. When there is too little time during the shift for this speed change, you get a crunch sound/feel in the stick.



Since these are all full constant mesh transmissions, all of the gears (except reverse) are turning all of the time. So the mass of all of those gears is included in the speed increase or decrease required to make that gear change.



So adding to this mass (or flywheel effect if you like) is the clutch disc. The smaller the disc diameter and weight, the less flywheel effect. You cannot run the racing discs on the street. The Tilton and other brands of bronze discs work like light switches. They don't slip worth a damn. Either engaged or not with no slip zone between. New at .105" warn out at .093".



Good for clutchless shifting of a dog ring box and not much else.



So, the synchro changes the speed of everything every time you shift up and down. Synchros have razor sharp teeth inside the cone, used to cut through the oil film and grip the cone on the gear face. When these teeth become flattened the synchro dosn't work any more and needs to be discarded. (recycled).



In dog ring boxes, the driver must match the speeds of the ring dogs and the gear dogs. Since most drivers are skilless in this area, a method of killing the ignition is employed on upshifts. The loss of RPM slows the input shaft to some extent. Usually timed to take the revs down the avarage RPM drop for upshifts. So the speed difference is close enough and many upshifts can be completed with minimal damage. On downshifts, the driver stabs the throttle to help unlock the dogs, and once the dog ring is disengaged, the engine revs up about the same RPM as the RPM increase for that gear change.



This method would be deadly to a synchronized box.



This can only work on dog ring boxes, and then only when the clutch is not used for shifting. Only when leaving the pits is the clutch used.



If you have seen the Daytona Prototypes shifting up, the lever is flexible and has a strain gage mounted on it. When the lever is moved the strain gage shuts off the ignition.



Put in new synchros, it won't hurt a thing.



Lynn E. Hanover