Mark Anderson

[QUOTE=Mike Simard;8391914]So far I've had half of the fix on my own car and nothing's broken. Someone else has the same thing on their car and they can chime in if they want. QUOTE]

I do have Mike's fix on mine and so far so good.

928mac

It seems that with the race for the high HP 600 and up that a different trans and diff should be looked into.
I see on Carls thread that he has said the case is pushing out under load.
This would make sense for a stock trans/diff to flex when Over Loaded.

Brad

karl ruiter

GO MIKE! Sadly, I am unlikely to ever need this fix, but it makes my day to know someone is working on it.

123quattro

A helical gear is stronger than a straight cut gear.

Vilhuer

What kind of $ we are talking about in here? I have two boxes ('87 ROW S4 and '92 GTS) which would benefit from such fix if its not too expensive.

mark kibort

maybe... but it has more friction, and probably is not as efficient, so thats why the racer boxes have them. I dont know

mark kibort

what is this fix again??


[QUOTE=mark anderson;8392102]

123quattro

Race boxes generally have straight cut gears because they are cheaper to make and more efficient. The synchros are smaller so they just make the gears wider to offset the loss in capacity. Helical gears create a thrust load due to the angle the teeth are cut on. This has to be managed by a thrust bearing, which has associated losses.

AO

Very interesting.

Gonna have to look into this. Hope to be pushing close to 500 RWHP in a few days. Luckily I'm not quite as tough on my trans as the race guys, but I think I would still benefit from this. Happy to be an additional guinea pig if you need.

S4ordie

Dare I offer a guess?

dprantl

So... does half the fix mean only filling the trans with Amsoil half-way full?

Dan
'91 928GT S/C 475hp/460lb.ft

AO

As I understand, it's a mechanical fix.

Even the Kibort uses Redline in the trans...

Benton

A little off-topic, but the crunching at high temps on our track car was dramatically decreased when we switched from Mobilube Synthetic (spec'd on GT3 Cups IIRC) gear lube to Redline 75W-90NS.

I need to do some more research now that I am installing an LSD--are you guys with LSDs using the NS, regular, blend of the two, or regular + friction modifier?

mark kibort

crunching can be eliminated by matching the gears with RPM. I remember, the holbert car "crunching for YEARS, until 2005,when i wanted to have more of the sound of the cup car and started to make high rpm, loud, blips before shifts

its not only true on the S4 gear boxes, but the early cars too. watch my video of racing scots 82. no problems, only some little grinds, but that box had no synchros left, but still driveable

I use a mix of 4 quarts of NS and 1 quart of regular. kind of a blend of what devek recomended back in the day. half and half.

mark kibort

so, they have more pulling apart forces, which could be the issue. none of my helical teeth are gone, just badly chipped. when spur gears break, usually its not at the edges. just a thought. hey, cheaper?? we need a spur gear cut 5th gear set. who has a machine shop and hobbing machine???