Road course guys - 3.9 gears

[Slow*Jim]

I just realized that replacing final drive is on the list of zero-point mods in NASA TT. Can anyone who has driven on a road course (specifically Mid-Ohio or Putnam Park) chime in? Will this improve my times or will it turn third-gear corners into 4th gear and screw everything up?

[mpowers]

Can't comment on those tracks, but be careful as we had the 4.09 gears. The extra heat generated was enough to melt all the seals. Going to reinstall them at a later date with a diff pump and cooler as they were well worth it.



mpowers
note: this failure happened during a three hour enduro so a 20-30 minute run you might get away with it all day long.

[Fluid1]

I didn't see anything about a diff cover/cooler (nismo finned) on the list of points or non-points mods. Anyone know? (NASA TT)

[betamotorsports]

Its at least a 1 point mod.

[Fluid1]

what is, the diff cover?
"at least 1" lol

[betamotorsports]

I was wrong. Under No-Points Modification: 11) Final Drive Ratio Modification.

Rear gearing tends to be track specific so it requires some testing to determine if a chage helps.

[laze1]

I don't have "gears", but it is on my wish-list. I plan to build up a 4.09 "pumkin" but I am unsure about what LSD to use...stock VLSD or aftermarket.

BTW: MPOWERS sez he runs the stock VLSD....and he is FAST!

But the folks that do have them say it is the cheapest mod to improve acceleration (as apposed to Turbo/Super Charge?cams/head work/etc)

The 3.9 gear is obviously is less dramatic change than the 4.09 gear...there are several threads here that cover the rpm/mph change, and technical requirements to install these...

[Fluid1]

laze1- Quaife ATB LSD and the 4.09 gears are exactly what you need.

The quaife, unlike all others, has what many call "yaw control"

PM me for more info if you don't just trust me.

I'm going the 3.9 route

[betamotorsports]

The quaife, unlike all others, has what many call "yaw control"

As some who's raced a number of cars (both FWD and RWD) with Quaife differentials, I am curious what you are referring to as "yaw control." I was just on the phone with Mark Ortiz regarding another subject and I asked him about the term. He's curious too. I do know of "Active Yaw Control" and that's done with electronically controlled active differentials (ECAD) and the Prelude SH was one or the first production cars to use this tech.

Does your term "yaw control" refer to the designed in torque distribution of the Quaife? If so, how does it control the yaw rate of the chassis different from a CLSD with some set lockup (80% lets say)?

I'm not challenging you, I'm just curious because I've never heard therm used with a passive differential.

[laze1]

I trust you, I have heard from many folks that the Quaife is the best on the market......but the Quaife is pretty pricey, and hard to get.

But I am very CHEAP, and actually have not had any problems with my VLSD.
But maybe I am not driving fast/hard enough

So I just plan to get a used VLSD complete unit(pumkin), and stick some gears in it....unless I can find a something already built with an aftermarket LSD (and cheap, like a NISMO))

Note: I just do time trials and HPDE Solo stuff, nothing big.

Originally Posted by Fluid1

laze1- Quaife ATB LSD and the 4.09 gears are exactly what you need.

The quaife, unlike all others, has what many call "yaw control"

PM me for more info if you don't just trust me.

I'm going the 3.9 route

[Fluid1]

I'd be watching the classifieds for someone selling a full one with a gear swap already done. If you're not confident with that install, it's not cheap.

[nlzmo400r]

there should be no excess heat with the shorter final drive ratio. Apparently the backlash wasnt set correctly and the diff was set too tight and overheated. S2000s for instance use 4.77 or 5.01 final drives often, and theres no 'melting of seals', its all dependant on how the car is built.

[Axelerate]

I have the 3.9 gears and I had other 350z drivers ask me what kind of FI kit I had after passing them on the straights.

I shift more now, but I'm always in the power band. It also allows me to shift sooner on some places where I was running out of gear before, but didn't want to shift in the turn.

No overheating issues with my gears, Cusco LSD and Motul diff fluid (best I've used).

[mpowers]

Please do note that you guys are not running 3hr enduro's with 140 degree track surface temps. The diff only hold 1 1/2 quarts of fluid so throw that into a real racing scenario and tell me how it turns out. Just passing on my experience with running the gears....fwiw when we rebuilt a stock diff the seals already had signs of deterioration from heat from the events.


edit: it took an hour -n- twenty minutes of racing to bring the temp up enough to melt them...

[laze1]

Yep, that is the plan..buy a complete unit that already has the gears and the diff (even a stock VLSD) to replace my stock unit. I will keep my stock unit for a spare and/or for when I sell the car...

Originally Posted by Fluid1

I'd be watching the classifieds for someone selling a full one with a gear swap already done. If you're not confident with that install, it's not cheap.

[Fluid1]

Originally Posted by betamotorsports

As some who's raced a number of cars (both FWD and RWD) with Quaife differentials, I am curious what you are referring to as "yaw control." I was just on the phone with Mark Ortiz regarding another subject and I asked him about the term. He's curious too. I do know of "Active Yaw Control" and that's done with electronically controlled active differentials (ECAD) and the Prelude SH was one or the first production cars to use this tech.

Does your term "yaw control" refer to the designed in torque distribution of the Quaife? If so, how does it control the yaw rate of the chassis different from a CLSD with some set lockup (80% lets say)?

I'm not challenging you, I'm just curious because I've never heard therm used with a passive differential.

Putting power down to the wheel with the most resistance....which, in a turn, is very similar to yaw control.