Ola folks, Kermee here....been a LONG time, Tranny questions Options

[degreeoff]

First off good day to all the old salts and fresh meat!

Just aquired a 902/02 tranny from a 912with the MSX gearset....YAY! (or not?) I must say that with all my track time (not much but more than a few days) I have yet to top out and have been lusting after the shorter box for some time. I do have concerns that some of you may be able to answer.

1) for you higher HP guys with this layout, do you run out of gears on the longer straights? (Summit point, VIR the Glen)

2) is it a big a PIA on highway trips as it looks on the charts? Now I am @ 3200 +(-) going good on a highway but to spin 4k....?)

Lastly anyone have a track vid out with the MSX combo I could see...I am @ 182hp at the wheels with a 7k redline......

thanks you"all!

Josh C (aka Kermee6) (IMG:style_emoticons/default/driving.gif)

[Richard Casto]

Josh,

As you asked about high RPM on the highway, so it sounds like this is a dual purpose street/track car? My gearing chart are telling me that you get the following with a 24" tire at 7K RPM

N 90 MPH
V 122 MPH
ZD 159 MPH

M 86 MPH
S 109 MPH
X 132 MPH

Lastly one option that you might consider for 5th is to flip your N third gear and use it as 5th gear...

N(f) 142 MPH

That is an easy to source (you already have it) compromise between X and ZD

If you have some favorite tracks, I am expecting that you should know what speed you are able to achieve on the long straights. Using that info you should be able to work backwards to see if you are going to run out of RPM using an X gear for 5th (and clearly having lower gears should allow you to obtain a higher top speed assuming you don't run out of RPM).

At interstate speeds (75 MPH or so) you will be turning the following RPM...

X 3990
N(f) 3690
ZD 3300 RPM

So you are going to see nearly a 700 RPM jump moving from the ZD to X. The RPM difference grows the faster you go.

My car is going to be a dual street/track car and don't plan to trailer it when going to the track. It is not finished, so I haven't quite decided what gearing to use yet. It's likely that I will use a lower 3rd and 4th such as M and S, but with a tall 5th gear (taller than X and maybe even the stock ZD) as I expect to use the car for long overnight trips. That will hurt me on long straights at track, but this is to be a compromise car.

And I agree that you need to hear directly from some others who have MSX gearing and use it both on street and direct. They can give you comments based upon real world experience.

Good luck! And let me know if you need any other help with the regearing!

Richard

[degreeoff]

Hey Richard,

thanks for getting back to me.......I wanted a Z for 5th...as it sits I can get near 130 on all tracks that I have been on with ZD I think I would exceed x with my HP......I was wondering if I could flip N....so it is doable?

[MikeSpraggi]

Josh, looks like you found a set of MSX gears in a tranny. Still haven't had a chance to look through all the gears I picked up. Let me know how the project is going.

[Richard Casto]

Hey Richard,

thanks for getting back to me.......I wanted a Z for 5th...as it sits I can get near 130 on all tracks that I have been on with ZD I think I would exceed x with my HP......I was wondering if I could flip N....so it is doable?

Josh,

I have a local friend who tracks and autocrosses his 914 (VIR, CMP) and we flipped N in his car for 5th gear. I am guessing you have already done the math, but a flipped N will give you the same ratio as a Z.

Richard

[degreeoff]

Hey Mike.....good to hear from you. Yep not as good a deal as you but a good deal nontheless....looks like I may have a winner with the M S N(f) AKA Z I like the way the graph looks and I will tell you straight up that the X would be too short and I'd run out of gear before track....but i'll hold onto it just in case.

The project is no go yet.....I'll wait untill winter and no heat driving is officially GONE. then I'll tear up some tranny's I have 3 so we shall see what lies within.......I know the current is pretty good as Mike did all the work and I was there to assist on the TBD install but hey I have been beatin on it a bit with a slight misalign of 4-5th