I have a Roush P51 A (TVS 2300 w_forged bottom end)and wanted to know what gear wold you guys recommend. I was thinking of 3.73. Also how high would the rpms get at around 70mph in 5th gear. I have also heard that in supercharged cars with 3.73 gear the first gear is useless. the car is used as daily driver and a weekend track days(road course only, no auto x and drag). Any would would be appreciated.

 

3.73 is a good all around gear, that is what i am going to go with and i am planning on buying the P51 engine from roush with the supercharger. Right now i have 3.31s and they are ok but 3.73s are better, but you would think Roush would add something better than the 3.55s on the car that came from the factory.

 

go 4.10's, and look into a transmission upgrade!

 

I'd just keep the 3.55s and this is coming from someone with a TVS and 530 rwhp..

 

+1 on the 3.55s. Buddy of mine retrofitted the P51 engine to his Roush Track Pack...he is now removing the 3.73s he previously installed after a few race weekends w/ the new engine, and going back to 3.55s.

 

what about the lsd, i was thinking getting the eaton Tru-Trac.

 

Tru-Trac would be a great mod. I'd recommend you go check out fnsweet.com, it's a Roush forum.

 

I like my 3.73's (N/A). It feels strong and torquey without over revving.

Unforunately, I didn't note the rpm's at 70 but as I remember its about 22/2300 rpm in 5th. (and its just gone storage for the winter )

But I did note that:
1st redlines (6500) at 40,
2nd @ 65,
3rd @ 105,
4th @ 120ish, and uh.....
5th @ 125... is cruisin' fine... @ 3800 rpm.

 

WISDOM

 

I have 3.73's and usually stay at 70mph and the rpm's are a little over 2k.

 

I'd listen to this man.

As for first gear being useless, it all depends on the density of your foot.

 

I'd say 3.55s

3.73s are just a little too much for my taste


also.... or

 

I'm flattered.

First gear isn't useless on drag radials or slicks though!

 

I've gotta agree with NastyStang too.

I just don't see the trouble and the money from going to 3.73's to even be worth it.

I had 3.31's when I was NA and wanted 3.73's. I drove a another s197 with 3.73's and just didn't feel enough of a difference so I went wild and got 4.10's.

Stick with the 3.55's.

 

RPM depends on what tire size you are running.

 

I have 4.10s - RPMs are about 2,200 at 70mph