So, the road race car, has an F23 transmission in it with the 3.84 Final Drive. Would it be worth swapping the gears from an XFE (Final Drive 3.63) Into it to try and help the car at the track? Looking to try and get more MPH out of her. Top Speed is only really an issue at Fontana and Willow Springs, but would like to run faster at Buttonwillow to.

Or am I looking at this totally backwards?

 

well, if your running out of gear then yes, swapping to the xfe 3.63 trans would help.

are you really hitting the rev limiter in 5th gear though?

 

Hitting the limiter in 4th at Fontana. 5th didnt really seem to do anything

 

I have something that will be of use to you. pm me your email address and I will send it to you

 

what do you mean? did the car just not pull anymore, or the rpm didnt drop much? and you have removed the speed limiter in the pcm right?

to me if your only using 4 gears id be going the other way with the ratio, id be trying to put an f35 in with a 4.05 or 4.45. ideally on the longest straight you run on you should be just hitting the limiter in high gear just before you brake.

 

Yes, speed limiter is gone. And car hit 116mph thru 1 and 2 in 4th. went to 5th, and it dropped RPM but didnt really keep gaining speed.

 

I'm running the F35 4.45 and I don't have to use 5th gear at my local track. It's not a super long straight but I'm right around 7,000rpm in 4th gear at ~140mph.

 

my 4th gear is 144 at 8k haha. 126mph at 7k

 

what size tires are you running? my math says 4.45 f35 should be around 130 at 7k

 

that tells me your out of horsepower for the gear ratio. going steeper (numerically lower) will make the car slower.

swapping to a numerically higher final drive will help the car out of the corners and allow you to use 5th gear. another option would be swapping 5th gear so its not as steep. iirc the saturn vue with 2.2l used the f23 and a shorter final drive ratio, however im not sure what it is. i think all f23s use the same 1-5th gear ratios, so a factory 5th gear swap isnt an option, would have to be something custom.

another option is to make more power. im not familiar with your engine setup (i know its n/a) however you might consider doing some things to move the power curve up. imo, stiffer valve springs are a must, if the engine is stock id bet those springs are bagged by this point. ive seen as much as 30 whp gains on a mild ls engines just by changing valve springs. consider a balance shaft delete, even some different cams. if you can raise the max rpm you can push the car a little farther in 4th gear, and if you can make more power higher up you may be able to pull the 5th gear thats in it.

 

i did some looking on the f23 gear ratios, looks like you actually have some choices.

final drive
cavalier/sunfire/grand am/alero- 3.94
cobalt/g5/pursuit/ion- 3.84
cobalt xfe- 3.63
05-08 hhr- 4.17
09-11 hhr- 3.95
04-07 saturn vue- 4.41

all the 1-4 ratios are the same (3.58, 2.02, 1.35, .98). there are in fact 2 5th gear ratios, all but the saturn vue run a .69 5th gear, the saturn vue uses a .81 5th gear.

its possible all your troubles could be fixed by putting the .81 5th gear in. .69 is a hell of a steep ratio to pull, it doesnt surprise me that it just wont pull in 5th.

for a race car, id be sticking that .81 5th into it no matter what you do. i cant see ever needing a .69 5th gear, and the 4th to 5th jump will be a lot less. i would however spend a bunch of time with a gear ratio calculator. figure out your target top speed and select a final drive ratio based on that.

 

a full vue trans would probably actually kick ass at the track since 5th would actually be useful.

For a car with any torque 5th is slip city for the clutch because its quite the jump from .98 to .69

 

i actually ran the numbers, the vue trans would still give a theoretical top speed of 140mph at 7000rpm on a 24" tire. imo you cant get any better than that.

for the record, theoretical top speed on a typical cobalt f23 was 202mph.

 

Very useful post

(Had to comment so I could easily find this thread later if needed)

 

That info is definitely out there. Nobody ***** with the f23 anymore so not many are aware of the options. Id like a 4.17 for myself.

 

You might be right, was doing this from memory. RPMs could have been a bit higher. I run stock size tires.