changing gears, maybe///

[Gerry A.]

I am seriously considering changing the rear end gears in "Lady Vox" from 3.0 to something a bit more "radical." She lugs quite a bit in the lower gears unless you are constantly on the gas. Not that I don't really love the mileage I get in 5th with the final ration at .68 and the RPM at around 1500 doing freeway speeds but I'm looking for a bit more snap. Would like to go with maybe 3.89's or 4.11's not sure which but want to keep the RPM between 2500 and 3k at say 75 or 80, I never was very good at math.(LOL) If any of you have a 28 spline pig for a 9" Ford rear that you just have to get rid of in that range let me know how much and I'll try to sell my first born (just kidding...hahaa). Seriously though I am looking for something and thought this might be a good source to try first. Also let me know if I'm in the ballpark on the ratio.. Like I said I don't want to destroy the drivability as we do alot of cruising but I still want to be competetive in a testosterone contest if I get the urge..if you know what I mean..I may also want to try a few weekend races in the near future just for the heck of it.. I did used to race go-karts in my younger days.. I miss the 167mph with your butt 1 inch off the ground and your head between two screaming mac 91-b-1's turning 21,500per. Quite exilerating!!!! Anyway take care and let me know any info on this.. Thanks.

[Clois Harlan]

Go to this site; you will have to register but it is free and only takes 2 mins. Based on what you posted I think you may want 3.73 : 1 gears.

http://www.smokemup.com/auto_math/mph_range2.php

[Gerry A.]

Thanks will give it a try and see what happens.. like I said I'm pretty sure I want to do this but not 100 percent..

[John 550]

I went from 331 ( great 2nd) to 354 .
Very happy . 3100 rpm @70 . 4speed top loader .
I lose some top end though

[Gerry A.]

Now I'm somewhat confused, I went to the site you recommended Clois and here's what I discovered. If I go with 3.89's I'll be running freeway speed (right around 70) at just a touch under 2500, it worked up to 73mph at 2500. If I go with the 4.11's I'll be running the same speed at approx. 2700 or so really not much difference. I did discover something very interesting however.. I did the calculations assuming I did not know the rear end ratio I had and going by the RPM vs. speed to give me my final ratio it showed something I wasn't expecting. I know by observation that I run 60 on the speedo at 2000 RPM showing on the tack in 4th.. I've done it a hundred times so common sense would say that if in fact 4th is 1:1, which it is, my rear end ration should be 3.00. 2x3=6, or so I thought.. maybe it has something to do with the tire dia. which it also asked for because it said that my rear end ratio was 2.563:1. Did I do something wrong? When I was doing the math awhile ago trying to figure things out I kept comming up about 9 mph different than it should have been mathematically and you know what?
When I plugged in 51mph instead of 60 and used 2000 rpm as the reference it said my rear end ration was 3.015...now is that coincidence or what? 9mph difference and the ratio comes up so close to 3.0 it isn't funny yet logic would tell you that at 60 if 2000rpm is showing on the tach then the ratio should be 3.0. This is getting silly. More and more I'm thinking I should just leave things alone but I can't help but feel that 3.0 is a bit tall when it comes to performance even if I do lose a small bit of drivability.. according to the charts I won't lose that much either way I go 3.89 or 4.11 but I'm leaning toward the lower one just to be on the safe side. besides the 4.11's are almost 100.00 more. Guess it's because they are more popular. What is the census poll on this one? Thanks for the site though I think it provides alot of good info in lots of areas.. I have it in my favorites now and will use it from time to time.

[James Neal]

Tire size is an important factor in final drive ratio, is your speedo accurate? Tire size is the easiest and fastest item to change to adjust your final drive ratio up or down on tire size can effect your topend speed and bottom end launch,we use to carry three sets of rear Wheels 33", 34.5" and 36" depending on how we wanted to launch or mile an hour. 33" would get you mile an hour, 36" would get you Good 60' but your mile an hour would be less. This was one of the easy things you could adjust for track conditions, teamed up with trans gearsets and rear gearsets we could minutely adjust for each track. I think you would be happy with a 3.50 series gear, the 3.89 and 4.11 are great for street terror but you allready probably have a slight traction problem as it is, to really nail em' you need some cheater slicks,Drag radials. 3.50 gears are still great for the long hauls,3.89 and above are annoying for the long ones.The most practical solution is two carriers if its 9" they don't take long to change.Used 9" carriers are cheap on E-bay w/gears freshen up and go. Have Fun
Jim

[Clois Harlan]

Gerry,

Sorry not to get back to you on this but I have been at Road America in Wisconsin since last week. If you still need some questions please ask again and I will try and answer them for you.

Here is what I do to calculate my desired gears:
1. measure my rear wheel diameter which is 26.5 inches
2. plug in my transmission from the choices given in the
drop down box menu.
3. I put in the gears I am thinking about running eg: 3.73
or 3.54.

The table will show me at what RPM my mph will be. I know my
desired top RPM will be no more than 6500 rpm. From this I can determine how fast I can expect my top end to be in each gear.

Clois

[Anthony]

Change the tranny, instead of the gears. Keep the 3.00 rear gears, and change to a richmond 5 speed, or a g-force 5 speed with gears similar to the richmond. You'll have a true close ratio 5 speed, and not a wide ratio 4 speed with overdrive that you have now. The TKO is a good tranny, I just don't think the gear ratio's are optimal for a cobra, a light car with a high hp engine. The gear ratio speads are too wide.