Should I go to 3:90's or 4:10's with 28" tire

[Jivepepper]

If I go from a 26" to a 28" rear tire and an auto, should I also consider switching out the 3:73's for a little steeper gear?

[Rodeheaver's]

give it a try first.. but the 373s sound to be more suited for your car..

[biminiLX]

I base the rear gear on where you want the rpm going through the traps.
Look at some of the online calculators and you will have to guess converter slip also.
-J

[Jivepepper]

I base the rear gear on where you want the rpm going through the traps.
Look at some of the online calculators and you will have to guess converter slip also.
-J

A guy gave a link that has a calc for conv slip too.
http://www.tciauto.com/Products/TechInfo/Calculators.asp#4

According to those calculators.

If I run 3.73's with 28" tires, a 1.1 trans ratio in drive, with a converter slip of -0.0106%, Which I deterimined using the calculator for determing converter slip. I will be going 130 at 6400 rpm? Does this sound correct?

What's weird to me is that is says at 6500 I would only be going 128, with all the other varibles being the same except the converter slip goes to 1.55171% at 6500rpm. Could only 100 more rpm make such a huge difference in converter slip, causing the MPH to lower?

I think I might have did something wrong.

Here's a pic of the calculators

First pic shows calcs for converter slip and mph @ 6400rpm


Second Pic pic shows calcs for converter slip and mph @ 6500rpm

[Shorty429]

I would go 4.10's. a friend of mine had 3.73's in his 06GT auto and when he put the 4.10's in it ran a lot better than with 3.73's. 4.10's FTW in an auto!

[Jivepepper]

I would go 4.10's. a friend of mine had 3.73's in his 06GT auto and when he put the 4.10's in it ran a lot better than with 3.73's. 4.10's FTW in an auto!

I think it has a lot to do with how much power you're making also. I don't want to exceed 6500 in drive when I go through traps at the track.