Has anyone done a gear swap on these trucks. I figure the purchase of a programmer (any suggestions) a smaller gear and going from the 225 70 to the 245 70 tires and would accomplish some sort of fuel mileage increase. Anyone been experimenting yet. And if so part #'s would be great.

I did a gear swap on a Bluebird All American Bus with a 3208 Cat went from a 5:29 to a 3:66. Top speed went from 55 mph to 72 mph. and in the mountains it actually climbs better. Allison transmission just downshifts to a lower gear and it hauls butt. Now the best part is my fuel mileage went from 5 mpg at 55 mph to 7 mpg at 68 mph. Life could not get any better. I just bought a C4500 Crewcab and am going to change it. Current is a 4:44 think I will try a 3:6x as I want better mileage.

" I just bought a C4500 Crewcab and am going to change it. Current is a 4:44 think I will try a 3:6x as I want better mileage. "


Thomas,what will you have to do to compensate for the speedo change after the grear swap?

3.73 is the highest you can go with the S110L axle. Go to: www2.dana.com/pdf/AXIP-0054.PDF for more info. IIRC, somewhere I read that GM can be reprogammed down to the 4.10 rear end.

Luckly; I do not have that axle but rather a S135-S. The gear ratios for it go from 2.81 all the way to 7.17. See www2.dana.com/pdf/axip-8941.pdf. Hope this is helping. Thomas

I have the 06 c5500 with the 5 spd allison auto I am not to sure which gear is in it and would like any info on identification. I have seen on the programmers that they can compensate for the swap with speedo. Also I do a large amount of work with a chevy dealer (not medium duty) they have the tech 2's to reprogram it. I would like something in the low 4.10's

There is a tag on the carrier that has the ratio listed.