After putting Hummer 315 tires on my rig, I am a little disappointed in the accelleration and city and towing fuel mileage with my CTD. I'm considering swapping out the 3.73 diff gears for 4.10's, but my buddy with the same truck (except he has a Banks six gun and LP setup running 38" tires) thinks that the money is better spent on increasing HP/torque with engine mods.

As a jeep guy, I would always improve the gear ratios before pushing more power through a less than optimal gearing setup, which strains the tranny, torque converter, etc. Going back to the stock pizza cutter tires is not an option, and I only tow a 4000 lb boat. What are your thoughts on the subject? Thanks.

 

I have been thinking along the same lines (also a jeep guy ). It would be interesting to collect MPG figures for trucks with 315s (3.73 vs 4.10). Hiway speed would be important as a guy I work with (2nd gen) gets great mpg but he drives 10 - 15 below the speed limit every place he goes. Not a good compare if MPH and type of towed load is not considered. And please only hand calculated figures (no overhead readings).

Mine: City around 15.5 - 16 MPG (not a big city/no gridlock)
Hwy @ 75-80 MPH 16.5 - 17 MPG
Towing 8K to 9K box trailer @ 75 (I know, to fast) about 9 - 9.5 MPG


Let's get some info from other 315 guys.

 

Highway usually 65-70mph: 16.5-19 mpg

City mostly stop and go: 14-16.5 mpg

Towing 10,000lb travel trailer: 13-15 mpg(Usually keep it around 60-65 mph)

This is with 315's and 3:73 rears with a 6-speed and the Edge Ez set on #2.

 

First off, Is your speedo calibrated for the tire size. This makes a huge difference in the way the truck shifts.
Second, I have the quadzilla xzillerator xzt 60hp towing module. This will solve your problem, and you'll never look back. You can buy this for well under $300.00.
I too was thinking of swapping gears, but I put this module on, and it is the cats meow.
DK

 

Dan, that's what I wanted to hear. Speedo IS properly calibrated for the BFG 315's. For me, it's more of an accelleration thing than mileage. My mileage already sucks: 11.4 city, 15.5 highway, about 13 towing on highway. Did the TSB reflash last year, too.

 

The xzt will break traction if you want it to.
I pulled out yesterday just behind an 05 6-speed that still had the advertising dealer plates. He jumped on it and wanted a little side by side comparison, I could see him grabbing gears as I walked him effortlessly. I let off at about 85, and he went flying by with a grin on his face. This module is so much for so $little.
DK