View Full Version : Gear Ratios

Chuck Richard
10-31-2008, 10:56 AM
Hello All,
I have a question that has been bugging me for some time. I have a '01 Chevy K2500HD 8.1L with 373 gears. I wish I had a diesel now that I have upgraded from a 24'TT to my 3055RL Bighorn but this truck is paid for and I do not want a new payment. My tow rating is 13300 with the 373's and jumps to 15300 with 410's (trailer life tow rates from Heartland link). I know the common logic is the lower gears would be worse for milage and I agree when not towing. What I do not know is because there would be less strain on the motor would I actually be able to let up on the gas some and get better mileage (towing) if I did the gear swap? It works OK as set up but the extra performance would be great if it did not kill me at the pump. Anyone out there been through this or have a similar truck with the 410 gears and can give me their mileage? I get as low as 6mpg in the hills and up to 7.5 on the interstate.

10-31-2008, 11:42 AM
I don't believe there would be less strain on the motor...the engine with 4:10s has to turn more RPMs to maintain the same speed as the engine with 3:73s (on level ground, anyway).

The 4:10s get the sitting dead weight of truck & trailer moving with less strain on the engine & transmission. In hilly areas, the nod would go to the lower ratio rear, also.

IMO you have to determine, #1 how much time you will spend towing vs. running around town & #2 where you will do most of your towing, flat or hills.

Another option may be an overdrive/underdrive unit such as those at Gear Vendor (http://www.gearvendors.com/) or U.S. Gear (http://www.usgear.com/dual_range.htm). May seem pricey, but cheaper than a new truck.....

Forrest Fetherolf
10-31-2008, 01:14 PM

I recommend you stay with the setup you have and drive the truck within its capabilities until you can upgrade to a diesel. Changing to a 4:10 will cost extra, will add some power when climbing hills, and decrease mileage under normal driving conditions. A Gear Vendor is a good thing to have, but the cost is over $3000 installed. Save your money for now, I don't think either option would be cost effective.

I have a Duramax now and had a Pace Arrow 34' motor home with a Gear Vendor.


Ray LeTourneau
10-31-2008, 01:24 PM
Chuck, I had the same year truck with the 8.1, Allison and 4:10's and my mileage was not much better than yours. I had some bolt on goodies that helped with the performance but they did help the non towing mileage much. I had Air Aid intake and throttle body spacer and a magnaflow cat back. The muffler only added noise to the cab especially. The best improvement was the Throttle body spacer and intake. I was able to get 13 not towing.

Chuck Richard
11-01-2008, 12:51 PM
Thanks All,

You have saved me some money. I may do some of the updates like the air box but will stick with my setup and watch for diesel deal.