Older Truck Gearing

trucks
gasoline
gmc
2500
fuel-economy

#1

My wife and I have a 1981 GMC ? ton pickup with a 454 cubic inch big block engine. We really like the big block because about twice a month our horse, Bourbon, is hauled around to dressage shows where my wife and he competes; and it?s really nice to have the power that the 454 provides. But, what?s not so great is the roughly 11 miles per gallon mileage needed to get from point A to point B!



I?ve been told that today?s trucks are geared differently than the ones produced in the early 80?-thus get better gas mileage. I find this highly believable because the truck has a 3 speed transmission with granny gear, a 4-11 rear end (so I?ve been told), and cruises down the highway at 3000 RPM while going 60 mph. Going faster just causes the engine to rev at higher speeds thereby putting out much more horse power than needed to sustain constant speed on level ground. It?s as though the transmission needs an overdrive.



So, my question is: Given today?s technology/market, do you know of a transmission and rear end combination that is better suited for our GMC?



Thanks!


#2

I don’t know about gearing on a 2010, but if you’re wanting better than 11 mpg while pulling a horse and trailer with a gasoline-engined pickup, you’ll probably be disappointed. You can certainly get one that’ll be better when not pulling a trailer, but once you put on the trailer I bet you’ll be back into the 11-13 mpg range unless you go for a diesel. If this twice a month job is most of what you use the GMC for, I can’t imagine saving enough money to justify replacing it.


#3

Your truck suits your purpose exactly and with OK mileage. Unless you want to spend thousands to save hundreds,you are fine.

Now that being said, if the motivation to change things is a desire to use less fuel because usuing less fuel looks better to your club (and this is OK)Start with a simple reduction in rear end ratio (next stop is 3.73 I believe).Expect to gain 1.5mpg if you stay below 60.

Do not tow over 60mph unless your entire rig has been examined by a pro and given the green light, then still dont tow over 60mph.


#4

I don’t think I could say it better than oldschool’s words:

“Unless you want to spend thousands to save hundreds,you are fine.”


#5

The 2005 V10 F-350 that I used as my demo when I was selling Fords a a 4.30 rear end, it also got around 8-12 MPG. Most 3/4-1 ton trucks today have 3.74-4.10 rear end ratios, the same as have had for 30 years. However all newer trucks have 5 or 6 speed transmissions with one or two overdrive gears that help eek out an MPG or two in highway driving.

If you’re getting 11 MPG out of a 454 with no overdrive and 4.11 gears you are doing very well. And there’s nothing cost effective you can do to increase the mileage significantly that you see a return on in fuel cost savings.


#6

I’ve pulled horse trailers and you have the perfect truck for the job. If you had a truck with a 5 or 6 speed transmission, you probably would have to use the lower gears anyway. If the gearing is too high, your horse Bourbon will probably have to pull the truck rather than the truck pulling Bourbon’s trailer.