What gears, tire size and fuel type are you guys runnin?

[FellowTraveler]

I've found I can go with less gears under all conditions with my K2500 diesel Suburban provided I stay with tire diameter at or close to stock because of low rpm torque output of my 6.5td.

I'm interested in results from others who have made gear/tire changes and what results good/bad then type of power gas/diesel/other.

[Metcalf]

I probably run the oddest combo.

1992 dodge with the Cummins and 5spd manual. 3.54 gears and 38.5" tires that measure out pretty tall ( 38"+ on truck at 50psi ). The truck consistantly gets 19-21mpg. I have some documentation in my thread of this. It high geared enough that I use 4th and 5th on the highway. 5th is generally for 65mph+ only. I start in 1st gear also. Overall its a combo that shouldn't have worked but was free to try. Off road is still just fine with massive torque of the Cummins.

[98dango]

I have run every thing from 2.73 and 35s to 5.29s and 31s. gearing in your diffs dose not make a huge differance once your there lol. I but keeping your rig in the sweet spot is a hard quest. Knowing what rpm your motor likes best and what it takes to get it there the easyest.

[blakeape]

I have a 1997 Dodge with a 5spd, 4.10's, 37 inch MTR's and a pretty healthy but reasonable Cummins that just put down 339HP/791Torque at the rear wheels. I tow with it a lot and usually get 12-14 mpg towing and 16-17 empty. I did get 19.5 mpg on a road trip last spring where I didn't really go over 65 mph and tried to keep the boost below 20psi. I am pretty happy with it.

[Rovertrader]

'11 F250, 3.55s, 37's and 21+mpg on trips at 65-68, and 16-17 mpg around town. 400hp/800ft#- awesome!! and warranted...
'07 Dodge PW, 4.56s w/37s and 12 mpg on trips at or below 65, and single digits around town. 400hp/425ft#??
above are actual and corrected for tire size

[chasespeed]

01 Ram w/ a well done 12v Cummins(YES, it was swapped in, and I almost wanna knock it back a few notches) 5spd, 3.55s, and 35s... avg 19mpg. I do tow, and work the truck. If I keep my EGTs below 600*, my mileage is great... I have seen 22+ on LONG highway trips...

Anyone want a Cummins? I know where you can get on....

Chase

[bfdiesel]

I have a 6.2 with 4.10's and I run a 33" tire. It does dog going up the mountains or steep hills, but does reasonably well considering it is a 140 horse @ sea level naturally aspirated diesel. Mileage is good 15+ with no overdrive on biodiesel.

[goin camping]

8.1 w/ 3.73 gears and a 32 in tall tire. Gets 13 and a bit Hwy.

[lstzephyr]

I have a 91 dodge with 32s and 4.10s. Its a 12v that is only slightly turned up to probably around 200hp. I get 25 on the highway and 20 ish around town. I rarely go faster than 65 and I keep the boost low.

I like low gearing. My bike tops out around 90 and the truck tops out around 80. I usually don't have either above 65 and very rarely above 70. Keeps me out of trouble.

[1stDeuce]

My '96 GMC with the 6.5L TD and a 5-speed got 20-21 (corrected odo) with 3.73 gears and 235/85's at 68-70. 245's took it down to 18-19 at the same speed, as did going to 275/70R17's. All Goodyear ATS's. Little better towing and braking with the 245's, little better ride with the 275's, but the 235/85's were by far the best tire for that truck for doing it all!
YMMV.
C

[greengreer]

Agree on the 235/85's!
Just got goodyear duratracs in that size on my '98 K2500 6.5td 5-spd with 3.73. Perfect size for the truck, although i would love to try 255/85/16

Get between 15-19mpg depending on what I am doing

[Code Monkey]

'97 Dodge 3500 4x4 w/ 12' flatbed
Cummins diesel
5 Speed manual 0.7 overdrive in fifth.
4.10 diffs
27" tall tires on 16" wheels
I haven't got an exact number on fuel yet, but I think it is close to 15 MPG.

At 60 MPH indicated it is about 2300 RPM, which IMO is way too high - because of the gearing and stock tires/wheels. It tops out at just below 80 MPH indicated.

My plan is to go to 19.5" wheels and 35" tires, which I calculate will give me 71 MPH at 2000 RPM and less at 65 MPH, which should significantly improve the mileage on the highway.