i am currently running 35s with 3.55 and im getting about 7.5 around town and thats because i have a heave foot... normal driving is around 8 mpg... highway goes up only a little bit but only like 1 or 2 if your lucky because higher truck= more air that needs to be pushed... i have 4.56 gears but no money to have them instaled

 

TurboABA, just because you saw ok gas mileage, doesn't mean that 3.55's and 35's is a good idea. I didn't have the same results as you at all. Maybe it's that my truck is an extended cab (so heavier), or that i'm runnning mud terrains (more rolling resistance), but my mileage was terrible when I put the 35's on, and I also couldn't keep the truck from coming out of OD. The smallest hill, or even a stong head wind, it would downshift just trying to maintain RPM. And I had 4.10 gears at the time. All that went away when i went to 4.56 though. Mileage went up, and power is as good as it has ever been, even with big mud tires.

 

You can kill your transmission even with stock tires. It's all in how you drive it and service it. I've got 181xxx on the clock. The 35s with stock gearing are not putting any more stress on the tranny then an average trailer with some seadoos or a boat would.

As long as I don't shock the transmission with burnouts, drag racing or hardcore rock climbing, it's not going to work much harder then it would pulling an average trailer on stock tires.

 

Yes, I will agree with the fact that it takes a different driving style. You basically have to keep momentum up just like you would while driving a big semi, or pulling a heavy trailer. Just like you mentioned above, I go out of OD and even have the transmission downshift when the load gets too great but unless you tow a lot or constantly drive through the mountains at freeway speeds, it's not the end of the world.

I'm not sure of the condition of your truck when you got your results, but in order to get this kind of milage, I had to run the tires at MAX infation pressure. I'm also running AMSOIL fluids in both diffs, transfer and transmission. I will try to get some around town MPG readings, but I can assure you that they will be under 10 MPG most likely.

The 35s have effectively dropped my gearing to 3.24
To get back up to the original gearing, I would need to change to a 3.90 gear set.

Since you went up to 4.56s you truck should perform just as it would with 4.16s (if that ratio was available) and stock tires, so I can completly understand why you've got lots of power.

Bottom line is, I can deal with the lack of power for my application, simply because I've adjusted my driving style, and mainly because unlike most people on this forum, I'm not trying to get acceleration performance or run the 1320 in a vehicle that's built for other purposes.

But then again, that's my personal opinion, and we are all entitled to our own, so I appreciate the suggestions. I may consider changing my gear ratio in the future if my needs change.

Peace!

 

I've almost completely blown my full tank by doing only daily driving, so I will have new MPG numbers tomorrow when I do a fill up. Surprisingly, I don't think the numbers will be as low as I had previously expected.

 

Just filled up and re-calculated. Ended up getting 12.56 MPG.

 

I did mine this weekend i have 255/70/16 got 13 doing 75 on the way up to the other house and 9.8 on the way home i was doing 80 at 3:30am. It was sweet on one on the road at all.