What fuel mileage are you getting and what is your setup?

My fuel mileage has been getting worse over the last year or so, but here is my setup:

I'm getting around 15 mpg average, 2.7L with the stock gears (3:73) 2.5" lift with 33" tires.

Would 4:10s make a difference in fuel mileage?

 

You should at least get 4.56s

 

Really? Won't my RPMs be pretty high on the highway with those?

 

I'm going to run 4.56s and that should bring me just a hair higher than stock RPMs on the highway with 33s. I have a 3.4 tho

 

http://www.rocky-road.com/calculator.html

This might help when selecting a new gear ratio.

To put into perspective, I have a 3.4l with 2.5" level and 285/75/16s and I almost always get 17-18mpg. RPMs at 70mph are exactly at 2500.

 

I just put my info in and it said 4:10s. Didn't ask for motor size though. That is the same tire size I have so I guess I don't have true 33s, but close enough.

 

I was always told if you have a smaller motor then it'll take bigger gears to make up the torque loss. But I could be wrong. I guess you'll have to find a good balance of highway RPM and MPG around town.

 

Yea exactly. I've been told by a couple people that 4.10s are the way to go for 33s on this truck for moderate every day driving, but I wanted to get a couple of opinions before I decide on buying gears.

 

Use the tire calculator.

Gears are expensive. If you know how to use a spreadsheet, and you are making choices based on MPG, you better calculate an ROI.

You might not keep the truck long enough for a payback. That of course assumes you improve MPG. Which is quite unlikely when going to deeper gears.

 

1996 4x4 5spd stick height 2010 prerunner take offs for wheels. 26-28mpg on the road about 20 mpg in town

 

Yea I know they are expensive for the whole set, but can't I get away with just changing the gear and pinion? Another reason for wanting to change these out is to get a little more umph out of the truck. Its a true TURD.

 

2.7l xtra cab
4x4
5spd,
3" lift
265/70/16 tires
fiberglass cap

Before I lifted, I was averaging about 20mpg city/highway combined. Since I lifted, my city has dropped from about 18mpg to 14-15mpg, and the highway (70mph+) is 18-19mpg. The biggest difference I've noticed is when the highway is clogged and everyone is only moving at 50-60mph, if I keep my RPMs around 2500 in 4th gear, and don't mash the gas, I get like 28mpg. I averaged nearly 30mpg yesterday on the highway over a 50 mile commute. I have a ScanguageII that I use to monitor fuel economy.

Not sure what my current gear ratio is- can someone point me to where I can find that out?

 

This isn't a simple DIY. Who is going to set them up for you, and how much will they charge?

You do know you need to do both axles, right?

Gears don't do a thing to the motor. All they do is change how fast the motor winds up. You lost your umph with a jumbo wheel package. Which BTW, is because you are running at lower RPM. Meaning your MPG should have improved on the road. Have you compensated your calculations for the speedo/odo error you induced?

So the consideration is do you really need the wheels and tires? Or just want them? Do you really need more umph, or just want it?

If you need big rubber functionally, then big gears are the expensive compensation you pay.

Every choice made on modifications compromises something else. So it's good to choose carefully.

 

When you find out here, reduce it the same % as your tire size increased over stock for the true final ratio.

And if your speedo/odo have not been corrected, your SCII is also wrong, as is your MPG.

 

Your stock tires WERE 29's, so going to 33's clobbered your mileage, performance, and threw your odometer way off (it now UNDER-READS).

Hard to believe you have 3.73 gears. Are you certain of that? I have stock 4.56 gears with my 2.7.
How, exactly, do you measure your gas mileage, with your odo being so inaccurate?
Have you done a tuneup recently?

 

My tires are stock size though

 

OK, missed that. So your loss was due to lift and weight. You can find your gear in the link I gave you above.

 

My odometer was corrected years ago when the lift and tires were installed by the previous owner, yes I know I need to do the front and rear end gears. I have a friend that is a mechanic and knows how to install gears. He told me I need to purchase the install kit that comes with the new seals and washers and blueing compound to check correct lash and contact after they are in. I read the manual that came with my truck and it said it has 3.73 gears. Im going to double check the passenger door jam to verify what gears are in my truck now.