Need opinions: 4.56's or 4.88's

Where exactly are you getting those numbers from?

Using grimmjeeps calculator I came up with this which is not exactly even close to what you said.

 

Seems kinda inaccurate. I monitored my rpm coming home tonight. At 70 I'm at 2800. I have 35s with 4.88s

 

Possible the tranny is different? What kind of gas milage are you getting?

 

Oh sorry I actually calculated with the manual tranny which has a really shitty 6th gear ratio. Automatic will be better.

 

Most of your gas loss is when you accelerate and decelerate. Larger tires and our stock gears means the engine has to put out more. Lower gearing will help in the MPG department.

 

12-13 city, 15-16 highway

 

You aren't going to get much of your milage loss back. When you were calculating your milage were you compensating for the difference in tire size?

A 35 is almost 13% larger than the stock tire so when you calculate your MPG you should be adding 13% to your odometer reading. If you weren't doing that, you were actually getting better milage than you were calculating and when you re-gear you may calculate better milage when you aren't actually getting better milage

 

You are correct I forgot to take that into account. But taking it into account:

Stock size circumference is 96.13.
My 35's circumference is 110.0 inches.

110.0/96.13 = 1.14428

Or 14.4% larger. Meaning 12 mpg is 13.7 mpg.

I still lost a bit over 4 mpg.

So doing the gears won't really restore much mpg, but will get my power back. My best bet for gaining milage back, im assuming, would be to finish my intake system with the TRD intake I want, the URD MAF and a throttle body spacer. Although it prolly will only get me another 1.5-2 mpg is my guess.

 

This will not do anything according to everything that I have read.

 

4.88s for 37s.

 

So on my old truck with 4.56 and 31's I was getting about 515km per tank. I put on 32's and according to what is being said here my mileage should be better even if it reads slightly worse? I was getting 450km per tank babying it once I put on the 32's. That's all highway, I filled my truck more often and used more fuel. I know for a fact because I commute everyday an hour. Even did a tune up and a drop in K&N, 2.25 exhaust and still no improvement.

Maybe putting taller skinny tires with the same rolling resistance as the stock ones will give you better mileage on a prairie road but in real life what I've noticed is the less hard the engine has to work the less fuel it uses. In my older Toyota's and my friend's we went from 4.10's to 4.56's and noticed an improvement in mileage running 33's, we also found we didn't have to have our foot as far into the pedal as with the 4.10's.

I'm not saying get 5.29's with 33's and you'll have great mileage, but I disagree with people thinking running 3.73 with big tires will get better mileage than re-gearing. There is a happy medium, your truck doesn't wanna work hard turning tires, especially if there was hills on your highways. There's times I drop down to 4th gear and barely have my foot in it for hills, which in my opinion is better than being in 5th and almost floored even though the RPM's are lower in 5th.

 

I agree with you here. Which is also a reason I think it is important to have any type of MT road forced and the tire spun on the wheel if the road force is really bad. While this may help with some vibrations, less force on the road may be able to help with mileage. By no means would it be very noticeable but it should be help some.

 

I don't think anyone here is saying bigger tires should give you better mpg. Taller, wider, heavier tires increase the rolling resistance and increase the aerodynamic load. Bigger tires almost always give worse mpg. Tire model can make a big difference too, size isn't the only thing, my stock Firestones gave me 3-4 mpg better than the same size Michelins I regretfully bought.

I don't find the same results as you on hills though, any time I downshift from high load, low rpm to lower load, higher rpm my scangauge says my mpg just got worse.

I'm glad you proved to yourself that a K&N and exhaust didn't improve your mpg, they don't.