jtlucas

Is a 3.55 ratio decent for MPG? I was told this can have a big impact on what mpg results are.

Thank you!

4leggedbucket

Right in the middle...373s are better to tow or big tires and the 331s would be better for fuel econmey but if it' behind a 10 speed it prob don't make that much of a difference imo

jtlucas

Great! It is behind a 10 speed so I'm glad to hear that. Thank you!

sierrafast

The difference between 3.31 and 3.55 is almost insignificant. Both would be good for mpg with stock tire height if you don't plan on doing some heavy towing.

BTW, I went from 3.23 to 3.73 on a previous GM truck I had and actually got better mpg on a 50/50 mixture of hwy/city driving.

Don't be afraid of the 3.55 or even the 3.73 rear ends.

donk_316

I have 3.55 rear gears with the 3.5EB and 10 speed.
Lifted 6" and on 35" tires

Averaging 17L/100km which is around 14mpg in 10,000kms (6,000m)

johnday in BFE

iTrader: (1)

The 3:55 and the 10 speed is a great combination. With that trans and gear, in the lower gears you are actually around that 3:73, in the higher gears, you're close to the 3:31. That's in comparison to the 6 speed.
I'm running a 93PRX tune, and on a 200 mile trip, 120 miles at 75+, and another 80 at 65, I'm at 19.3-19.7 on the lie-o-meter. That's all on winter blend gas. I haven't had any summer blend in it yet.
There's a chart floating around here somewhere that can verify those gear ratios. I'll "try" to find it.

jtlucas

That's great! Thank you Johnday!

johnday in BFE

iTrader: (1)

No problem at all. I might point out that mine is also the 3.5 Ego.

Re-tired

I had a 1998 Dodge 2500 with 3:55's & cummins 12V and got 21mpg avg.
Then I sold it and got a 2003 Dodge 2500 with 4:10 and 24V cummins and got 17mpg avg.

Pretty big difference- but not very noticeable in towing power- I was suprised

zx12-iowa

3.31 is a highway gear and often produces worse mpg unless you baby it. 3.55 I find is the best blend of performance, towing and economy...