4.56 vs. 4.88

[Thurlo76]

i have an 87' 4runner, brand new rebuilt 22re, 33x12.5x15's, and 4.56's. my last tank i got 24.4 mpg. i also have a set of 4.88's sitting out in my back yard. they came off a 94' parts truck. anyways i have read alot on here and the ideal gearing for 33's is 4.88's, if i swap out my 4.56's with the 4.88's will i get better mpg's? i know ill get more power just cuz they are lower. i didnt know if the big hype about 4.88's is worth swapping them in or not...

i do more city driving than anything else. not more than about 50 miles or so at a time. any advice would be appriciated.

 

[Hyde802]

If you do end up swapping them....wanna sell me your 4.56 front diff? Mine just crapped the bed. haha.

 

[Thurlo76]

if i end up swapping them i would love to, but still not sure yet. no one has looked at this post. o ya i have a 5 speed if anyone does end up looking at this.

 

[fourwd1]

With a 5 spd manual trans and 33" tires, 4.88 gears will get you closest to the optimal power band. 4.56 and 31's the same.

 

[fourwd1]

Also, the difference between the two ratios would not be enough to justify the cost of regearing your diffs, but since you already have have 4.88 diffs lying around, it would be worth it.

 

[Thurlo76]

im not to much worried about the power band, just lookin to get the best mpg's. i think i might just swap in the rear and see how the mpgs go....

 

[Hyde802]

Thats probably your best bet. If you like it do the front, if not put the 4.56 back in.

 

[2gen4runner]

If you look on google you could probably find a chart that tells you tire size and the write gearing for it......and if you find a really really good chart it will tell when your cruzing down the road at 55mph what rpms your at in 4th gear or O/D off with your gears know and then with 4.88's.......this is for optimal mpg

ill try to find a chart for you

 

[2gen4runner]

ill try to find a chart for you

http://nationaldrivetrain.com/art_information/ApplicationChart.gif



Hope this helps

 

[fourwd1]

im not to much worried about the power band, just lookin to get the best mpg's. i think i might just swap in the rear and see how the mpgs go....

An engine operates at it's best both power and mpg when it operates in it's designed power band, so maybe you should be

 

[snw4runner]

This is a noob question but, how do you read the chart? I mean other than matching up the gearing ratio to tire diameter, how do you know where your optimum gearing ratio to tire diameter should be? Is it highlighted in yellow, red, or white? Sorry for the dumb questions. Thanks