quick gear question

[cassio]

im planning on running 35's soon and i was planning on gears

i was set on 4.88 cause thats what seems to be the general rule

but sorry to seam like a mall crawler but my xj is my DD and will be for many years to come...

so when i regear it i was hoping to get the best gas milage available

if im going more towards gas milage should i go with 4.56 gears instead??

cas

[53guy]

I wouldn't. I've got 35's, 4.0L, Auto, 4.56's and I can't get better than 14.5mpg no matter what I do or how I drive. Go 4.88's, especially if you have an auto. I hear that with a manual, 4.56's are like 4.88's.

[sidriptide]

i would say you will get better fuel economy by leting the engine rev a bit.. higher (lower numerically) gears will lug the engine a little more.. higher RPM might make you assume you will use more fuel but it really has to do with the amount you press the pedal to do the same amount of work..

[cassio]

i would say you will get better fuel economy by leting the engine rev a bit.. higher (lower numerically) gears will lug the engine a little more.. higher RPM might make you assume you will use more fuel but it really has to do with the amount you press the pedal to do the same amount of work..

wait what?

[sidriptide]

wait what?


higher RPM isnt a bad thing... lower RPM at the same speed would require more throttle.. the throttle position has a bigger effect on fuel economy..

i'm running 33s on 4.56s and a 5 spd and 70 mph on the highway is around 2800 rpm... i get 18 mpg on the highway now..

let it rev..

[Rawbrown]

I lost track of gas milage. but its pretty straight forward. I've run 31"s on 3.55's... crappy milage. it got better when I went to 4.10's. then I went 33"s and 4.88's. love the power but at 3k on the fwy did kill a tad more fuel. then came the 35's... I drive like crap around town and my jeep never really sees long hwy so mfg is gone to bfe... now that I have spend 3 minutes typing usless babble...babble...babble...
4.88's and 35"s is a greatsetup. and most are comfy with the MPG

[MudDawg]

The mileage improvement comes partially from running the engine near the torque peak in combination with higher manifold vacuum....the map sensor sees higher vac and the tps sees less throttle opening...a little leaner..more fuel economy...remember jeep doesn't use a mass air flow sensor...it relies on throttle position, rpm, map reading and IAT.

[Jump This]

higher RPM isnt a bad thing... lower RPM at the same speed would require more throttle.. the throttle position has a bigger effect on fuel economy..

i'm running 33s on 4.56s and a 5 spd and 70 mph on the highway is around 2800 rpm... i get 18 mpg on the highway now..

let it rev..

Sorry to hi-jack...but..... :D
Your rig runs comfortably at 2800rpm? It just seams to me like my XJ just isn't too happy with cruising at anything higher than 2400.....I'm running 4:88 with 33's until my 35's arrive and it just feels like running it up that high isn't right....:dunno:
Rick R

[cassio]

so 35's and 4.56 are a bad idea

or will they be ok!

i do alot of driving and need the good milage...

[Rawbrown]

Thats a combo that very few people are fond of...
so 35's and 4.56 are a bad idea

or will they be ok!

i do alot of driving and need the good milage...

[rocklandxjer]

i would listen to rawbrown, if you havent looked at his sig, he has s company that sells all drivetrain products including gears. he definately knows what hes talkin about

[Rawbrown]

what are you talkin about... I don't know squat.... I just won't SPOBI till I die...:viking::angel:
i would listen to rawbrown, if you havent looked at his sig, he has s company that sells all drivetrain products including gears. he definately knows what hes talkin about

[Jump This]

what are you talkin about... I don't know squat
Truth in advertising! Thats my kind of vendor!
Pick up those axels tomarrow Ryan?
:D
Rick R
BTW 4:88 and 35's
4:56 and 33's
4:10 and 31's
3:55 and anything stock...

[rocklandxjer]

ha lol