Yellow01xj
NAXJA Forum User
- Location
- Arvada, Colorado
Would changing out the stock gears on my 2001 XJ to 4.56 or 4.88's give me better gas milage? I am running 31" tires. :dunno:
Gear Swap = Better Gas Milage?
- Thread starter Yellow01xj
- Start date
Stang5lgt
NAXJA Forum User
- Location
- Parker, CO
With 31s I would stick with 4.10s. 4.56s would make your engine scream on the on the Highway and kill your mileage. If you have 5 speed 3.73s would be a good choice.
Yellow01xj
NAXJA Forum User
- Location
- Arvada, Colorado
It's the automatic. Thanks!
Stang5lgt
NAXJA Forum User
- Location
- Parker, CO
http://4lo.com/calc/geartable.htm
It will be alright for OFF road but you will get tired of rowing so much in town.
It will be alright for OFF road but you will get tired of rowing so much in town.
Stang5lgt
NAXJA Forum User
- Location
- Parker, CO
I am going to be running 4.10s with 35s cause my XJ sees alot of road use.
DutchVDub
NAXJA Forum User
- Location
- Milliken, CO
Actually using the cross multiplication method in the tech section a manual transmission equipped 4.0 needs 3.60 gears to perfectly match w/ a 32" tire. That means 3.56's from an auto equipped XJ's axles would be a really close match.
BTW, correcting your gearing back to near stock makes your speedo and odo more accurate.
BTW, correcting your gearing back to near stock makes your speedo and odo more accurate.
Stang5lgt
NAXJA Forum User
- Location
- Parker, CO
True but gearing it down gives ya better seat of pants feel.
- Location
- Colorado Springs, CO
3.55's and 30's, good.
3.55's and 31's, not so good.
4.11's and 31's, I'm in 5th gear at 40 if it's flat. In my experience with a manual tranny 32's and 4.11's would be a good all around gearing. When you lift and put on bigger tires, you add considerable drag due to air resistance and road friction. That's been my experience. Then again, I know more than one person who has 31" tires and a four inch lift who wishes they had 4.56's rather than 4.11's.
I'm not so concerned about crawl ratio since I have a 4-1 transfercase.
Fred
3.55's and 31's, not so good.
4.11's and 31's, I'm in 5th gear at 40 if it's flat. In my experience with a manual tranny 32's and 4.11's would be a good all around gearing. When you lift and put on bigger tires, you add considerable drag due to air resistance and road friction. That's been my experience. Then again, I know more than one person who has 31" tires and a four inch lift who wishes they had 4.56's rather than 4.11's.
I'm not so concerned about crawl ratio since I have a 4-1 transfercase.
Fred
philip_g
NAXJA Forum User
- Location
- back in CO
I run 31's on my manual and 3.56's are perfectDutchVDub said:
DutchVDub
NAXJA Forum User
- Location
- Milliken, CO
philip_g said:
I'll be running those w/ my 32's. When it comes time for my 35's I'll be swapping to some 4banger axles. Again using the cross multiplication I would need a 3.90 something to match stock w/ 35's, so 4.10's will be perfect. I'll get more low gear w/ a simple transfercase rebuild/regear. You only need the super low gears for wheeling and thats what 4lo is for, 4hi is for snow covered streets.
swbooking
NAXJA Forum User
- Location
- Riverside/Running Springs, Ca
I DD my XJ and drive about 200 miles a week, 4.10s and 35's with an AX-15 suck... Its OK for flat / around town, but the minute you head up a mountain or hill, say hello to all the truckers that pass you... I'll be going to 4.56 or 4.88s on the next set of axles.
To the OP, i wouldnt go above 4.10s. You'll be reving very high on the freeway and it will ruin your milage.
To the OP, i wouldnt go above 4.10s. You'll be reving very high on the freeway and it will ruin your milage.
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DutchVDub
NAXJA Forum User
- Location
- Milliken, CO
Thats what a supercharger is for. 
Stang5lgt
NAXJA Forum User
- Location
- Parker, CO
Why don't you down shift. I have 35s and 3.55s and have no prob running up the mountain at 70 mph.swbooking said:
swbooking
NAXJA Forum User
- Location
- Riverside/Running Springs, Ca
Cause gas is $4.00 a gallon and id like to get better then 10mpg... Yeah i used to have 33's and 3.07s and run like a bat out of hell. Plus i have a 210K RENIX, i try to be nice to it.
philip_g
NAXJA Forum User
- Location
- back in CO
Stang5lgt said:
jesus. I bet that sucks gas like no other.
Stang5lgt
NAXJA Forum User
- Location
- Parker, CO
17mpg last tank. I love 5 speeds.philip_g said:
Stang5lgt
NAXJA Forum User
- Location
- Parker, CO
My speedo is about 15% off. So when I figured the mileage I figured with about 10%. So I wouldn't be giving the XJ more. Trick is to keep the engine in 2k rpm range. I never use over drive. Plus I have HO engine with Renix injection. Better flowing heads and running the stock HO exhaust manifold. Jeep has been pretty good to me just hit 220k this week.
DutchVDub
NAXJA Forum User
- Location
- Milliken, CO
If you run a higher RPM w/ less throttle to get up the hill you are actually burning less mileage and hurting your engine less than keeping it bogged down in a lower rpm with a lot of throttle. Low rpm and high engine load mean less oil pressure and more bearing stress. I've seen plenty of evidince for this when I rebuilt engines for the Army. Part of the reason the Army went to automatic transmissions in everything is because people don't know how to drive a manual properly.
