Re-gearing the AX15, effect on MPG?

[ZachsXJ]

If I were you I'd stick with the stock 3.07s. I've got an AX15 with 3.55 geared D30/8.25 swapped in, 31x10.50s and the gears are still a little shorter than I'd like.

If you're getting 20 something mpg, don't mess with anything because you're getting about the best gas milage of anyone in an XJ. 3.55s will hurt your gas milage because of the extra umph needed to keep the 4.0 spinning at 2200-2700rpm. I know on the highway cruising in 4th gear at about 2700 my XJ drinks gas like a boss.

 

[Breezio69]

No off road, it's strictly a daily driver. That's why this is in the "Street and Performance" forum. I've managed to steer through a couple of pretty scary situations in bad weather, partly thanks to the ABS.

Understandable, my experience with ABS has been less than stellar, so I personally have a vendetta against it. I have had ZERO accidents with either brake setup, but owning 3 vehicles with ABS (minus 1 now since the ABS delete on the XJ) I've slid into more intersections/ almost cars in the snow than I ever have in an ABS vehicle vs non... and im not an overly aggressive driver... I could stop a full size non ABS Bronco before my ABS XJ/Passat/A4 in the snow, till I got rid of the junk.

Just sayin, and just my opinion

 

[plinkerneil]

Breezio69 sez:
my experience with ABS has been less than stellar, so I personally have a vendetta against it

That's true, ABS isn't the greatest thing when you just need to snowplow. I don't deal with a lot of deep snow anymore, my bad weather is mostly oil spots caused by spring rains or spotty ice. Stuff that causes loss of traction in one or two tires and then they catch again. Just the kind of thing that ABS and limited-slip were designed for.

ZachXJ sez:
If you're getting 20 something mpg, don't mess with anything because you're getting about the best gas milage of anyone in an XJ.

That's a very good point, and that's why I started this thread. I'm hesitant to mess with the magic. I will say that before I put the CAI on, I wouldn't have even thought about this--the engine would start gasping for breath above 2200 or so. I wish I could try driving around in 4th for a while, but like I said I've got a bent D30.

 

[Breezio69]

and 20 mpg the way it sits... i would just find a new D30 w 3.07 to replace your bent one, i get barely over half of what you get at about 11.5 mpg with 50/50 highway/street driving with 33x10.50's

 

[DanMan2k06]

For the love of God let's not even start up the ABS opinions here. It can be done, it's not easy, and requires some machine shop work = generally not cheap. If you don't plan on running bigger tires stick with the Dana 35 and your current ABS.

At our local pick and pull, axles run $60, including shafts, without brake rotors or drums. That $120 won't even buy you a set of gears...

 

[plinkerneil]

At our local pick and pull, axles run $60, including shafts, without brake rotors or drums. That $120 won't even buy you a set of gears...

That's true enough. But that still leaves the question of whether anybody has re-geared the AX-15 on stock-sized tires? Other than gradon and his stroker, I mean. And there's Dan's friend, but I didn't hear anything about gas mileage after the swap. I'd like to know how it worked out for somebody before I decide on this.

 

[seanyb505]

I did it before the stroker. I had a slight decrease, but that could be attributed to the my driving style (it was quicker). At 70mph and your size tires, your engine will be spinning 315rpm faster with 3.55's compared to stock. I felt that the engine was able to spin a little more freely after regearing, so if I wasn't in a hurry or driving for fun it didn't need as much throttle to get to speed. Do it.

 

[87manche]

I posted my thoughts in your other thread.

but

3.55's and 31's with an AX-15 is basically stock gearing. I used to get 23-25 MPG in my MJ on stock suspension with 31's. Your speedo will even be right.

3.73's and 31's dropped maybe another MPG. speedo offf a few MPH @60.

3.73's and 34's dropped me to about 18, but they were bias ply super swampers.....

I've not driven it on the highay with 4.56's and 35's.

 

[Johnnie Walker]

I believe that if you find a Turdy5 w/out abs, that you can swap axle shafts with your current ones that have the tone rings on them.
Not sure, but the Liberty's had C8.25's if any of them had ABS, would be easy to convert a non-Liberty C8.25 to ABS.

 

[plinkerneil]

Not sure, but the Liberty's had C8.25's if any of them had ABS, would be easy to convert a non-Liberty C8.25 to ABS.

That's an interesting idea. Do you think the Liberty tone rings would have the same number of teeth as the XJ?

EDIT: Oops, that's a no-go. Read this. The Liberty ABS system uses three sensors, one at each front wheel and a single one on the ring gear in the rear diff. The XJ requires one on each wheel.

http://www.jeepforum.com/forum/f11/kj-liberty-rear-axle-8-25-parts-into-xj-8-25-a-683719/

 

[kastein]

was going to say. The 8.25 never had factory 2-sensor ABS, the funny looking cast bumps and flat spot in the center top of the housing is where the ABS sensor mounts if it's been machined on that axle.

Somewhere around here there is a thread on putting ABS on a d44 and another one on putting it on an 8.25 though.

 

[MoparManiac]

I thought this thread was about changing the gears inside the AX-15.

I was really curious/interested.

:laugh:

 

[ktm racer 419]

I thought this thread was about changing the gears inside the AX-15.

I was really curious/interested.

:laugh:

x2 lol

 

[DanMan2k06]

I thought this thread was about changing the gears inside the AX-15.

I was really curious/interested.

I may be completely off my rockers here, but haven't people changed out the overdrive gears for better mileage? Or is this part of the entire cluster? I vaguely remember hearing/seeing/reading this somewhere. Go easy it's been a rough week :/