Completely NUTS - 4x4 -> 4x2 convertion

I know you all must think I'm nuts, but... I already have 2 4wd cherokees and I need something with good gas mileage to drive around town. I drive a LOT for work, 100 miles every day at least. I can't get a car because I have to haul a bunch of newspapers. So I was thinking about converting my MJ 4x4 to 2wd. The reason for this is because I recently learned that buying a 4 banger won't save me gas. (see toyota thread) Turns out that MPG are dependent upon horsepower to weight ratio and final drive gearing.

Since my MJ is unibody I've got a good head start in the weight department. I can drop more weight by losing all 4wd components. Then I plan to stick some small tires on it to improve the gearing for good gas mileage. I'm not concerned as much about the drag of the front axle and t-case as I am about their wieght. I figure a lighter truck requires less throttle, hence uses less gas.

I had made up my mind to buy a yota truck, and I went to do some research on their forum. Turns out, everyone on there who went from a big engine vehicle to a toyota was disappointed! Here's the thread:

http://www.4x4wire.com/forums/showflat.php?Cat=&Number=459270&page=&view=&sb=5&o=&fpart=all&vc=1

These guys claim their 4 bangers are getting 18-20MPG, and that's about what my XJ and MJ gets. Seems to me there is no reason to get a 4 banger, as one of the posters in that thread explains. I could think of no one else more likely to hype up their MPG claims than the owners of the trucks in question, but these guys are actually claiming disappointment with their gas mileage!

This is when I decided to keep the MJ and lighten it up. To me its not a lotta work, and I've done it before with 4x4 axles, so this should be a breeze to do.

Am I nuts or am I onto something here?

SimpleXJ

If its your DD and you already have 2 4wds and you don't need it on this one, why not? The 2wd XJs get like 23 mpg on the hwy, with as expensive as gas is I'd do it.

if can find a diesel, grab it...you'll see near 30 or better on the highway

to bad your so far away, I'm doing just the opposite, I have the 2wd AW4 and front i beam.

(1) The 4-bangers do deliver better gas mileage than the 6-cylinder models, gearing aside. But you have to be willing to accept that fact that no matter how hard you flog it, it can't go as fast or accelerate as quickly as a 6-cylinder.

(2) If you want economy, you may be wasting your time converting an MJ. The MJs weigh just about as much as the XJs.

also too small a tire will make you spin higher rpms at speed killing the mpg.

find yourself a cheap jap car. i bought a 91 sentra for 600 bucks in august. since then ive put 20k miles on it, gotten 30-35 mpg consistenly (depending on if i had my bike and or canoe on the roof blocking wind, and how much weight i was carrying inside), driven it up and down the east coast, and had it on snow covered forest fire roads where 2wd p/u's couldnt go.

Hunter

If you need mpg and storage space, get a station wagon. Don't destroy a 4x4...sell it and let someone use it.

Atl XJ said:

If its your DD and you already have 2 4wds and you don't need it on this one, why not? The 2wd XJs get like 23 mpg on the hwy, with as expensive as gas is I'd do it.

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I have a tuned up, bolt-ons, weight reduced 94' RWD, and I get 14-16 mpg on the highway. 9-12mpg around town.

Eagle said:

(1)
(2) If you want economy, you may be wasting your time converting an MJ. The MJs weigh just about as much as the XJs.

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Actually, technically, MJ's weigh about 100 lbs more than a similarilty equipped XJ. I didn't beleive it either. Source: Autotrader.com curb weights.

JnJ: Since you've got the 2wd AW4 out, does it look like the tail end of the tranny can be swapped or is the output shaft different between 2wd and 4wd models?

Eagle:
4 bangers do get better mileage but not by much. Take a look at the toyota thread I linked to, and if you want, check out www.fueleconomy.gov - they have a database of gas mileage estimates on everything 1985 and newer. Look at a 93 nissan and yota 2wd auto pickups, they get:

Nissan: 21/26
Yota: 22/25

my XJ currently gets 18/21, so I would be gaining 4-5 MPG tops, and I'll owe 5 grand on a new truck. Or I can dump a week and about $100 into lightening up my MJ and not owe anything. If you compare the 4x4 yota and nissan, they get worse mileage than the 4x4 XJ.

About the weight of the MJ/XJ - MJ's curb weight is about 3000lbs, 4wd model. Both yota and nissan 4x4 trucks weigh 3300 curb weight. If you compare 2wd models, MJ 2wd weighs 2800lbs, nissan 2wd - 2800lbs, yota 2wd - 2700lbs. I don't know how reliable these figures are, but its all I could get.

Do you guys still think this is a waste of time idea? If so, what advice would you give me? Remember, I can't get a car because I haul stuff.

Thanks,

SimpleXJ

SimpleXJ said:

JnJ: Since you've got the 2wd AW4 out, does it look like the tail end of the tranny can be swapped or is the output shaft different between 2wd and 4wd models?

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I believe you do have to replace the output shaft, but I'll take a closer look tonight.

Since your MJ is already a disconnect front axle you are not gaining measureable reduced friction by replacing the 4wd with 2 wd axle. The only difference is about 180 lbs in weight of the 4wd truck over the 2 wd shipping weight.
I would suggest putting 215 tires on the standard 6" wheels, installing a K&N flat filter in the airbox, and replacing the stock CPS with the hi-altitude one. With that setup you can get 20+ MPG with decent plugs,wires cap and rotor. Driving habits make more difference im MPG than swapping 4WD for 2.
However if you really have to have a 2WD; I have a 120K 89 4.0 and 5 sped trans that you can pick up in RI for $300.

When your trying to shed weight, 180lbs is a good size chunk.

buy a car

If you're serious about doing the conversion, I've got a stock MJ 2WD beam axle that you can have for dirt cheap (read free if you come get it). It's a leftover from my 2->4WD conversion. It'll probably save you some rolling weight (???) Let me know if you're interested...it's just sitting in a corner of the garage gathering dust right now.
Jeff

Five speed, 3.07, and 235 tires make a huge difference; I average between 22 and 26 mpg with a 150K old 4.0 Cherokee. This is comparable, and perhaps somewhat better, than what I obtain with a Toy 4-banger having 4.10s and 31 inch tires.

JeffinVA- where are you located?

SimpleXJ

Re: Jeff 2 wd axle

Jeff please contact me at [email protected] about your 2WD axle.

get a geo.