I have a 78' CJ-7 with a 401/T-18/dana 300/dana 44's with 4.09's/33" tires. I'm wanting to go with 35" tires when I get another set. The dilemma is that now with the 4.09 gear's, my jeep is really a gas hog. What I was wondering was if anyone has ever put something like a Toyota 20/22r 4cyl with the 5 speed transmission into a CJ? I know it seem's like it would be wrong from a jeeper point of view, but the 20/22r motor's are definately reliable and you would have to use some kind of 5 or 6 speed with it because I don't think the t-18 would be a good choice with a lower hp/torque engine like a 4cyl. What I'm getting at is what would be the best combo of 4 cyl engine/transmission for gas mileage and durability? I'm not looking to tow anything, just to go 4 wheeling on the weekend's and not have to spend a couple hundred buck's just on gas!
Swapping a 4cyl into a CJ-7
- Thread starter big_o_tom
- Start date
I think that any engine swap would be more expensive than buying a little beater car for daily driving.
It would be hard to overcome the aerodynamics of your CJ. I know that with TJs, the 4 cyl engine only gets 2 MPG more than the 6.
Fuel Economy 4 cyl Wrangler
Fuel Economy 6 cyl Wrangler
It would be hard to overcome the aerodynamics of your CJ. I know that with TJs, the 4 cyl engine only gets 2 MPG more than the 6.
Fuel Economy 4 cyl Wrangler
Fuel Economy 6 cyl Wrangler
TristateJeep
New member
You have the ideal set up for a JEEP right now. If you just changed the rear gear ration it would probably help the most. I would look at something in the 3:55-3:73 range. I am running 3:73 with my 35 in. tires and I don't think the mileage is too bad. Figure about 12 -16 MPG.
jarbidge09
New member
What about a 4.2 or 4.0 with fuel injection. I put the mopar injection on mine I get about 22-23 mpg or get one out of the jeep junkyard.
can't complainSaddle Tramp
New member
Been thinking of the gas issue too as we all have. When gas was cheap the only worry about mileage was how much extra gas did you have to carry to wheel away the day and still get back to the first filling station on the road home to buy more.
An I4 in a CJ is nothing new of course and I would think the Toyota R22 would do the job but my idea is going in another direction. Rather than smaller cubic inches under the hood leave the motor along and re-evaluate the gearing.
Currently I have 4.56 gears in the differentials. Couple that with the 32â€- 33†tires and no overdrive at 65 mph the motor is turning over 3,000 rpm. I have a 1978 AMC 401, a 1977 CJ T18, and a 1980 Scout Dana 300. The crawl ratio for that set up is 6.32 x 2.62 x 4.56 = 75.50. If I up the gearing in the pumpkins to 3.54 and install a TeraLow type kit in the transfer case fuel economy on the street should be improved while keeping a reasonable crawl ratio. For example: 6.32 x 4.0 x 3.54 = 89.49. The 401 should have plenty of power to push it all down the road in 4th gear while holding the rpms down.
An I4 in a CJ is nothing new of course and I would think the Toyota R22 would do the job but my idea is going in another direction. Rather than smaller cubic inches under the hood leave the motor along and re-evaluate the gearing.
Currently I have 4.56 gears in the differentials. Couple that with the 32â€- 33†tires and no overdrive at 65 mph the motor is turning over 3,000 rpm. I have a 1978 AMC 401, a 1977 CJ T18, and a 1980 Scout Dana 300. The crawl ratio for that set up is 6.32 x 2.62 x 4.56 = 75.50. If I up the gearing in the pumpkins to 3.54 and install a TeraLow type kit in the transfer case fuel economy on the street should be improved while keeping a reasonable crawl ratio. For example: 6.32 x 4.0 x 3.54 = 89.49. The 401 should have plenty of power to push it all down the road in 4th gear while holding the rpms down.
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I thought about that, changing the gear ratio again. The dana 44's had 3.07 gears in them until a few week's ago. That was really to high for the street. When the jeep belonged to my buddy it 4.10's, T-18, and a dana 20 x-case, low crawl ratio was about 53-1. With the 3.07's and a dana 300 the low crawl ratio was about 52-1. Now it's about 65-1. I'm just wondering, probably wont do anything but drive it and donate to the arab's.
