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Old 08-25-2013, 11:10 PM   #1
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2.5 vs 4.0

I'm thinking of swapping my 2.5l engine out of my 91 wrangler for a 4.0l from a 91 wrangler whats the difference in the dtive train? Or would it be better to bore the cylinders on my 2.5l

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Old 08-26-2013, 12:06 AM   #2
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Swapping the engine to anything other than a stock 2.5L entails replacing most of the driveline. Transmission won't handle any more power, t-case can be used but will need to be converted to use with the new transmission. Most of the wiring harness can be used, you will have to swap computers and wire in additional injectors.

Axles will be geared very short with 4.10 gears which will make the engine run high in the RPM's on the highway, so you need either 32-33" tires, which will mean you need a stronger rear end, not only to handle the additional torque, but the bigger tire size. The stock Dana 35 rear is a toothpick.

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Old 08-26-2013, 07:44 AM   #3
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Dunno if it is worth it to go from 2.5 to 4.0 honestly, have you considered swapping in a v8?
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Old 08-26-2013, 09:03 AM   #4
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Yeah. But I know that I would drastically have to change the entire drive train
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Old 08-26-2013, 10:30 AM   #5
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Originally Posted by gagedunlap16 View Post
Yeah. But I know that I would drastically have to change the entire drive train
I'm not 100% but I think you'd have to change everything anyway (ax-5 to an ax-15, motor mounts, etc)
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Old 08-26-2013, 10:32 AM   #6
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I'm not 100% but I think you'd have to change everything anyway (ax-5 to an ax-15, motor mounts, etc)
You are correct, ECU, Tranny, Mounts, ETC all would need to be swapped if converting to a 4.0. IMO the 8 makes more sense. I know when my 2.5 inevitably goes, im throwing a small block in.
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Old 08-26-2013, 11:55 AM   #7
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V8 definitely makes more sense. I have a 96 Grand Cherokee with a 5.2L that's being transplanted into the YJ. Picked the whole thing up for cheap in running shape, plus it has everything inside of it that I would need to get the engine running.

Donor cars are the best route to go.
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Old 08-26-2013, 04:45 PM   #8
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V8 definitely makes more sense. I have a 96 Grand Cherokee with a 5.2L that's being transplanted into the YJ. Picked the whole thing up for cheap in running shape, plus it has everything inside of it that I would need to get the engine running.

Donor cars are the best route to go.
I wonder if my wife would notice if I swaped her 5.9 Durango motor for my 2.5 ?
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Old 08-27-2013, 06:00 AM   #9
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I wonder if my wife would notice if I swaped her 5.9 Durango motor for my 2.5 ?
shell never know.

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