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Unread 10-12-2001, 06:58 PM   #1
Keith
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2.5L to 4.0L

What all is involved from going to the 2.5L to the 4.0L. I've read the frames are different?

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Unread 10-12-2001, 07:11 PM   #2
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yes the frames are diferrent.the t-case input in 2.5 is 21 spline.it's 23 spline on the 4.0.there's a slight difference in driveshaft lengths as well.you know the other obvious diffrences.it's not impossible,might be cheaper to just by a 6 cyl jeep.don't know for sure.
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Unread 10-12-2001, 07:14 PM   #3
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What frame modifications would have to be made to fit the 4.0?
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Unread 10-13-2001, 12:39 PM   #4
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i can't remember for sure,i think you have to move the mounting point on the frame forward.the 4 banger,as you know,is stuffed in all the way at the fire wall.
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Unread 10-14-2001, 09:38 AM   #5
osburn
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Yeah, the motor mounts are different, as far as the frame goes. Cut them off and weld on new ones is all.
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Unread 10-14-2001, 11:32 AM   #6
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for all thats involved in swapping in a 4.0 it would cost the same to do a v8 swap or if you want a 6 get a gm4.3 v6 these can be done easily and they swap into the 4cyl wranglers easier then a 4.0....have you driven a 4.0 i ask because that motor is a dog in my oppinion but i have a preference for v8's as i have had them all my life...i have a 89 yj also and am going the 302 swap with a c4 auto and a dana 20 out of an early bronco.
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Unread 10-16-2001, 07:07 PM   #7
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Quote:
Originally posted by fuelin:
for all thats involved in swapping in a 4.0 it would cost the same to do a v8 swap or if you want a 6 get a gm4.3 v6 these can be done easily and they swap into the 4cyl wranglers easier then a 4.0....have you driven a 4.0 i ask because that motor is a dog in my oppinion but i have a preference for v8's as i have had them all my life...i have a 89 yj also and am going the 302 swap with a c4 auto and a dana 20 out of an early bronco.
I agree that with all the work, you could install a small block in there. Probably cost less since those engines are plentiful. Lots of trans options available too. I'd probably go with a 4.3L Vortec for a 6. Maybe a 5.2L Magnum or a 5.7L Vortec or maybe a new Vortec 5.3L. Unless you're limited by what engine you can install (Some states will only allow a engine that was offered) then I'd see what else you can do with it.

The frame is not different. The frame mounts for the engine are. But you can do away with it with a AA engine mount. The input shaft on the Tcase will also need to be swapped. Depending on the year there will be differences in fittings for the PS box and pump, unless you swap back to the 2.5L's.
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Unread 02-28-2002, 05:22 PM   #8
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how well would a 2001 4.0l fit into a 2.5L 91 yj. if i was able to get motor ,tranny ,transfercase, and driveshafts?
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Unread 02-28-2002, 05:29 PM   #9
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i would go with a v8 but i can get these for free so i want to take advantage of it.
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17 year old with a 1991 four banger
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personal quote:"it didnt look that deep dad, i swear!"(first time stuck in mud)
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Unread 02-28-2002, 05:30 PM   #10
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also any writeups or web pages would be nice!
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17 year old with a 1991 four banger
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-32's on the way
-KC's on the windshild
personal quote:"it didnt look that deep dad, i swear!"(first time stuck in mud)
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Unread 03-01-2002, 06:52 AM   #11
Don Tibbetts
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If you can get all of that stuff for free I would say you just lowered you costs considerably. I read somewhere that Jeep offers a conversion kit. I don't know what all is included. If you can get all that stuff for free, I would think that it would be worthwile. I'd give it a shot. It sounds like your biggest problem would be changing the engine mounts and mounting location. This is a small amount of effort to transform you Jeep and even update to newer technology.
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Unread 03-03-2002, 11:03 AM   #12
jerrys yj
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where can i find this conversion kit at?
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Unread 03-03-2002, 01:23 PM   #13
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Free doesn't mean better. All the work you'll have to put into it for such little performance really isn't worth it. You can get a Chev 350 or Ford 302 (mustang 5.0, well..4.6 motor) for about $100 in a junkyard, and spend maybe $1,000 building it up and you'd have quite a powerful motor. Trans, if you're going balls to the wall, is going to be $1,000 max, and transfer case really varies. But the fun you'd have would more than make up for it.

I'm in the process of doing a Chev 350 conversion myself, and I'm using this site as a guideline. Very helpful..you should seriously consider going V8.

This is the website for Advance Adapters. The adapters for a 350 are child's play.
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Unread 03-05-2002, 06:34 AM   #14
Don Tibbetts
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Check this page out for info about a 302 V8 swap.
http://www.bc4x4.com/chrisw/default.asp
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