Keep 2.5 or trade up to 4.0

M

M G D

New member
Year ago I bought a 93' YJ 2.5 manual w/130K on 32x11.5x15's 4" lift w/ stock gearing, learned alot about Jeep's since then & like everything about em.
Took couple of camping trips this summer & I go through a lot of oil but no smoke screen out the back or puddles under the jeep, it just disappers @ the rate of (get this) a qt every 100 miles. Not kidding, little excessive eh?, a qt of Mobile extendeded life formula synthetic disappers every 100 mi's. My son trailing behind see's a bit of exhaust smoke & some puffs when it sits then starts off but again no embarrassing smoke screens, the compression test is 145,158,160,175. I was going to rebuild the 2.5 but am wondering if trading in a 4.0 is worth the effort, I've read a bunch of articles and threads & find it's about 50/50 pro and con. I like the 2.5 just fine for crawling but need to highway drive to the ORV park at about 60+, money is an issue, I can't trade to a 4.0 rig & if I keep the 2.5 I'm adding an efan, TBS, cold air inlet and exhaust upgrade. Any opinons are greatfully accepted. Thank you. MGD
 

well when i had my XJ's one had the 2.5 and the other had the 4.0 and i would go with the 4.0 any day of the week. im thinking about putting a 4.0 in my 73 cj5 and get rid of the 304 but thats just me haha and to me the 4.0 has a lot more power then the 2.5 and i had nothing but problems with the 2.5. i was always putting money into it unlike the 4.0 and i beat the 4.0 up and still running
 
My vote is to rebuild the 2.5 or sell it and buy a jeep with a 4.0. To put a diferent engine in any vehicle is a lot of work. Almost everything is diferent.
 
steady.foot said:
My vote is to rebuild the 2.5 or sell it and buy a jeep with a 4.0. To put a diferent engine in any vehicle is a lot of work. Almost everything is diferent.
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^^^
this, once you swap motor mounts, you will still need to swap wiring harness or pin out the exhisting one and mating it to a new one, you will have to replace the transmission; the AX5 is not up to the extra torque of the 4.0, so you will have to look for a AX 15 or go auto with a AW4. plus other small nickle dime stuff.

It is definately doable, but if it were me and I was going to invest this much time and money and energy into a swap, I would look for a votect 5.7 or 5.3 and swap one of those in. It might cost a bit more, but well worth it.
 

jps4jeep said:
^^^
this, once you swap motor mounts, you will still need to swap wiring harness or pin out the exhisting one and mating it to a new one, you will have to replace the transmission; the AX5 is not up to the extra torque of the 4.0, so you will have to look for a AX 15 or go auto with a AW4. plus other small nickle dime stuff.

It is definately doable, but if it were me and I was going to invest this much time and money and energy into a swap, I would look for a votect 5.7 or 5.3 and swap one of those in. It might cost a bit more, but well worth it.
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I agree with the previous 2 posts; if you are gonna do an engine swap, don't go for the 4.0L but rather go in the V8 direction and make it really worth your while. If it were me, I would rebuild the 2.5L and consider increasing compression to 10.5 (you say $$ is not a problem; you would have to run premium fuel, but other than that no other changes are really necessary), which will make it quite a bit more powerful. Then maybe regear to 4.88 if you want some extra ooomph.
 
I purchased my 92 YJ a little over 3 years ago with the 2.5L in it. It had a little
over 143,000 miles on her when I bought her. I made the most out of her by
doing all the little power boosting mods with very good success. She now has
over 167,000 miles on her. I went back and forth with the decision on weather
to rebuild the 2.5L motor, upgrade to a 4.0L motor or go with a V8. Cost wise I
decided to look for a project 4.0L donor vehicle. I found a complete running 99
Cherokee XJ with 96,000 miles on it. It came with the 4.0L motor - AX-15/5-
speed manual and the N231J T-case combo. It was an insurance write off from
an auto accident that the insurance company totaled. It came with a salvage
title. Starts and runs great. This way you also get the ECU, wire harness, Alt
Starter, Water Pump, Radiator and all brackets needed to do the swap. Total
Cost was $800.00 This is a great, cost effective option for an upgrade.
 
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I agree with jonzjeepyj i have a 95 yj that i did the 4.0 swap on and the best way isto get a donnor vehical mine was a 95 xj that had wicked frame rot i got for 400 bucks.i ended up reusung the 4cly wire harnes, radiator and tranfercase shifter assemmbly. u will have to fabricate new motor mount perches and drill new holes for your trann mount.
 

Also if you don't want to through so much oil, get rid of the synthetic oil. Synthetic oil is a lot thinner than conventional oil, therefore Burns quicker and leaks out quicker.
 
Synthetic oil doesn't smoke much in an engine that burns oil. I have a cousin who works at a rather shady used car lot and he told me they put Mobil 1 in cars that burn oil because people won't see smoke (although the cars still burn oil).

A quart every 100 miles is excessive but your problem might be as simple as needing new valve seals. Get a compression check.
 
he did, compression is low on one and high on one with two being close


145,158,160,175

the two farthest exceed 15 percent
 

Valve seals on a 4-banger shouldn't cost that much. It's worth a shot. Rebuilt 4-bangers start at $1600. Cheaper than a new used Jeep. My .02.
 
4.0... price of gas is ridiculous these days, and your not going drag racing to require a 5.0 or 5.7, so why waste fuel and weight.. that 4.0 will do anything you need it to do other than out run that vette.. and swapping out a motor is a piece of cake.. everyone should do it at least once, teaches you whats under your hood and when something goes wrong, you know what you have!..
 
frhrwa said:
4.0... price of gas is ridiculous these days, and your not going drag racing to require a 5.0 or 5.7, so why waste fuel and weight.. that 4.0 will do anything you need it to do other than out run that vette.. and swapping out a motor is a piece of cake.. everyone should do it at least once, teaches you whats under your hood and when something goes wrong, you know what you have!..
Click to expand...

we all know what tim the tool man taylor would say

image-4046000104.jpg

MORE POWER!
 

If your worried about gas prices go with a V8 I can't imagine it would get less gas mileage than your 4 banger I say this because my 4 banger averages around 13mpg why not have something that will get the same gas mileage of not better but will actually be able to keep up with traffic
 
I can't figure out what you guys do to your 2.5L's.. mine got over 20mpg easily, everday, everywhere.. not much power like the biggies, but I did get better mileage than most of the cars out there on the road..
 

bugleboy said:
my dad has a 5.7L hemi in his charger and it gets 27mpg my 4.0L inline6 gets 13mpg :/
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When was your last tuneup? I'm knocking down a hair over 18mpg, that's with a 3" lift and 31" tires on my 4.0 gr. Cherokee. I also live where there are a good bit of hill's...
 
eric m said:
When was your last tuneup? I'm knocking down a hair over 18mpg, that's with a 3" lift and 31" tires on my 4.0 gr. Cherokee. I also live where there are a good bit of hill's...
Click to expand...

its been a while :/ im overdue
 
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