swapping 4.0 into a 2.5 comanche

i want to put a 4.0 into my 88 comanche 2.5l, has anyone done it? what does it entail? will i have to fab anything, like motor mounts, radiator brackets, will my 4spd tranny and transfer case fit? any help would be great guys! thanks

buy a complete jeep cherokee 4.0

swap EVERYTHING over from the cherokee to the comanche. it is all direct bolt-in, but the wiring is different.

so the interior has to come out on both vehicles, swap the

engine

transmission

shifters and linkages (depending on what you have i.e. manual/auto you will need to swap pedal assemblies)

motor mounts

radiators (remove the 2.5 rad support and bolt the 4.0 in)

transfercase

dash wiring and accessories including gauges

headlight wiring

engine bay wiring and accessories

you will need to cut the cherokee tail light harness out and splice the comanche one in, as well as swap the pump on the sending unit and splice the power for it into the 4.0 harness

but, with any year 1987 up, it is all direct swap. 1984 to 1986 cherokees, and 86 comanches require header panel work.

@#$% all that, thats more than i want to do right now, i really want to put a chevy 4.3 into it wich would be about the same time wise and work wise so ill just wait to put the 4.3 in. now i just gotta find a cheap 2.5 to get me through the winter. thanks for the info man, greatly appreciated!

I assure you, if you think swapping in a 4.0L is a lot of work, doing a Chevy 4.3 will be ten times more work. NOTHING will be bolt-in, and EVERYTHING will have to be custom adapted. A guy a few miles from me used to have an XJ with a 4.3 in it. I asked him once if he'd do it again. His answer was unprintable in a family-oriented forum, but the bottom line was "Hell [insert expletive of choice] NO!"

Remember, a 4.3 is just a small-block Chebbie with two less cylinder. For the work and fabrication involved, you might as well go with e 327/350. By contrast, everything you need for a 4.0L swap has already been designed and mass-produced. All you have to do is drop it in.

I assure you, if you think swapping in a 4.0L is a lot of work, doing a Chevy 4.3 will be ten times more work. NOTHING will be bolt-in, and EVERYTHING will have to be custom adapted. A guy a few miles from me used to have an XJ with a 4.3 in it. I asked him once if he'd do it again. His answer was unprintable in a family-oriented forum, but the bottom line was "Hell [insert expletive of choice] NO!"

 

Remember, a 4.3 is just a small-block Chebbie with two less cylinder. For the work and fabrication involved, you might as well go with e 327/350. By contrast, everything you need for a 4.0L swap has already been designed and mass-produced. All you have to do is drop it in.

if your gonna go 350 then you may as well go 372/383/400

See MJJeff's post in the build up area. He just finished this swap, and did a rather good job of it... 90% of his parts came from rigs I had stripped over the yrs, and were sitting in my garage.

MJeff87 just finished his a couple of weeks ago. Go to Projects and look at his thread "2.5 to 4.0 swap". Very well documented.

**Edit: oops, sorry PingPong, didn't see your post. Should have known you'd be on that being it was your 4.0 he used! :doh: :dunce:

Not a difficult swap, just a lot of work and a bit time consuming. Like Eagle said, all the 4.0 stuff is bolt-in, you just have to get the right parts. I used an ’89 MJ (automatic) underhood wiring harness and simply plugged it into the bulkhead connector for the stock interior harness (did A LOT of research and pinned out each circuit to make sure it would work). In addition to the harness, you’ll need:

-4.0 ECU (grab this when you get the underhood harness)

-4.0 frame horns (they bolt onto the framerails and the correct holes/studs are already there)

-4.0 motor mounts (2.5 ones are smaller)

-4.0 radiator and hoses (remove the 2.5 radiator brackets and the holes for the 4.0 rad are already there)

-coolant resivoir or some sort if you run an open cooling system (I reused my 2.5 one with some modifications)

-4.0 fuel pump (2.5 may be enough psi to start it, but won’t push enough volume)

-4.0 transmission (AX15), new flywheel, clutch, pilot bearing and transfer case (23 spline)

-new driveshafts, front and rear

You’ll also have to splice the 4.0 fuel supply and return lines to the 2.5 lines….for whatever reason the 2.5 lines have a connector where the rubber lines meet the hard lines on the framerail, but the 4.0 lines don’t. I just disconnected the 2.5 lines at the connector and slipped the rubber fuel lines over the hard lines and double clamped them. I also reused the 2.5 MAP sensor and ICM, they are the same parts for both engines, interestingly.

Jeff

Not a difficult swap, just a lot of work and a bit time consuming. Like Eagle said, all the 4.0 stuff is bolt-in, you just have to get the right parts. I used an ’89 MJ (automatic) underhood wiring harness and simply plugged it into the bulkhead connector for the stock interior harness (did A LOT of research and pinned out each circuit to make sure it would work). In addition to the harness, you’ll need:

 

-4.0 ECU (grab this when you get the underhood harness)

-4.0 frame horns (they bolt onto the framerails and the correct holes/studs are already there)

-4.0 motor mounts (2.5 ones are smaller)

-4.0 radiator and hoses (remove the 2.5 radiator brackets and the holes for the 4.0 rad are already there)

-coolant resivoir or some sort if you run an open cooling system (I reused my 2.5 one with some modifications)

-4.0 fuel pump (2.5 may be enough psi to start it, but won’t push enough volume)

-4.0 transmission (AX15), new flywheel, clutch, pilot bearing and transfer case (23 spline)

-new driveshafts, front and rear

 

You’ll also have to splice the 4.0 fuel supply and return lines to the 2.5 lines….for whatever reason the 2.5 lines have a connector where the rubber lines meet the hard lines on the framerail, but the 4.0 lines don’t. I just disconnected the 2.5 lines at the connector and slipped the rubber fuel lines over the hard lines and double clamped them. I also reused the 2.5 MAP sensor and ICM, they are the same parts for both engines, interestingly.

 

Jeff

thanks for the info man! i got a 2.5 for $50 that I'm just gonna run for the winter. when i get more time and money i plan on doing 4.0 swap, and I'm sure ill be pm'ing you with questions when i do. lol. again thanks for all the info

my 4.0L in my 2.5L was so simple...

took about 10 min and two straps.. no fab work..

didnt budge the whole trip.. :clapping:

my 4.0L in my 2.5L was so simple...

took about 10 min and two straps.. no fab work..

didnt budge the whole trip.. :clapping:

WTF???? :huh???:

he means he threw it in his bed :P

my 4.0L in my 2.5L was so simple...

took about 10 min and two straps.. no fab work..

didnt budge the whole trip.. :clapping:

That's step 1, the easy part:

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It's steps 2 thru 116,498 that are the biotch ;)

Jeff

oh, lmao. i was confused there for a sec :wall:

hey I'm about 15 miles from you and i can't seem to find any comanche around here worth buying for under 500. whered you get one for $50? interested in selling any MJ's?

hey I'm about 15 miles from you and i can't seem to find any comanche around here worth buying for under 500. whered you get one for $50? interested in selling any MJ's?

your from duraham? no kidding thats right down the rd. i paid 800$ for the jeep itself then 700$ for the tires. lol

I assure you, if you think swapping in a 4.0L is a lot of work, doing a Chevy 4.3 will be ten times more work. NOTHING will be bolt-in, and EVERYTHING will have to be custom adapted. A guy a few miles from me used to have an XJ with a 4.3 in it. I asked him once if he'd do it again. His answer was unprintable in a family-oriented forum, but the bottom line was "Hell [insert expletive of choice] NO!"

 

Remember, a 4.3 is just a small-block Chebbie with two less cylinder. For the work and fabrication involved, you might as well go with e 327/350. By contrast, everything you need for a 4.0L swap has already been designed and mass-produced. All you have to do is drop it in.

if your gonna go 350 then you may as well go 372/383/400

Then there is the final one: 454

I just happen to have one for sale with TH400 for $1200. Comes in a nice, portable package that looks like an '81 Chev C20 with 14 bolt rear and 4.10 ratio (5th wheel hauler with less than 80,000 miles on it)

On 10/27/2008 at 11:28 AM, mjeff87 said:

Not a difficult swap, just a lot of work and a bit time consuming. Like Eagle said, all the 4.0 stuff is bolt-in, you just have to get the right parts. I used an ’89 MJ (automatic) underhood wiring harness and simply plugged it into the bulkhead connector for the stock interior harness (did A LOT of research and pinned out each circuit to make sure it would work). In addition to the harness, you’ll need:

 

-4.0 ECU (grab this when you get the underhood harness)

-4.0 frame horns (they bolt onto the framerails and the correct holes/studs are already there)

-4.0 motor mounts (2.5 ones are smaller)

-4.0 radiator and hoses (remove the 2.5 radiator brackets and the holes for the 4.0 rad are already there)

-coolant resivoir or some sort if you run an open cooling system (I reused my 2.5 one with some modifications)

-4.0 fuel pump (2.5 may be enough psi to start it, but won’t push enough volume)

-4.0 transmission (AX15), new flywheel, clutch, pilot bearing and transfer case (23 spline)

-new driveshafts, front and rear

 

You’ll also have to splice the 4.0 fuel supply and return lines to the 2.5 lines….for whatever reason the 2.5 lines have a connector where the rubber lines meet the hard lines on the framerail, but the 4.0 lines don’t. I just disconnected the 2.5 lines at the connector and slipped the rubber fuel lines over the hard lines and double clamped them. I also reused the 2.5 MAP sensor and ICM, they are the same parts for both engines, interestingly.

 

Jeff

When you say you used the stock interior harness and connector did the 4.0 connector plug into the 2.5 without modifications? or you had to repin the connector? Couldn't you have just used the xj fuseblock?

Plugged right in at the C100 connector (the engine side of the fuseblock).  I didn't touch the interior harness at all.