JK 4.0 HO Swap for real.

JKUndaunted

New member
Transfer case and auto shifter mounts built. I used a combination of the 545rfe/AW4 mounts and the 241/231 mounts to build each one.

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Bacon

Member
Hey guys. I'm new here and this is my first post so please bare with me. I killed my 545rfe in a lake at my local quarry. Took on 3 litres of sandstone lake water through the stupid vented dipstick tube. Managed to drive 23 miles home and once I turned off the jeep and started it again it wouldn't move. Transmission destroyed. I hated the crd motor anyway so sold it in perfect working order. So now comes the good stuff. Im swapping in the legendary 4.0 fully rebuilt with an AW4/241 combo. Do I have your attention?

Regards
Ollie

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You sir, have my attention. I love this idea. Did you consider a stroker?
 

JKUndaunted

New member
This 4.0 is from a 94 xj. I prefer the 91-95 xj's set up due to the simpler obd1 system.

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JKUndaunted

New member
You sir, have my attention. I love this idea. Did you consider a stroker?

I did consider the stroker but my ultimate goal was reliability and simplicity. My xj and JK will have identical engine/transmission aside from the transfer case. I also have a third engine and AW4 on standby if the need arises.

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StrizzyChris

New member
Well the CRD stinks. Only got 22 imperial mpg with 35's on 4.10 gears. My 91 2 door xj 4.0 HO/AW4 with 244,000 miles on it rollin on 33's with 3.55 gears gets 27 imperial mpg. Plus diesel is 10 pence (16 cents) per litre more in England.

Is this build done, and your now doing the write-up? Im sure you know that a 2d xj and a JKU is a completely different beast when it comes to weight and aerodynamics with its slightly laid back windshield. All the same, this is an interesting build and I am curious to see your subjective review on the power comparison and fuel economy. Always cool to see someone doing something different!
 

JKUndaunted

New member
Is this build done, and your now doing the write-up? Im sure you know that a 2d xj and a JKU is a completely different beast when it comes to weight and aerodynamics with its slightly laid back windshield. All the same, this is an interesting build and I am curious to see your subjective review on the power comparison and fuel economy. Always cool to see someone doing something different!

This is a build in progress. I know the 2 door xj is much lighter than the JKU. However I dont care about speed. I care about reliability and that sweet 4.0 sound. My JK is totally stripped out. No back seat, No carpet and the stock gas tank and skid has been removed and replaced by custom under floor rear mounted 16 u.s. gallon aluminium gas tank. and the 4.0/AW4 combo is considerably lighter than the crd/545rfe combo. The jeep sits about 1" higher than it did with the CRD.

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Jiffy05

New member
I'm really excited to see the final product of this build. It is very odd going backwards like this but the 4.0 is a very good motor.
 

JKUndaunted

New member
I'm really excited to see the final product of this build. It is very odd going backwards like this but the 4.0 is a very good motor.

I dont consider this going backwards. I hate modern technology and the minimalist rubbish manufacturers build nowadays. Fiddly electronics and can-bus wiring and modules. The late 80's to mid 90's where the best years for vehicle reliability. The reason I chose the jk over the tj or lj is the long wheelbase and super strong frame. I hated the CRD engine. I lost count of how many times it overboosted due to sticking vgt turbo vanes and left me rolling to a near stop on the highway while turning it of and back on in an attempt to reset limp mode. and hated getting diesel on my hands when filling up or working on it.

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Jiffy05

New member
I completely agree with you about modern technology with cars. I too am a fan of the older stuff. It is much easier to work on when something does break and much of it is more reliable.
 

JayKay

Caught the Bug
I dont consider this going backwards. I hate modern technology and the minimalist rubbish manufacturers build nowadays. Fiddly electronics and can-bus wiring and modules. The late 80's to mid 90's where the best years for vehicle reliability. The reason I chose the jk over the tj or lj is the long wheelbase and super strong frame. I hated the CRD engine. I lost count of how many times it overboosted due to sticking vgt turbo vanes and left me rolling to a near stop on the highway while turning it of and back on in an attempt to reset limp mode. and hated getting diesel on my hands when filling up or working on it.

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I hope you're not including the GM products of this era in your comment. Mid to late '80s and early '90s GM vehicles from this era were technically junk. Experimenting with on board computers, digital gauge displays, and push button accessories. Worst experiments ever! Now Jeeps on the other hand, putting a 4.0 in your JK is a great idea. You're putting an extremely reliable power plant in possibly the most practical SUV ever produced. :thumb:
 

dahreno

Banned
I don't consider it going backwards either. You are putting in a great engine that they should have never quit building. I'm interested in what smog regulations you have up there. In theory, the 3.8 put out a little more h/p and torque than the 4.0. I have owned both engines and I can't tell. It always felt to me that the 4.0 had more power. I would think you could feel the difference in what ever vehicle you put it in.
 

Jiffy05

New member
I don't consider it going backwards either. You are putting in a great engine that they should have never quit building. I'm interested in what smog regulations you have up there. In theory, the 3.8 put out a little more h/p and torque than the 4.0. I have owned both engines and I can't tell. It always felt to me that the 4.0 had more power. I would think you could feel the difference in what ever vehicle you put it in.

Only reason I say it is backwards is because the new technology that they are using for engines now. I also agree the 4.0 is a great engine and I wish the Wrangler still had it.
 

JKUndaunted

New member
The other reason for using the 4.0 is because Every job on this motor is simple! as soon as all the pulley brackets are removed its a walk in the park. Im not sure what's honna happen on my first MOT (inspection) will it have to conform to 1994 or 2007 regulations? I dont know but im sure it will be fine. My 91 xj has no CAT and a 2 1/4" cherry bomb, the guy at the garage cant believe how clean it is! I think I may have to stick a CAT on the jk to keep the Feds happy as they became mandatory in 1993.

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hinrichs

Caught the Bug
Very interesting swap for sure, hope you can get it inspected. going to run stand alone gauges or are you going to try and make the stock dash work?
 

JKUndaunted

New member
Probably gonna junk the gauges. Will make a panel to fit inside the dash cluster and have all gauges in there. Fuel gauge, oil pressure, transmission temp, voltage, rev counter and maybe a gps speedo.

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