4bt motor swap in a 2008 Jeep JKUR

[ERICON18]

Im thinking about swapping my motor with my taxes. Curious if anyone has done this. If so comments, tips, and reviews would be much appreciated.

 

[Greg]

I think that if you're asking about a 4BT swap, its already far over your head. Not trying to be negative, but being honest.

Are you planning on doing it all yourself? Have experience with engine swaps? Do you have a massive budget? I would plan for at least double what you think it will cost.

You'll need a transmission that's capable of handling massive torque, a 1/2 ton truck trans wont last IMO.

 

[ERICON18]

Good friend of mine will be doing the work (lots of experiance)... many of the motors I have been looking at have transmissions. Many options..

 

[Greg]

Most of the transmissions that come with 4BT's don't have overdrive, so you will need a new transmission... and an adapter for that transmission. I would suggest an NV4500, myself. If you want an automatic, IMO your best bet would be a rebuilt 4L80E... and you'll need a standalone controller for it.

Do you realize how loud 4BT's are and how much they shake? Driving one often wouldn't be fun, IMO. On top of that, they're VERY tall and heavy. You will need to plan you suspension changes very well, those engines will require that you have at least 4" of lift to clear the oil pan and IIRC the 4BT's weigh around 750-800#'s, which is probably twice the weight of your 3.8l engine.

You will need to gear it for the engine, meaning you will need a transmission with a high OD ratio. Those engines have a very narrow operating range and peak torque is around 1800 RPM, so you'll need to plan carefully as far as axle ratio, tire size, highway cruising RPM, etc.

 

[ERICON18]

Thank you, all this will be considered

 

[Greg]

Your JK is a Rubicon, correct? So it has factory 4.10 gears? Those are pretty steep for a 4BT for sure. You need to know what size what tires you're planning to run. Lets run some numbers and get an idea of what you need...

Using this gearing calculator... - http://www.planet4x4.net/forums/calculator.php

If you use a NV4500, they have a .73 OD ratio. Say you step up to 37's and are shooting for 1800 RPM... your ideal axle ratio looks to be 3.55's. If you run higher cruising RPM with a diesel, your fuel mileage goes down considerably and you'll be spinning the engine higher than it likes. Do your best to shoot for the ideal cruising RPM.

 

[RockChucker]

seems like bruiser conversions down in clearwater florida has done these. might give them a call

edit.

yep. Pretty expensive though.

http://www.bruiserconversions.com/builders-conversion-kit/

 

[ERICON18]

Rockchucker, thank you.... Greg, my goal is 39.5" tires with a total lift of 6". Already planning on going to 60 rock jocks front n rear. Was planning on re gearing for optimal mpg's.

 

[Greg]

Rockchucker, thank you.... Greg, my goal is 39.5" tires with a total lift of 6". Already planning on going to 60 rock jocks front n rear. Was planning on re gearing for optimal mpg's.

Bruiser does sell that list of parts Dave linked to, which would probably save you a lot of headache in terms of motor mounts, A/C, etc, etc.

If you're planning on 40's, then 4.10 gears are about right.... a .73 OD ratio with 40's and 4.10's puts your cruising RPM right at 1880 @ 75 MPH.

Usually 4BT's aren't intercooled, I would highly suggest adding an intercooler and a better turbo.

 

[UNSTUCK]

seems like bruiser conversions down in clearwater florida has done these. might give them a call

edit.

yep. Pretty expensive though.

http://www.bruiserconversions.com/builders-conversion-kit/

For that price, you could run any LS motor. Is the 4bt a better choice then that, seeing as how it's not street legal and the ls can be?

 

[rholbrook]

I saw this at AEV in Missoula a couple of years ago. Bitching is all I have to say about it
http://www.dieselpowermag.com/features/0803dp_2007_diesel_jeep_wrangler_rubicon_jk/viewall.html

http://www.fourwheeler.com/project-vehicles/131-0710-ua-2007-jeep-jk-wrangler-diesel-engine/

 

[corbin.black]

For that price, you could run any LS motor. Is the 4bt a better choice then that, seeing as how it's not street legal and the ls can be?

what makes it not street legal? just curious

 

[RockChucker]

what makes it not street legal? just curious

Seems like I read when doing all my engine swap research that you aren't allowed to change the fuel requirement of the vehicle. Seems like it is because diesel has a different emission test?

But. Technically according to the guys down at the IM Tech center in Murray, it is illegal to change the engine to anything at all that wasn't offered in that vehicle from the factory. Some federal regulation I guess. Then they promptly looked my jeep over, drooled a bit and showed me pics of their project cars, passed my emissions test and sent me on my way. :greg:

Oh and if you really wanna spend lots of money on an engine swap, bag the 4bt. It's cool because it's different. But you can have way more horse power and probably similar gas mileage if you can keep your foot out of it with a warmed up L92 or LS3. Not to mention a lot easier packaging. You ought to give Dave Ostermiller up at Novak a call and ask him about his 6.2L JK with 37s, 4.10s and 6L80e trans. You might just change your mind...

 

[UNSTUCK]

what makes it not street legal? just curious

Says off road use only on bruiser conversions web site right under their price. The fuel requirement thing might be an issue. I would also guess they have some computer issues keeping lights on. AEV's conversion got all the lights off, but I"m guessing that would be a bit easier to do with a 5.9 cummins from a dodge then it would a 4bt.

For that investment, I would want it just about 50 state legal, so resale would be possible down the road.

 

[skippy]

Not to mention the 4bt is a turd of a motor, 30 year old technology is not something I would install in my JKU

 

[corbin.black]

I guess it just all depends on who you have inspect your vehicle. we have an 80's gmc Sierra pickup with a 4bt in it and it's register and street legal in Colorado. I've thought about doing a cummins swap in one of my TJ's but mostly just because I thought it would be cool. the 4bt's are stupid easy to swap into an older vehicle but I think it would be a nightmare to work in a jk. the 4bt only takes 5 wires to run but weighs 745 lbs. I think an LS is the way to go especially in a jk.

 

[Tacoma]

What's the point of this swap? 4bts have a very limited rpm range, heavy, loud, shake with or without the expensive counterbalance shaft and/or liquid-filled mounts, don't make THAT much power or torque, and require a host of other modifications that multiply the swap cost.

But hey! You can probably get in a magazine or something.

 

[gijohn40]

the reason that most people put hemi's in their JK's is because of the wiring system... I believe the new jeeps have the caan system and trying to make the gauges work with anything else is a nightmare in itself... the hemi runs off the caan system and makes it stupid easy to wire to the gauges...

Find a 6.2 hemi and you will have the fun you want... and be street legal with working gauges!

 

[UNSTUCK]

I guess it just all depends on who you have inspect your vehicle. we have an 80's gmc Sierra pickup with a 4bt in it and it's register and street legal in Colorado. I've thought about doing a cummins swap in one of my TJ's but mostly just because I thought it would be cool. the 4bt's are stupid easy to swap into an older vehicle but I think it would be a nightmare to work in a jk. the 4bt only takes 5 wires to run but weighs 745 lbs. I think an LS is the way to go especially in a jk.

Your're right. An 80's Sierra is very similar to an 08 JK. Well at least they both have an 8 in their model year.

It doesn't make a bit of difference who does the inspection, or how much you pay them. If it's not legal and you run it, any cop that knows better can have it towed away. What would you do then? You have how much money tied up in a jeep that is worthless.

 

[N-Smooth]

I agree with the question of why??? Besides all the potential problems with legality, a newer v8 just seems like it would do everything better and it might even be cheaper.

Are 4BT's neat? Sure. I just think they belong in older rigs.