Build-up: Jeep YJ w/ Isuzu diesel

[iroc86]

Ever since I bought my 1995 Jeep Wrangler five years ago, I've been planning on rebuilding it the "right" way. There really wasn't anything wrong with it, but my Jeep wasn't anything special --- just your ordinary, gutless, 2.5L YJ with 33s. I have to admit, despite the four-cylinder's lack of power, it was a capable machine off-road for what it was.

Here's what I'm working with:






I unofficially started this project back in 2003 with the purchase of an SM465 transmission and NP205 transfer case. I scored a sweet deal on eBay and just couldn't resist. It would be nice to have overdrive and a slightly better low range, but nobody can argue with the strength of this drivetrain.

My original plans involved the tried-and-true small block Chevy engine, but after learning a great deal about diesels, I changed my mind. I searched relentlessly for a Cummins 4BT, but ultimately I chose the Isuzu 4BD1/2-T. The Isuzu diesel doesn't produce as much torque as the Cummins, but it is much quieter and smoother. (Now that I've driven one, I can attest --- for a diesel, it's not too bad!) I've learned that repowering with a 4BD1/2-T is a fairly new thing, so we'll see what happens!

Along with the engine swap, I'm doing a couple other modifications. Here's the full list:

Engine: Isuzu 4BD2-T intercooled turobdiesel
Transmission: SM465 four-speed manual
Transfer Case: NP205, 1.96:1 low range
Front Axle: Dana 44 (1978 Jeep Wagoneer)
Rear Axle: Ford 8.8 (1993 Ford Explorer)
Suspension: Leaf springs, SOA
Tires: 35x12.50 to start

I'm also reinforcing the frame, redoing the entire wiring harness, installing a CJ-style dash, and repainting the body. In other words, I'm going to rebuild the whole freakin' thing. My plan is to have the Jeep roadworthy in four months. (But, as they say, "assume that it'll take twice and long and cost twice as much.") I'm trying to stay optimistic.

I started tearing everything apart for the rebuild. The body is unbolted and ready to come off the frame, but I want to keep it there until I figure out the driveline clearances.




Everything is gutted on the inside to make way for a new dash, wiring harness, and most importantly, spray-on bed liner.




Here is the SM465 and NP205 drivetrain. This picture was taken a few years ago and I've since rebuilt both of them.




For the front, I snagged a Dana 44 from a 1978 Jeep Wagoneer. The differential is on the passenger's side of the axle.




This is the Ford 8.8 I'm using for the rear. It has drum brakes, but I will be converting them over to discs. This axle is only two inches narrower than the Dana 44. After adding the appropriate bolt pattern adapters, they should be comparable in width.




Ahh yes, the box truck! I bought this out of Philadelphia last week. Never thought I'd own a box truck before, but hey, there's a first for everything. This GMC W4 tilt-cab is made by Isuzu and (surprise) has an Isuzu 4BD2-T diesel engine. It ran great on the way home, but it has some blow-by. With 221,000 miles on the clock, I'm not too surprised.




Here are a few pictures of the engine. Nothing special.






If all goes according to plan, I'll be removing the engine this weekend and test-fitting it into the Jeep's engine compartment. I haven't made (or bought) an Isuzu-to-Chevy bellhousing adapter yet, so it'll be a week or two until I can bolt up the transmission and see how it all fits together.

[navymark08]

Being just a little further in my swap than you are in yours, I'd say test fitting the engine alone won't get you too far. You won't really know how it will all fit until your drivetrain is all set up. I started the test fitting with my engine and transmission together only. I didn't make any considerable or notable conclusions about how it will fit until I hooked my transfer case up behind the tranny. Ever since I had it all hooked up, the guesswork is almost completely removed which will save you time and Tylenol

[wiggamoe]

Sounds like a great project. What are you doing about lockers?

When you are ready to remove that Dash, shoot me a PM. My spice dash is in rough shape. Do you still have the spice leather wrapped steering wheel?

[kpj]

What is the power output of the Izuzu? Sounds like a nice project.

[87JeepWrangler]

a little different. neat.


what are you gonna do with the box truck tho? are you gonna rebuild the motor at any point?

[wh0f4rted]

This is a pretty cool build!

I read up about the 4BT awhile back but I got scared because I know nothing about diesels. My major concern was turbo lag. And not to pee on your parade but it seems like you are putting a tank drive train on pow-pow-power wheels running gear. Even with the 6.55 1st wouldn’t you be better off with a lighter duty transfercase with a lower low range? Especially since your weak link will be the axles.

[iroc86]

Yeah, I don't really expect to solve a lot by test-fitting just the motor, but it'll give me an idea of the width and height in relation to the engine compartment. And it'll look cool. navymark08, I'm glad to hear that once I get the drivetrain figured out, everything else will fall into place. Thanks!

I'm going to run selectable lockers front and rear --- the Eaton ELocker. It's very similar to the ARB air locker, but the ELocker is activated electromagnetically. (It's not the same thing as the Detroit Electrac; the ELocker acts as an open diff when disengaged.) Here in Pittsburgh, we see a good amount of snow each winter and I want to retain control on covered roads, so a selectable locker is the only choice.

From what I've read, the Isuzu 4BD2-T outputs 135 hp @ 2800 rpm and 255 ft-lbs @ 1900 rpm. It's intercooled, but uses indirect injection. The older version, the 4BD1-T, is direct injected but isn't quite as powerful. For comparison, the Cummins 4BT produces 105 hp @ 2500 rpm and 265 ft-lbs @ 1800 rpm. All in all, they're pretty close --- but the Isuzu doesn't sound like a tractor! I don't think turbo lag is going to be much of an issue. The box truck didn't come off the line quickly, but when it got goin', it was goin'.

The motor runs strong, but it could use a little work. I haven't checked the compression yet, but I think it's going to need a rebuild. There's a decent amount of blow-by and it doesn't start in cold weather unless it's plugged in. (The glow plugs are probably shot, though.)

As for the truck body, I'm probably going to sell it without an engine. I don't know the market for these things, but it really is a nice truck. I almost feel bad pulling the motor out of it... the body still has a lot of life.

Oh, and I was waiting for someone to comment on my axle choice . I know the D44 and 8.8 aren't the best axles for this application, but it comes down to a matter of convenience right now. Both of these axles will fit under my YJ without narrowing, which saves me a great deal of time. I'm also keeping the Jeep street-legal, so that prevents me from running full-width axles. (I've already gotten tickets for fender flares and tire size.) It won't be hard to add D60s later on, if it's necessary. These axles should easily handle 35s, even with the diesel.

As for the transfer case, I'm honestly not sure how the torque of a diesel will affect a light-duty case. I don't have to worry about the NP205 being a weak link. Remember, the torque from a diesel comes on hard from idle, so you don't need as much gearing to get the engine into its powerband. Of course, torque multiplication is still important.

Thanks for taking a look!

[navymark08]

If you can't sell the truck without the motor. Try and sell the box - I hear they fetch good money. If you can't sell that, you can either cut it up and sell it for scrap aluminum or make a shed out of it .

I'd never make a shed out of it, but apparently it's a popular thing in some places. When I was looking for a 4BT, I thought about getting a step van with one in it. I never found one, but I ended up buying a 4BTA for my TJ conversion from a guy who bought the van just to make a shed out of it. Sounds bizarre, I know, but some people are weird like that

[iroc86]

He bought the van to make a shed? Wow. One man's junk is another man's treasure... hahaha.

I'm not sure what aluminum is going for these days, but you're right about scrapping it. That box has got to be worth something.

GM also used to put small blocks in these tilt-cab trucks, so that's close to a bolt-in. Maybe someone would buy it for that.

[Dude_Jeep]

Wow weird. Never would have thunk it.

Why did you go with the older izuzu engine?

[iroc86]

Originally Posted by Dude_Jeep

Why did you go with the older izuzu engine?

I'm not sure I understand what you mean. The 4BD2-T was used from '92 to '97, and the 4BD1-T was used from '86 to '91. Both motors are near identical, but the newer version is intercooled and is not directly injected.

I would have been happy with either one. The tilt-cab truck I came across just happened to be a '95 with the intercooled engine, and the price was right.

[iroc86]

My friends and I pulled the engine today. It actually came out easier than I had expected, but man, is that thing heavy.

Separating the engine from the body was straightforward, just like any other vehicle. I didn't feel like fussing with exhaust bolts, so I just cut the pipe below the turbo.




Let the digging begin...




The engine slid right off the transmission.




My friend's backhoe saved us a bunch of aggravation. This sure beats using an engine hoist!




Here's one last picture hanging from the hoist in my garage. Tomorrow I'm going to put the motor on the stand and clean it up a bit. Preliminary measurements show that it's only about two inches larger, in every direction, than the 2.5L gas engine I'm replacing.

[silvergreentj]

looks good. Keep us updated on the finish

[guidolyons]

Cool Did you find an adapter for the SAE3 to GM pattern?

I just saw a link recently to a website that sold (NPR box van) 4BD2 conversion kits..but a quick search I couldn't find it. I think the guy put it in a brand new Chevy Silverado.
I'll see if I can find it...

[iroc86]

guidolyons, that website was http://www.isuzudieselswapper.com/. His name is Dave and he sells an Isuzu-to-Chevy bellhousing adapter, plus the spacer for the flywheel. (The bolt pattern actually isn't SAE 3, but it's close. It's some kind of metric version.)

I was going to make my own adapter, as I have access to a prototype machine shop at my school. For the amount of the time that I'd spend with the CMM trying to coordinate the two bolt patterns, plus machine time and material costs, it's probably easier to just buy the darned thing. I can make it, but I don't necessarily want to make it!

[guidolyons]

Originally Posted by guidolyons

Cool Did you find an adapter for the SAE3 to GM pattern?

I just saw a link recently to a website that sold (NPR box van) 4BD2 conversion kits..but a quick search I couldn't find it. I think the guy put it in a brand new Chevy Silverado.
I'll see if I can find it...

Originally Posted by iroc86

guidolyons, that website was http://www.isuzudieselswapper.com/. His name is Dave and he sells an Isuzu-to-Chevy bellhousing adapter, plus the spacer for the flywheel. (The bolt pattern actually isn't SAE 3, but it's close. It's some kind of metric version.)

I was going to make my own adapter, as I have access to a prototype machine shop at my school. For the amount of the time that I'd spend with the CMM trying to coordinate the two bolt patterns, plus machine time and material costs, it's probably easier to just buy the darned thing. I can make it, but I don't necessarily want to make it!

Yup, that's the one I was thinking of. I knew it was something simple, I don't know why I couldn't find it earlier. I assume your donor truck has the manual transmission? It looks like his kit converts to GM auto, but uses the manual flywheel. I wonder if he would just sell the adapter ring, and you could use the isuzu flywheel & pressure plate with a Chevy disc to match the SM465 10 spline input. Pilot bearing size?

At some point I'd like to swap a diesel into my Scout 80, 1st choice is a Cummins 4BT, but I had also been looking at the Isuzu NPR 4BD2T but was concerned about getting the transmission I wanted bolted behind it. There was a guy on here awhile back that was trying a Mitsu box van diesel swap but ended up selling it, when he couldn't figure how to get the engine/tranny to work,... I think it was an SAE#3. Now, I wonder if it was the same as the Isuzu?

Oh yeah...that D44 and 8.8 will go

but they should get you rolling. If you take it easy.

[Po' riggity]

Cool build.. I love diesel yj builds.. great idea!
Scott

[iroc86]

Actually, Dave's kit can go either automatic or manual. His bellhousing ring and flywheel adapter essentially turn the back of the Isuzu into a Chevy V8 --- anything that'll work on a Chevy will work here. The only downside is that you have two flywheels (Isuzu + Chevy), but Dave assures me there are no side effects.

Unfortunately, the two flywheels are necessary. You need the Isuzu because it has the teeth for the starter. It's not possible to use a Chevy clutch disc because the bellhousing ring spaces everything out a couple inches, and the transmission input shaft isn't long enough.

I used to be afraid of these bellhousing adapters, but now that I understand how they work, it's no big deal. (Let's hope I don't eat my words!) All you're doing is adapting and spacing.

The Cummins is an awesome choice because it usually has the Chevy adapter. That was my first choice, too... but after driving an Isuzu, I'm sold on the 4BD1/2-T. It's just so smooth for a diesel. Watch this video from YouTube. Two guys start up a 4BD1-T on the shop floor and it just sits there, purring along. No vibrations, nothing. I bet the Cummins would be bouncing all over the place .

[jeepcj]

what about leaveing in the Isuzu trans then a small jack shaft the a divorsed transfercase? Just make your wheel base a bit longer?

[iroc86]

Originally Posted by jeepcj

what about leaveing in the Isuzu trans then a small jack shaft the a divorsed transfercase? Just make your wheel base a bit longer?

My Isuzu diesel was mated to a four-speed automatic, and I want a manual transmission. Plus, that thing is HUGE. Even with a longer wheelbase, it'd be way too long for a YJ. A pickup truck could handle it with no problem, though.

[1speedlos@gmail.com]

Like so many others, I've been eyeballing a 4BT for a swap in my TJ, but it's good to know that someone else is Doing it a bit differently. I've driven service trucks with this engine, and you're right- it's amazingly smooth-running for a diesel.
Good to know that this is an option. Any idea what the 4BD2 weighs in at? I couldn't find any engine weights listed on Isuzu's Commercial Vehicle site...
Looking forward to following your build, and being a bit envious of your "engine hoist".

Los

[FF3PM]

Nice build so far.

[wh0f4rted]

Originally Posted by iroc86

Oh, and I was waiting for someone to comment on my axle choice .
Thanks for taking a look!

Oh no buddy I didn't mean to rip on ya. This is a pretty cool build either way. Its nice! I like!

[Shaggygto]

what are you doing about wiring?

[iroc86]

Thanks guys! No harm done, wh0f4rted... I was just kiddin', too!

I can't take complete credit for coming up with the Isuzu diesel idea, as it's been discussed quite a bit in the past. The Land Cruiser guys seem to like them, but not many people have put this diesel in SWB Jeeps (based upon my research, anyway). The following threads have been invaluable for obtaining information on the 4BD1/2-T:

isuzu 4BD1T swap?! at IH8MUD

Isuzu 4BD-1T / NPR Box Truck Revisited... on PBB

The 4BD1/2-T forum at 4btswaps.com

Some of the information is redundant and/or updated throughout the threads, so I suggest reading them in their entirety... even if it takes all night!

Los, one of the posters at IH8MUD weighted a basically complete 4BD1-T to 785 pounds. That's probably comparable to the 4BD2-T, but don't forget to add another 20 pounds or so for the 2's intercooler.

That "engine hoist" was AWESOME. Funny story: We used the bucket to lift the engine from the chassis, and the front end loader to raise it into the pickup truck bed. We could only get so close to the box truck to ensure the boom had enough movement to swing around and pick up the engine. During this process, I was standing on the front scoop with two other people to act as a counterweight for the engine. Despite the extra leverage, the front of the backhoe suddenly lifted about four feet as my friend worked the bucket... the engine is THAT heavy. I think I had to check my pants after that one!

Shaggygto, I'm rewiring the Jeep myself. I know that wiring jobs strike fear into the hearts of many, but there isn't much to a diesel --- at least not these older models. It all comes down to the starter, fuel injector solenoid, and glow plug timer. The wiring diagram fits on one page. Since I'm doing a custom dash, I figured it'd be easier to rewire everything since I can remove a lot of the gas engine stuff. That's going to make it slightly more complicated, but if you're just doing the engine, there's nothing to it.