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Oscar the TJ gets a CUMMINS

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4bt cummins tj
149K views 545 replies 89 participants last post by  TN-Mike-89YJ 
#1 ·
As the title suggests I am assembling the parts to put a Cummins 4BT in my 98 TJ. I Have been reserved in starting a build thread just because I don't want this thread to become one which is started and then all of a sudden it just magically stops.

I look forward to sharing the information which I have learned and intend this thread to be a guide for people who also want their JEEP to roll some coal.

A little background on the Jeep first. I bought my TJ bone stock three years ago for 5K from a grandfather who was saving the Jeep for his grandson. As life would have it the grandson wanted NOTHING to do with Jeeps because they are loud, ride like log wagons and bad gas mileage. Personally I was happy the kid had a terrible opinion because I got the Jeep for a decent price.

I couldn't wait to start turning the wrenches on the Jeep which my wife named Oscar because of the forest green color and she thinks that the Jeep makes me grouchy when I work on it. The first on the to do list was a Rough Country 2.5 inch suspension lift with the 3/4 inch poly spacer, Advanced Adapters slip yoke eliminator, Tom Woods drive shaft ,stinger front bumper from TKH fab and 33x12.50x 15 BFG muddterrians on Cragar Soft 8's.

The Jeep has been pretty much this way until about the last year when I upgraded the rear Dana 35 to a Ford 8.8 limited slip and a front Dana 30 high pinion which is Aussie locked. Also re geared the axles to 4.10s. This pretty much brings the mod list to current minus small things like cab lights, and Raptor lining the tub.

http://i1223.photobucket.com/albums/dd506/10-3-tj/0524121348.jpg
http://i1223.photobucket.com/albums/dd506/10-3-tj/0524121348a.jpg
http://i1223.photobucket.com/albums/dd506/10-3-tj/0524121348c.jpg

Approximately 5 months ago my stock 4.0 engine has been making some killer sounds. The lifters are crazy noisy ( which I know is common) I have been getting a very bad knock on the rear two cylinders. It was suggested by a couple guys at work that I was hearing piston slap. I dunno though they couldn't explain what piston slap was.. Also the engine has been running junky and honestly I was tired of chasing problems with the engine. I would get one issue fixed which led to another.

I contemplated doing a stroker and V8 and have been running through many pages of information on everything. I finally made my decision on a Cummins 4BT diesel. I will be very honest, the diesel is not the cheapest engine swap to do but for what I wanted the Jeep to be in the long run, the diesel was best choice.

I contacted Jeff Daniels Jeep (http://www.jeffdanielsjeeps.com) and spoke endlessly with Dan and Sean. Both Dan and Sean own the company and are EXTREMELY polite, personal and educated in putting Cummins in YJ's TJ's and even JK's. I was very impressed with both of their knowledge bases of the Cummins engine and Jeeps.

Dan found this engine for me.
http://i1223.photobucket.com/albums/dd506/10-3-tj/IMG00700-20120612-1708.jpg

This engine is from a bread truck and is 80,000 miles fresh from a Cummins Recon. The engine has an H1C turbo and is non-wastegated.

www.jeffdanielsjeeps.com
 
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#81 ·
PAPITT.

You make a great point about the exhaust pipe. I will take that advice and leave it alone until it causes me a problem. I also have considered the H1 intake idea and i am going to research that idea more right now.

On to the updates

I started this morning at 6:45am i couldnt sleep because i was so excited about taking the jeep apart.

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Here i have the grill off and starting on the radiator.

Next up after the radiator was the passenger side fender.

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#85 ·
#82 ·
Also i dropped my bellhousing off at the machine shop and had them soak and clean it.

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Then added a little Cummins beige

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I took tbe following picture cause it made it look like the jeep was bleeding... its atf which I was running in my power steering.. no real good reason why i was using atf rather than power steering fluid .

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#86 ·
I love this build man. I helped one of my buddies do a 4BT Cummins swap in a 88 YJ with NV4500 tranny swap too. It is an amazing setup. Great progress so far. Keep up the good work! :2thumbsup:

And I also helped another one of my buddies put a 12Valve 6BT Cummins into a J-20 jeep truck. Both are amazing and the J-20 is pretty much one of a kind(Around here anyways)
 
#87 ·
Krasnake. Thanks for the encouragment. Does your buddy have any vidros on youtube of his J-20?

This morning i made some good progress. I have entire wire harness off the engine and the engine is ready to pull. Only thing is, i am not exactly sure where to hook my chain to the engine to pull it. Any suggestion.. i plan on selling the engine so i dont want to take it apart much to pull.

Also got the driver side fender off

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Aftet that i got my clutch master cyclinder all hook up with my clutch fork and ready to go on.

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And then the brown truck man brought me some BLING. this will be the only chrome on the jeep.

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More updates tomorrow..
 
#94 ·
Krasnake. Thanks for the encouragment. Does your buddy have any vidros on youtube of his J-20?

This morning i made some good progress. I have entire wire harness off the engine and the engine is ready to pull. Only thing is, i am not exactly sure where to hook my chain to the engine to pull it. Any suggestion.. i plan on selling the engine so i dont want to take it apart much to pull.

Also got the driver side fender off

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Aftet that i got my clutch master cyclinder all hook up with my clutch fork and ready to go on.

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And then the brown truck man brought me some BLING. this will be the only chrome on the jeep.

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More updates tomorrow..
No he doesn't. I wish he did though, I will propose that idea to him the next time I see him.
 
#91 ·
Ksilovich.. Thanks. I was looking at those studs today and was worried about lifting the engine out with the chains on the same side. But your picture shows it perfect. That is exactly what I will do. Was it hard to pull it out? I dont really have any help in the mornings and dont want to do it at night.

Pappitt.. I will post a picture of the decals and some sort of refrence. I bought them off of ebay for somthing like 60 bucks shipped. I bought them from an ebay seller named smity2 They were titled NEW 2006-20012 Dodge Ram Cummins turbo diesel fender emblem.
 
#92 ·
Papitt...I saw sticker the other day on a first gen Dodge truck it said " I'd rather be cummin than strokin " I thought that was awesome. tacky but awesome. There is no way my better half would allow that on anything I drive.
 
#95 ·
JKNATE... yeah thats what i meant. Like i tell the guys i work with, dont listen to what i say, listen to what i mean . :)

Today i didnt get much done. I hooked my pull chain to the engine and that was all.
 
#96 ·
Here is a refrence of the size of the fender emblem .

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#98 ·
Well fella's today i didnt get much done. I managed to get the engine un bolted from the tranny. The only bolts holding the engine in are the motor mounts. Tomorrow morning i plan on pulling it out.
 
#100 ·
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The engine finally gave up the ghost. It was a PITA to get it out. I will be the first to admit this is the deepest i have ever been in my Jeep.

Now on to the bellhousing, engine mounts and cutting out my old exhaust. Which isnt that old :(
 
#101 ·
For the mechanics who do this work on a daily basis you are strong men. I think every inch of my body aches from turning wrenches, prying on stuff, busting knuckles and so on.. honestly though if it was easy everyone would do it.

I think it was President JFK thats said " we do things not because they are easy, but because they are hard" . Now he was talking about going to the moon.... not putting a cummins in his Jeep, but thats how i feel about it..
 
#103 ·
Cymmins5552

What did you do to correct the starter interference? I was looking at mine and I could see the passenger side upper control arm may be an issue with my starter on the 4bt.
 
#104 ·
So i have gotten all of the taking apart done and have started putting pieces back on.

First is the empty engine bay showing the bellhousing which needed removing.

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After that i needed to take the center of the transmission off in order to fit the bell housing adapter.

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After i got that piece off i cleaned it well with a razor blade and put new gasket maker down

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Then i installed the oil seal on the adapter plate

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After that i put the adapter on the transmisson and bolted it back down. I also installed the piece which the pilot bearing rides on.

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I also hooked up my stainless steel braided line for the clutch slave cylinder.

I also have the stock exhaust ready to be cut out.
 
#105 ·
After feeling like i got a lot accomplished today i thought why nit do the body lift also. So i went back out and started on the passenger side. Passenger side webt in like a dream. Maybe took 25 minutes.

Switch to driver side. Nope not happening. I broke three bolts and one came out. Thankfully the one that came out was in the back.

I think i am going to cut the body channel out from the bottom and drill the spot welds. Replace the damage. I am not going to start that until the cummins is in and running.
 
#106 ·
I think i am going to cut the body channel out from the bottom and drill the spot welds. Replace the damage. I am not going to start that until the cummins is in and running.
Before I ask my 2 questions I must first say you are doing something I really love and have always wanted to do. I almost bought a TJ with a 4bt already in but decided I couldnt drive someone elses art work. EXCELLENT JOB!

First question: With half the body lift in isn't that going to make it challenging to allign everything? I have done swaps in muscle cars, compacts, and trucks and I know doing them your pushing and prying to fit it sometimes.

second question: How are you running the exhaust? I'm know expert in 4Bt's in Jeeps so I don't know what you can fit and what you can't, so I guess the second part of my question is what are your restrictions?

Sorry for the long post I just like to learn :2thumbsup:
 
#107 ·
I can't imagine Oscar would drive anything but a diesel.

Great start to a grouchy build. I like your attention to detail. :highfive:

Wish I would have had the time to really pay attention to the little stuff when I did mine. Maybe I'll paint the next engine I put in mine. I have had so many fluid leaks in my build that I would have been very grouchy if I would have really cleaned mine up and then coated it in every fluid the jeep has.

Really like that you'll be able to run stock gauges. That is awesome!
I'll be watching this one!

Welcome to the oil burner club! :cheers2:
 
#108 ·
Okay, today I got a lot done.

First Cowboyup94 ask as many questions as you can think of. Doesnt bother me at all. I wanted this thread to be instructional and convince normal everyday guys that they can do this swap. You were absolutely correct when you asked about finishing the Jeep with half the body lift in. I thought about it all night and after sleeping on it I finished the body lift today. I was able to salvage a bolt which i thought was a gonner, so only two bolts broke and are needing repair. The Jeep now sits one inch higher everywhere :) Good Advice sir!!

Second question was about the exhaust. Jeff daniels sells an entire stainless steel exahust for folks who have inspections or want the stock look. However I am planning on running 2.5 steel pipe out of the turbo down to approxmiately the oil pan where it will turn 90 degrees and expand to a 4 inch pipe and exit from my fender. The 4 inch pipe will run through the battery box support and then exit. After exiting the fender the pipe will run straight up as a stack and then have a 45 degree bend to the rear and side at the top. It will look very similiar to Garrets Diesel Jeep. search Garrets diesel jeep on youtube and thats what it will look like, only I am going to do either black chrome or powder coat flat black.

Now the legallity of the exhaust is simple... its not.. I am willing to take my chances. Its gonna be loud and smokey..just how a diesel should be.
 
#120 ·
Okay, today I got a lot done.

First Cowboyup94 ask as many questions as you can think of. Doesnt bother me at all. I wanted this thread to be instructional and convince normal everyday guys that they can do this swap. You were absolutely correct when you asked about finishing the Jeep with half the body lift in. I thought about it all night and after sleeping on it I finished the body lift today. I was able to salvage a bolt which i thought was a gonner, so only two bolts broke and are needing repair. The Jeep now sits one inch higher everywhere :) Good Advice sir!!

Now the legallity of the exhaust is simple... its not.. I am willing to take my chances. Its gonna be loud and smokey..just how a diesel should be.
One inch? Is that all? Do you plan on cutting the tub at all?
 
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