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CJ7/YJ Hybrid 4.8 LS, Ton Swapped
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Discussion Starter · #1 ·
Hi All,

Here is the start of my CJ with tons and an LS. It's in the beginning stages, but I have most of the parts to complete the project. The frame and front clip are from an 84-85. The tub is from a YJ, but it was relatively rust free, so I couldn't pass it up for $100. 4:10 gears. 14 bolt full float rear. Using a passenger side drop GM front axle so I can use a Dana 300. Humvee rims and tires until I can afford something better. The fuel tank you see in the photo is for my tractor, it just fit nicely in the back of the jeep for storage.

I have a 4.8 with 175K on it, 4l60, advance adapters kit for Dana 300 twin stick. Engine is still sitting in my donor truck at the moment.

I am using CJ 2.5" leaf springs over the axle, so I've widened the leaf springs in the front to match the GM perches.

Hoping to get frame painted this week. It barely has surface rust on it. Unbelievable condition. After that I can set the engine on some custom mounts and mock up the driveline length. I have an aluminum radiator with a built in fan, and I'm hoping that will give me a few extra inches to work with.

Stay tuned for more.

4430282
 

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CJ7/YJ Hybrid 4.8 LS, Ton Swapped
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47 Posts
Discussion Starter · #3 ·
4475287

4.8 LS fits nicely.
 

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CJ7/YJ Hybrid 4.8 LS, Ton Swapped
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Discussion Starter · #4 ·
4475307

Painted the body and fenders rattle can to “match”
 

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CJ7/YJ Hybrid 4.8 LS, Ton Swapped
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Discussion Starter · #5 ·
4475310

custom bumper and my warn 10k on there. Had it out for a test ride, needs some steering adjustments still and top off of fluids.
 

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CJ7/YJ Hybrid 4.8 LS, Ton Swapped
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Discussion Starter · #6 · (Edited)
I've been working on this project in bursts. Then it sits for a few weeks before I build up the ambition to get going again.

The motor swap went well. I had to travel out to the west coast for family matters, and when I got back I discovered that my buddies had dropped the engine and transmission in while I was away. 😎

We got the 4L60 mated to the Dana 300, super easy thanks to the innovations at advance adapters. Their customer service department is excellent also.

A drop crossmember had to be fabricated due to the driveline changes. Since I ended up ditching the clutch fan to scoot the engine almost 5" closer to the grille the extra space gave me a nice driveshaft angle and acceptable length.

The 4.8 requires 50 psi of fuel pressure so I picked up an inline fuel pump from summit and a new YJ sending unit. I'm using a steel CJ tank, so I had to rotate it 180 degrees for the filler neck to line up with the YJ body, no big deal.

I'm using the YJ master Cylinder/booster and ran all new lines. The 14 bolt is drum brake now, will be converting to disc later on.

I'm still fighting with factory wiring and gauges, mostly because I want to save as much of the YJ dash for nostalgia purposes. I have a Bluetooth OBD port that shows all my readings on my iPad.

Most recent is a final exhaust system. I had the local muffler shop assemble everything. All custom bends, held up tight to the body for maximum clearance. 2.5" from both headers back to a 3" round FlowFX by flowmaster. Its obnoxiously loud, but it all goes straight out the back.
 

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CJ7/YJ Hybrid 4.8 LS, Ton Swapped
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Discussion Starter · #7 ·
Today I will be working on my steering. I have a 1 ton chevy steering box, wishbone on the drivers side. I just got my 4" drop pitman arm via UPS. Thanks boys in brown!

When steering left the body droops a bit before the wheels move, and I'm guessing it is because of the steep angle on the drag link. I don't want sway bars or a track bar. The suspension movement is stiff enough due to the leaf springs.
 

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CJ7/YJ Hybrid 4.8 LS, Ton Swapped
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Discussion Starter · #8 ·
4475329
This should do the job
 

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CJ7/YJ Hybrid 4.8 LS, Ton Swapped
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Discussion Starter · #9 ·
At a standstill for the moment. The drop pitman arm is great, but the distance to the knuckle is shorter than before.. I’ll need to cut 1” off each of my ends to make up for it. Unfortunately I’m out of grinding wheels, and out of steam today.
4475339
 

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CJ7/YJ Hybrid 4.8 LS, Ton Swapped
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Discussion Starter · #12 ·
4475471

New parts had to be modified. That’s what jeeps are about, right?
Even the steering wheel is straight!
 

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I'm looking at doing a similar build once my 4 cylinder dies. I've got a chevy 5.3 and a set of super duty axles sitting in my shed. How does it drive? is there anything you'd do differently?
 

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CJ7/YJ Hybrid 4.8 LS, Ton Swapped
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Discussion Starter · #14 ·
I'm looking at doing a similar build once my 4 cylinder dies. I've got a chevy 5.3 and a set of super duty axles sitting in my shed. How does it drive? is there anything you'd do differently?
It has a lot of power. It’ll be a huge difference from the 4 banger. You’ll just have to get used to that.

You can buy mounts that set the engine left or right to give the driveshaft some extra space. I don’t know how the factory gm t case will work, it’s big and has a long tail shaft. Advance Adapters hooked me up with the 4L60 to Dana 300 kit. They have one for the NP231 too since you’ve got a drivers drop axle.

Overall it drives ok. My steering was pretty loose, but I think I have that solved with my new parts. I was using mostly junk yard parts, and that saved me money but caused other headaches. Next time I build something it’ll be four linked with coil overs all around, I think my fabrication skills are good enough now. I’m not a hard core off-roader, but the ride quality will be a lot better than 4 leaf springs. Plus I could stretch out the wheelbase a bit more that way.
 

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I have a np231 that was recently rebuilt with a SYE, so that is what I plan on using for a tcase. I'll use the advanced adapter kit with a new input shaft.

I know it will never ride like a caddy with leafs, but I am just worried about large tires on such a short wheelbase. I've got 37s of my ford pickup, but that has an additional 40" on the wheelbase, so it feels a lot more stable. Motobuilt has a stretch kit that uses an xj leaf, but I think I'll try it out with the stock wheelbase first.

I'm in the same boat, I don't plan on doing hardcore wheeling with it. I just see a lot of mud and snow.

Did you take the runflats out of the tires?
 

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CJ7/YJ Hybrid 4.8 LS, Ton Swapped
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Discussion Starter · #17 ·
E17D1EC8-1AEF-433D-9DD7-573AB507D91B.jpeg 840F5F63-AB6C-41B3-809D-C2D8E23BA319.jpeg D061422F-661E-4F96-93BC-301B8188EBD1.jpeg

Here’s some interior shots. It’s not perfect, and someone stole the radio faceplate before I acquired the tub. Can’t hear it over the exhaust and tire noise anyway 😅

JBCustom Fab twin sticks, American Shifter on the trans. Gas pedal from a 90s Chevy. The YJ pedal had short linkage and that was an easy grab from my parts truck graveyard.

I’m going to weld the old clutch pedal to the brake pedal. I’m a left foot braker, a bad habit I know.
 

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Discussion Starter · #18 ·
4477038

Struggled all weekend with the steering arm. Guess I’ll let it soak for another day before I have to start beating again after work.
I’m still having issues with angle even after the pitman arm upgrade. I have a 4” lift arm coming, assuming I can get this thing off.

I also have a sway bar and disconnects on order. I didn’t want to go that route but the body roll is just a bit more than I like while driving, especially on crowned frost heave roads.
 

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Discussion Starter · #19 ·
image.jpg
success. All it needed was a good soak, heat and the BFH
 

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Discussion Starter · #20 ·
Had good progress last week/weekend. I went back to the flat pitman arm and used the 4” steering arm. Nice, flat drag link now. I’ll be returning the $117 drop pitman arm. 😬

I did a tape measurer alignment and I took it out for the first real road test. DEATH WOBBLE occurs at 25-30 mph, unprovoked, on any surface. I also have a brake issue. The drivers side front must not be grabbing because the rig pulls hard right when the brakes are applied.

I know the causes and remedies of death wobble. I’ve been there many times before on my old XJ and my YJ. Everything is new so it has to be something stupid. I’m getting a real allignment at my buddy’s shop this week, and I hope that cures it.

I also fought hard with my cooling system. The engine was overheating constantly despite ambient temperature less than 20°, a new radiator, thermostat, and water pump. Eventually after many cycles of purging the air from the system I got coolant flow and HEAT in my cab. That’s a necessity considering we have had 15° daytime highs here in Maine. 🥶

Yesterday, I was looking through my parts pile to see what could go back to the graveyard, and I tripped over an old driveshaft. Just for fun, I held it up in the Jeep and it was an exact fit for my front drive. It was meant to be. I threw some new ujoints on from the shelf and bolted it in. Of course I had to lock the hubs and go for a test!
4479340
 
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