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Modernizing a Classic Fullsize Jeep’s Drivetrain, Axles, and Interior

Recapping how we built this 1968 Jeep J2000 pickup.

I recapped some of the highlights from the buildup of my 1953 Willys DJ-3A, aka the Hazel Flattie, by going through some of the old buildup story photos that either never appeared online or that are buried somewhere in the pre-SEO world of creative wring that the Google bots don't tend to scrape into the first page or three of search results. The info is out there on fourwheeler.com but without all the nice keywords that make it easy for you to find. I wrapped it all into a recap story you can read here that resonated well with the online audience. So well, in fact, that here we go again with a recap of my 1968 J2000 pickup that I purchased back in the late spring of 2008 for $800 and spent roughly the next year modernizing the axles, steering, drivetrain, and interior in the pages of Jp magazine. I called it Project J2008, with the premise that I was building what we (at the time) would like a new Jeep pickup to be. So here's a brief recap of the articles, some of which still appear online at fourwheeler.com if you search, "Project J2008."

 

Jeep J2000 Purchase

Before online sale sites like Craigslist went to the dogs, I used to spend a lot of time browsing potential Jeep purchases. I had a litany of keywords all lined up and was pretty adept at finding screaming bargains. When I stumbled across this ad for a 1968 J2000 pickup with a running 232 inline-six, T14, Dana 20, and drum brakes, I jumped at the seller's $800 price and hoofed it from my home in San Diego up to Santa Clarita with my trailer as fast as I could get there. After forking over the money and collecting the paperwork, only then did I bother to fire up the engine to load it onto my trailer and noted immediately the clutch throwout bearing squealed like a stuck pig unless you kept a slight amount of pressure on it via the clutch pedal. The other thing I noticed was the engine oil pressure was almost zero. Regardless, I drove it onto my trailer deck, strapped it down, and dragged it home for a once-over.

 

Jeep J2000 Suspension

After unloading the Jeep, I pulled it up to my garage. The front suspension had lift blocks inserted between the springs and axle. That's a huge no-no and can be super dangerous, so I wasn't even considering driving it until I yanked them out. I jacked the front off the ground to check some play in the driver-side front tire that I noticed and discovered the upper kingpin on the Dana 44 front axle was completely wasted. I replaced it with a kingpin and bearing from an old Dana 27 I had lying around and continued my inspection.

I figured I'd just pull the lift blocks out and drive the Jeep with the little 31s, but when I removed the U-bolts to take out the blocks I found the centerpin had been snapped for some time. It's hard to believe somebody was driving this Jeep in this condition.

The rear spring packs weren't in bad shape, but the lift blocks weren't for this particular application and the blocks hung well past the spring pads on the early Dana 44 rear axle. I decided not to bother with the home-brewed 3-inch lift and put in an order for a new suspension that day.

There aren't too many lift options for these early post-mount fullsize Jeep suspensions. I found Hell Creek Suspension which had a 4-inch lift for this vehicle with full replacement front and rear spring packs. However, these trucks used several different spring eye post diameters, so before ordering you really need to remove your springs and measure the spring post diameter to make sure the new springs arrive with the right bushings.

The new Hell Creek Suspension springs showed up a couple weeks later, and I liked the look of what I saw. There would be no need for any kind of lift blocks or other shenanigans.

The front Hell Creek 4-inch springs dropped right into place. It's not good practice, but I reused the front U-bolts, which are a weirdo size and not commonly available. If I were retaining the stock Dana 44 front, I would've had a new set of custom U-bolts made, but since I was planning an axle swap I figured they'd do for a short while. I had an old set of Superlift shocks for a Wrangler project in the shed that wound up fitting the front perfectly.

I got the rear 4-inch Hell Creek springs installed, and once again a set of Superlift shocks intended for use on an old Wrangler project I had built were a perfect fit. Goes to show, never throw anything out if you're a Jeep hoarder. I replaced the dry-rotted 31-inch rubber for some 33x12.50R15 Pro Comp tires on 15x8 steel wheels and drove the Jeep around SoCal for a few months while I gathered parts and pieces for the axle and drivetrain swap.

 

Updated Dana 44 Axles Installed in Classic Fullsize Jeep

A couple years prior to my purchase of this 1968, John Cappa had put a pair of Rockwell 2.5-ton axles under his 1973 Jeep J2000 pickup. The rear axle out of his "Project Hot Dog" pickup was a good 30-spline Dana 44 that would be a bolt-in replacement for the weaker two-piece-shaft Dana 44 in my '68. I grabbed the rear axle from Cappa and sourced a Dana 44 front from a Dodge W-150 pickup and dragged them all down to MIT (Mechanically Inclined Technicians) in El Cajon, California, to be regeared and installed in the truck.

The factory axles in my '68 were loaded with 4.27 gearing. With 33s and no overdrive, the freeway rpms buzzed a bit, but I was already planning my drivetrain swap. Had I gone for a V-8, I would've regeared the new axles at 4.10 or maybe even 3.73, but my plans called for another inline-six, so to maintain good pulling power on grades, I went with 4.56 gears. Since this truck wasn't intended to be a rockcrawler but I didn't want to give up excellent off-road traction, I selected a pair of Eaton TrueTrac gear-driven limited-slip differentials. The TrueTrac is my all-time favorite limited slip, and I've used them in several of my project builds. It's always my go-to differential for any application that doesn't require a true locker. With the gears loaded in the '73 housing, the "new" rear axle bolted right in place of the factory '68 Dana 44. The rear brake lines and E-brake cables even hooked right up.

Rather than trailer it, I drove the truck down to the shop for the axle swap, which meant I'd need to address all the little things like steering linkage and brake lines before I was able to drive home post-swap. The stock steering linkage tie-rod ends were too small to fit the Dodge knuckles, so before I brought the axles down to MIT to be regeared and installed, I popped the passenger-side knuckle off my "new" '83 Dodge Dana 44 front axle and brought it up to Dynatrac in Huntington Beach, California, to be machined to accept a crossover steering arm. With the machined work complete, I ordered a steering arm and stud kit from Parts Mike. I also ordered tie rods and weld-in tie-rod bungs from Parts Mike so I could build my own steering linkage as the axle was getting installed.

The early FSJ spring location outside the framerials makes adding a newer fullsize axle relatively easy since the spring perches can be welded on outside of the pumpkin. The passenger-side-drop centersection on the Dodge axle is a near perfect fit. I ordered some new spring perches from Rubicon Express, including the offset one shown, which allowed the spring to just slightly overhang the rib on the centersection.

The new Parts Mike steering arm and linkage I built worked really well. My only regret was retapering the Dodge knuckles so the tie-rod mounted from below. I did that because I wasn't sure there'd be enough clearance for the spring pack with the tie rod mounted from the top. I was wrong.

After installing some new braided-steel brake lines to hook the original brake system to the Dodge disc calipers and tapering the stock manual steering pitman arm to accept the 1-ton Parts Mike tie-rod ends, I drove home and noticed the front brakes were dragging a bit. The next morning I popped the line for the front brakes off the factory drum/drum master cylinder (which is the rear-most fitting) and used a wood screw to pull the brass fitting ferrule out to expose the residual pressure valve. This maintains a bit of residual pressure in the system to help the drum brakes engage more quickly. However, disc brakes don't need as much pressure to actuate quickly, so if you're using a drum master in a disc brake application, the discs will drag unless the residual pressure valve is removed. I grabbed the residual pressure valve with a pair of pliers, removed it, and then reinstalled the brass fitting ferrule and reconnected the brake lines. After bleeding the system, the front brakes worked perfectly with no dragging at all.

 

Modern 4.0L Engine and Five-Speed Transmission Swap in Classic Jeep Pickup

The truth is, I was pretty happy with the original 232 engine. It provided adequate power, idled as smooth as glass, and was fairly economical. I hardly noticed the increase in engine speed in going from the factory 4.27 gears to 4.56s, but ultimately the nail in the 232's coffin was the super-low oil pressure. I was suspect at first, so I verified with two different mechanical oil pressure gauges on separate sending ports, but the engine made zero oil pressure on the gauge at idle and only showed a best of 15 psi at 3,300 rpm engine speeds. And that was after I filled the crankcase with straight 50W oil with two cans of STP oil additive! I contemplated keeping the engine and just rebuilding it, but after pricing out a valve job, new bearings, honing, and grinding the crank and everything else associated with a proper engine rebuild, I kept coming up well past the $500 cost of the 1991 XJ Cherokee take-out engine and harness I had a line on.

Even after sending the harness off to Hotwire Auto to be pared down and customized, the 4.0L swap came in only slightly more expensive than a full rebuild of the factory 232 and fuel system. So that's the way I went. I sent the factory harness off to Hotwire while I collected all the other parts I'd need to swap a Jeep inline-six for a Jeep inline-six.

As soon as the parts started rolling in, I parked the J2000 in front of my garage and started yanking the original drivetrain. The Dana 20 and T14 went to a buddy, and I wound up placing the old 232 on Craigslist for free. A guy from Los Angeles came down to grab it for a CJ restoration he was doing, so I like to think it's still out there powering a classic Jeep somewhere.

I got an NV3550 five-speed transmission that would make freeway driving a whole lot more pleasant with the 33s and 4.56 gears. The nice thing about the NV3550 is it'll bolt right to the 4.0L using stock components and is a great fit beneath the fullsize Jeep transmission cover. All you need to do is rework the location of the shifter opening in the transmission hump so it's farther back. My only real problem with using a modern Jeep transmission was the fact that I was using a passenger-side-drop front axle. If I had sourced a later-model driver-drop axle out of an '80s Jeep pickup, I could have used any easily sourced NP231 or NP242 T-case from a modern Wrangler, XJ, or ZJ. But that's not to say the Dodge axle couldn't work. To get a passenger-side-drop T-case without the need for expensive aftermarket adapters I bought a used Dodge NP208 online for $100. The Dodge NP208 has the same round six-bolt mounting pattern and 1x23 spline input as the Jeep AX15 and NV3550 transmission. Buyer beware, though. After paying to have it shipped from the Midwest, the unit arrived hammered and in need of a full rebuild. I brought it down to MIT in El Cajon to be cleaned, degreased, and fully rebuilt to be ready for service.

Because I was using a factory 4.0L bellhousing, that meant I couldn't use mechanical clutch linkage. Instead, I got a YJ clutch master cylinder from Advance Adapters along with the hydraulic lines. I determined the best position on the firewall where the actuating rod would make easy contact with the factory clutch pedal and used a hole saw to punch through. With the master cylinder bolted to the firewall, the actuating rod fell right where I wanted it to.

I whipped up a simple bracket that I welded to the clutch pedal and was able to attach the master cylinder actuating rod. The ratios all worked out fine, with the clutch releasing as the pedal was depressed.

I then assembled the bellhousing and hydraulic clutch parts I got from Advance Adapters to the NV3550 transmission including a factory replacement throwout fork, throwout bearing, and bronze input bushing for the engine crank.

A Jeep 4.0L is a bolt-in swap for an earlier 232 or 258 inline-six. I got a set of new polyurethane 232/258 motor mounts and a new NV3550 TJ transmission mount and started prepping the 4.0L to go in the Jeep FSJ chassis.

The 4.0L engine brackets are in the same location as on a 232/258. However, while the earlier Jeep engines use SAE-thread bolts, my '91 4.0L had one metric bolt on the rear engine bracket mounting hole. It kinda threw me for a loop until I figured out why the SAE bolt wouldn't grab properly, but once I scrounged a metric bolt out of my bin that fit, I had no problem getting the 232 engine bracket bolted to the 4.0L block.

I bolted a Centerforce flywheel and Centerforce II clutch to the back of the 4.0L engine and after installing an Edelbrock header, lowered the engine down into place. The motor mounts lined up with the frame perfectly.

With the engine in place it was short work to get the NV3550 and NP208 bolted in behind it. I was able to drill the factory crossmember to accept the factory TJ transmission mount and with the crossmember hanging off of the tranny mount, I positioned the drivetrain angle where I wanted it and then drilled four new holes through each side of the framerail to mount the crossmember. In all, it was one of the easier drivetrain swaps I've tackled.

The longest part of the drivetrain swap involved getting the new Hotwire Auto-prepped harness installed. Since the original wiring on this old Jeep was in questionable condition, I had Hotwire retain certain parts of the factory XJ harness outside of what was needed to actually fire the engine. Ultimately it worked out rather well, but in hindsight the whole project would've gone a lot faster if I had just had the company pare down the harness to the bare essentials necessary to get the engine to fire and run and left worrying about stuff like heater controls and wipers for a later day. Still, I got it all wired over about a week's time and then turned my attention to the finishing touches.

The original radiator was still in good shape, so I mounted a dual-fan Flex-A-Lite fan and swung it in the chassis before turning my attention to the fuel system. I used an external pump on this build, making a high-pressure line from the factory tank to the stock XJ line off the fuel rail. I plumbed the return line into the rubber fuel filler hose with a bulkhead fitting. It wasn't the most perfect job in the world, but it was more than adequate for this old truck. After installing a junkyard XJ throttle pedal assembly and finishing up some other odds and ends, the engine wouldn't fire. I was getting fuel and the engine cranked, but it just wouldn't spark. After some back-and-forth calls with the tech gurus at Hotwire Auto, they sheepishly asked me, "You did run a ground cable from the engine to the chassis, didn't you?" Duh—nope. After building a short ground wire and attaching it from the engine block to the framerail, the engine fired to life on the first crank and settled into a silky-smooth idle.

 

Power Steering, Interior, and Odds and Ends

When I first fired up the engine, the J2000 was still running the factory manual steering box. Since the XJ serpentine pulley obviously didn't allow me to pull the power steering belt, I looped the pressure line into the return on the power steering pump, effectively bypassing it from the system and allowing me to test drive the truck without a power box hooked up.

 

I ultimately grabbed a power steering box out of the junkyard. The common and easily sourced Saginaw 800 boxes share the same mounting bolt pattern on the framerail as the manual Saginaw boxes.

I honestly forget sitting here 12 years later exactly what kind of vehicle I yanked the steering box out of, but whatever it was I was able to disassemble the rag joint and bolt the half that came on the box to the half from the factory FSJ steering shaft, so no expensive U-joints or adapters were needed! The high-pressure power steering hose off the factory XJ pump also worked just fine, and after bending up some return lines, the truck had power steering for the first time in 40 years. I can't remember where the dropped pitman arm came from, but chances are if I didn't source it from Rubicon Express or Parts Mike I already had it laying around from my Ramcharger or some other project I had built.

Although the previous owner had done an interior refresh sometime probably in the early or mid-1990s, by the time I bought the Jeep the carpet was pretty hammered and the springs in the driver's side of the bench seat were completely broken and mostly missing. I got a pair of Smittybilt high-back bucket seats. In hindsight, I think a pair of low-back seats would've been a bit nicer fit, but the Smittybilt seats were comfortable and installed relatively easily by building some cross-runners atop the factory bench brackets.

I rounded out the interior refresh with a new carpet and door seals from BJ's Off Road and Smittybilt center console. The five-speed made freeway driving a pleasure, and despite being "only" a six-cylinder, the HO Cherokee 4.0L had plenty of gumption to haul and even tow a moderately heavy trailer.

 

Sources:

Advance Adapters
advanceadapters.com

BJ's Off-Road
bjsoffroad.com

Centerforce
centerforce.com

Dynatrac
dynatrac.com

Edelbrock
edelbrock.com

Flex-A-Lite
flex-a-lite.com

Hell Creek Suspensions
hellcreeksuspensions.com

Hotwire Auto
hotwireauto.com

MIT Drivetrain Specialists
mit4x4.com

Parts Mike
partsmike.com

Pro Comp Tires
procompusa.com

Rubicon Express
rubiconexpress.com

Smittybilt
smittybilt.com

Superlift
superlift.com