If there has been one underlying theme to our '68 J2000 project it's been moderation. In Part II, we bolted on some simple Hell Creek Suspension 4-inch lift springs and 33-inch Pro Comp AT tires. In Part III, we rebuilt of a pair of Dana 44 axles with 4.56 gears and Eaton Truetrac differentials. Last time, we covered the axle installation. All in all, we've tried to use non-exotic and junkyard parts where applicable. So when it came time to gather parts to replace the tired 232 engine and insufficient T-14 tranny, we shelved thoughts of high-horsepower V-8s and crazy overdrive automatics.
With fuel prices climbing higher and faster than an SR-71 Blackbird, a fuel-efficient 4.0L Jeep engine seemed a sane choice. Plus it would bolt right to the 232's engine brackets. The 4.0L's 190 hp and 225 lb-ft would move our J-truck well, and when coupled with an NV3550 five-speed, would probably knock down decent mileage numbers. We're hoping for 18 mpg with our 33s and 4.56 gears.
We began searching for a wrecked Wrangler or Cherokee from which we could pirate the whole drivetrain, but after a few months of failure we gave up and put in a phone call to Scotty's Jeep, Truck & 4x4 in Fontana, California. Scotty's has a massive Jeep wrecking yard and keeps a huge inventory of all sorts of Jeep parts on hand and ready for shipping. The company had a good 4.0L taken out of a '92 XJ with a five-speed transmission. We got the engine, accessories, wiring harness, and computer and had the gang at Scotty's load it into the back of our J2000.
As for transmissions, we stumbled across several AX-15s for sale, but we never would have trusted the relatively light-duty transmission with some of the heavy hauling and moderate towing we expect this truck to do. Instead of going the junkyard transmission route, we placed a call to Advance Adapters for one of the company's remanufactured NV3550 transmissions and everything we'd need to mate it to our 4.0L. That included a bellhousing, slave cylinder, release bearing and arm, and slave cylinder-to-clutch master cylinder hose. But you'll see more on that in a future issue.
As for the T-case, we originally obtained a brand-new NV231 from Advance Adapters since we had planned on using a late-model J-truck front axle with a driver-side drop. But when we wound up using a passenger-side drop Dodge front axle, we returned the NV231 and began looking for an early '80s Dodge NP208 T-case. The Dodge NP208 bolts right to an NV3550 tranny and comes factory with a fixed yoke on the rear so there's no need to buy expensive adapters or slip-yoke conversion kits. We bought a used NP208 online and took it to M.I.T. Drivetrain Specialists in El Cajon, California, for a full rebuild to ensure years of trouble-free service.
Read on to meet our new drivetrain. And tune in next time to see our engine get prepped for installation into our vintage pickup.
We're currently on Plan D or Plan E as to how we're going to get the 4.0L to run in our truck. We're still weighing our options, but in case we decide to use the factory harness and computer, we carefully labeled each connector as it was removed from the engine. Scotty's even included the XJ's underhood fuse box and bulkhead connectors, so our options are wide-ranging. | 
Aside from the ubiquitous cracked exhaust manifold, the '92 XJ 4.0L from Scotty's was in superb condition. Scotty's test runs each engine it sells to check oil pressure and listen for noise. Then a compression check is performed and the oil is checked for signs of coolant. Ours was in great mechanical condition. | 
We pulled the intake to get the cracked exhaust manifold off. It will be replaced with a header in the next installment. Our intake, throttle body, and valves were in great shape, with little-to-no carbon buildup. |
Advance Adapters carries just about any component you could want for your Jeep's drivetrain-plus a couple you never thought of. Our NV3550 arrived completely refurbished. Ours is out of a Liberty, as evidenced by the bend in the shifter. We'll address that when we do the install. The NV3550 is fully up to moderate towing duties and dealing with the weight of our big J-truck, even with 1,000 pounds of cargo in the bed. | 
Our 4.0L didn't come with a bellhousing, so we ordered a new one from Advance Adapters. We also ordered the throwout bearing and arm, slave cylinder and hoses, and a few other key components we'll need to sling this transmission in our J2000. We'll cover the full drivetrain swap in an upcoming issue. | 
Used in 1/2- and 3/4-ton Dodge trucks from '80-'87, the NP208 will prove a durable and quiet-running T-case for our J-truck. We found this '81 Dodge NP208 for sale on ramchargercentral.com and bought it for $100 shipped to our door. |
To be on the safe side, we put the money we saved not buying adapters and slip-yoke conversion kits into having M.I.T. rebuild the NP208. Technician Andy Thomas fully disassembled our T-case and ran the parts through the company's industrial degreaser machine before performing the rebuild. | 
M.I.T. installs top-quality DT Components rebuild kits. And as you can see, our T-case needed one. The NP208 is not as rebuilder-friendly as the later 231 and 241 T-cases, so it's a good idea to have a pro spin the wrenches for you if you haven't already rebuilt a couple of these old-school beasts. | 
Thomas stripped our T-case down to the core to make sure every part was as good as new. Every bearing, bushing, and synchro needed to be replaced in our worn case. |
Even with an expoloded diagram, the NP208 can be a tricky bitch to get together. Unlike later NV231 and NV241 cases, there are a lot of levers, pins, and splines to align when installing the planetary, main shaft, and shift fork into the case. Thomas has done it hundreds of times, so we happily played dumb monkey and just shot photos. | 
Each shaft spline and gear tooth is checked for cracks, chips, and wear before the synchros, sprockets, and planetaries are installed. M.I.T. stocks a huge supply of somewhat obscure new and used parts in case replacements are necessary. | 
The task of aligning the shift fork, shift lever, main shaft, and planetary while not dropping synchros or gears into the case is a dicey operation. You've got to get it right or the T-case will bind, break, or just plain not work right. |
The installation of a new chain from DT Components signals the last involved step in the rebuild. With the new components, our T-case will last the rest of this truck's conceivable life. | 
Like the Jeep NP208, most Jeep NV231, and all NV241 T-cases, the Dodge NP208 has a 1x23 input shaft that accepts most modern Jeep transmissions. The round six-bolt patterns match, requiring no adapter. | 
Thomas laid a thin bead of black RTV before installing the rear case half. The oil pump is housed inside the output shaft tailhousing, so at least one step in the rebuild process is easier than with the more modern NV cases. |
Dodge 4x4 trucks of the '80s used Saginaw-type CVs and U-joints instead of the more common Spicer types. It's not a big deal since replacement Spicer yokes and flanges are available for the NP208. Since our J2000 truck will need new driveshafts anyway, we're going to leave the Saginaw flange and yoke on our case and have some Dodge-type shafts built for our truck. | 
One item we had to consider is the stickout length of the NP208. Thankfully the T-case bolted right to the NV3550 without the tranny splines bottoming inside the T-case input shaft. Likewise, the input shaft of the T-case didn't make contact with the bearing retainer and seal of the NV3550. Had the units bottomed out we would have had to use a 1-inch spacer between the tranny and T-case. | |