Our transmission was purchased from JB Conversions with the low 6.34 1st gear. They are the only source I'm aware of to find the NV4500 with this early, very low ratio. We also purchased an Advance Adapters bellhousing with clutch release arm, dust cover, and pilot bearing through JB to mate the tranny to our Chevy 350 (part #712577). The tranny came assembled with a factory Dodge tailhousing which will mate directly to the Dana 300 transfer case without an adapter.

With the new transmission in the garage, we began removal of the T4 transmission that came in our Scrambler. Two hours later we had drop kicked it into a far off, dark corner of the shop. We then removed our 10.5" clutch, 153-tooth flywheel, and pilot bearing from the back of our engine. We could have reused our 10.5" clutch, but with enough room in our new bellhousing for an 11" clutch, we decided to upgrade while we were there. We ordered a Centerforce 168-tooth, 40LB steel flywheel (#700130) along with a pressure plate (#CF165552), clutch disc (#383735) and throwout bearing (#N1430). We removed the 1-1/8" 10-spline input gear from our T4 for use as a clutch-alignment tool while assembling our new clutch. With the clutch assembly torqued to the manufacturers specs, we bolted the Advance Adapters bellhousing to the back of our engine block. The Advance Adapters bellhousing has threaded bolt-holes to retain our original hydraulic clutch slave cylinder. The slave cylinder is relocated to the back side of the bellhousing requiring a large amount of grinding on the cast iron slave cylinder. The support rib of the slave cylinder had to be almost completely removed and a lot of grinding was required around the two holes on the mounting flange for clearance of the bellhousing to engine block bolts. With our old slave cylinder reshaped and mounted, our clutch assembly was finished.

Then the heavy work began, it was time to lift this 200LB monster of a transmission into place. Our rented transmission jack was begging for mercy, but the new transmission slid perfectly into place on the first try. With the new transmission bolted to the bellhousing, it was time to fabricate a tranny mount. You can order a transmission mount from Advance Adapters (#716021 for late CJ's), but it is designed for use with their own tailhousing, not for the factory Dodge tailhousing. The difference between the factory Dodge tailhousing and the Advance Adapters tailhousing is that the mounting pad is cast much lower into the tailhousing in the AA unit. A piece of 1.5" thick steel was picked up at a local machine shop for use as a spacer on our Dodge tailhousing enabling us to use the Advance Adapters mount. With the mount attached to the spacer and tailhousing, we lined up the crossmember to determine the location of the two holes to be drilled to attach the mount to the crossmember. Maybe it's just our luck, but the location of the holes lined up perfectly with a downward-angled portion of the crossmember. It would have been way too easy for the tranny mount bolts to fall right on a nice flat spot in the crossmember, I suppose - they just had to line up with a 1/2" section of the crossmember that wasn't flat. After a couple hours of head scratching and attempting to realign the crossmember to cure the problem, we gave up and made a trip to our local welding shop. We had the shop weld in a flat piece of steel to both sides of the crossmember to create a flat spot for the transmission mount. Holes were drilled in the new steel and the crossmember was installed. Problem solved...or so we thought. The NV4500 tranny is much taller than the T4. With the crossmember and tranny mount complete, the top cover of the NV4500 was in solid contact with the floorboard of the Jeep.

We could have lowered the transmission crossmember by using spacers between it and the framerail to allow more room between the transmission and body. That of course would decrease ground clearance and the breakover angle of our already long Scrambler. The solution was to call John White at JB Conversions one more time to order a 1" body lift. Two hours after receiving the parts, another problem was solved. As an added benefit, our 33" tires no longer rub the flares while articulating off road. The truth is we probably would have installed this body lift sooner or later anyway.

With the transmission firmly mounted in place, it was time to attach our Dana 300 case and hook up all the wiring and vent lines for our new transmission assembly. Since the NV4500 is much longer than our old T4, we used the old vent line for the transfer case on the NV4500, 6 feet of 3/8" fuel line was purchased to vent the transfer case to the upper firewall. The old 4wd indicator light wire was just long enough to reattach to the transfer case, but the transmission back up switch was another problem. The GM style reverse switch was not compatible with the existing plug on the Jeep wiring harness. Fortunately, GM dealers sell a wiring pigtail for the reverse switch (part #12085485). Just cut off your old harness end and splice in the GM unit. While we were at the GM dealer we encountered another nasty surprise: The NV4500 requires a special synthetic gear oil (GM part #12346190), and you'll need 5 quarts of it. The nasty part is that it's about $18 a quart. Since Dodge also uses the NV4500, they also sell the oil under part #4874459 for about the same price.

With the transmission and transfer case installed in their permanent position, it was time to take some measurements for the driveshafts. With measurements in hand, we called Tom Wood at Six States Distributors http://www.gowheels.com/sixstates/index.html and ordered a CV style driveshaft for the rear and a standard front shaft. Both shafts came with the U-joints already installed. Everything you've heard about Tom's driveshafts is true. They are works of art. They fit beautifully and the polished finish looks fantastic. We strongly recommend contacting him when it's time for new driveshafts in your 4x4. The rear CV shaft required replacing the output yoke of our Dana 300 transfer case and replacing it with the supplied yoke from Six States. This is a simple matter of removing the nut retaining the old yoke and sliding it off, then replacing it with the new one. We bolted up our shafts and carefully checked the rear pinion angle for proper alignment to the shaft. With a CV style shaft, the rear pinion yoke and driveshaft should have virtually no angle difference. In other words, the pinion should point directly at the output yoke of the transfer case. You may need to shim your axle to achieve the correct operating angle.

For most of you, this would be the end of the work required underneath the Jeep to complete the installation. There was one more part under our Jeep that was in dire need of work. We originally used Advance Adapters' fenderwell-exit headers on our Scrambler. The combination of headers and header mufflers directly underneath our feet turned out to be way too loud for our ears. To band-aid the problem, we ran pipe all the way to the rear exit with a pair of cheap-o turbo style mufflers underneath the rear tub. This made the noise level bearable, but left the exhaust pipe extremely vulnerable to rocks where it crossed underneath the frame just past the header. The section of pipe that crossed underneath the frame interfered with our new crossmember location prompting us to happily cut the entire exhaust out and set it out for trash day. Our solution was to purchase a new pair of exhaust manifolds for a Vortec TBI 350 truck from our GM dealer (driver-side part #2555002LH, passenger side #2554981RH). The fit is perfect and we can say goodbye forever to tightening header bolts and changing exhaust gaskets. As a word of warning, older Chevy truck manifolds will not fit as they are much wider than the manifolds we purchased. Older manifolds will place the exhaust outlet directly above the frame rails making pipe routing impossible. With our new manifolds installed, we got our hands on a pair of Flowmaster 2.5" mufflers and towed the Jeep to a muffler shop in our town well known for quality custom exhaust work. The shop carefully ran the 2.5" pipe and mufflers all the way out to the rear of the Jeep. There was very little space to run the pipe with the width of the NV4500 and transfer case taking up the majority of the room available between the framerails. To their credit, no part of the exhaust touches any suspension or drivetrain part under any condition, for a rattle free ride. The Flowmaster mufflers sound great - there's just enough noise under heavy throttle to let others know that you don't have a 258 under the hood, while at idle the exhaust just emits a nice low rumble. I have no doubt that the performance of this setup is much better than the previous header and 2" pipe combination, not to mention it can't get crushed on rocks.

With everything under the body squared away, it was time to clean up the interior. The shifter of the NV4500 is located in the top cover and not the tailhousing as is the case with our old T4. This meant that even though the NV4500 transmission was longer, the location of the shifter in the passenger compartment was actually several inches forward of the T4. Although the transmission shifter was moved forward, our transfer case was moved back more than two inches. Using the stock transfer case shifter would have required cutting into the body tub, not just the tranny cover, for installation. Since the stock transfer case shifter wasn't going to work, we purchased a dual transfer case shifter from Currie Enterprises since it is adjustable for different transmission lengths. We were able to relocate the new shifter forward enough to enter the floorboard at the stock location. I'd love to say the Currie shifter was an easy install, but it doesn't fit correctly due to the width of the NV4500 transmission. We had to shim the shifter mount as far as possible toward the passenger side, then bend the shifters to make it work right. The installation of this shifter would have been impossible without the JB Conversions body-lift installed. At this point the Currie shifter works, but while shifting we can feel the lever rubbing against the top cover of the transmission, so a little more bending and fine tuning is in order. At least we are enjoying the extra options this shifter provides over the stock unit. We purchased the twin stick boot with the Currie shifter and grabbed a Mr. Gasket shifter boot for our transmission at a local auto parts store. We used an Advance Adapters shifter handle (part #716050C) to have something to row through the NV4500 gears. This shifter is a very simple piece of straight steel rod with a threaded adapter at one end and a cheap plastic knob at the other. Not only did it cost an outrageous $65, but it hits my right leg every time I shift into second gear. If I had it to do all over again I'd make my own at cost of 90% less. From there we found a local sheet metal shop to obtain suitable material to fabricate a new transmission cover. A few hours later we had fabbed a new cover and the floorboard looked clean once again.

One more nasty little snag reared its ugly head when our McLeod mini-starter went out 2 weeks after completion of the transmission installation. The new GM manifolds are very close to the starter; combine that with the excessive manifold heat of a rich running carburetor and the McLeod had a melt-down. To make matters worse, the McLeod had a mere 15,000 miles of use. We decided not to waste $150 dollars on a replacement and headed off to the local parts store to try and find a stock replacement. After two hours of searching the store shelves and driving the clerk nuts, we still couldn't find a starter. Our larger 11" clutch and wider flywheel was creating a big problem: The only engine block mount starters they had were for the smaller 153-tooth flywheel. The larger 168-tooth flywheel starters that the store stocked had an offset mounting pattern not compatible with our engine block. Back to the mini-starter plan. We contacted MG Industries, manufacturers of high output alternators and "Mean Green" starters. The MG starter has a dual mounting pattern and is compatible with both sizes of GM flywheels. The Mean Green starter is a much more heavy duty unit than the McLeod, including a built in heat sink to prevent another meltdown. So far the starter has worked flawlessly; we even used it to load our Scrambler onto a trailer when we couldn't run the engine. The cranking power of this starter is tremendous.

As we mentioned earlier, this swap is expensive (see below) but worth it. Our Scrambler now sports a 70:1 crawl ratio with 4.10 gears in the axles. The low crawl ratio makes rock crawling a breeze since we no longer have to slip the clutch to keep from killing the engine. Another huge benefit of this transmission comes in at the opposite end of the spectrum. Our old T4 tranny didn't have an overdrive gear. At 75 mph the engine was at a noisy and gas consuming 3100 RPM's. Now at the same speed, our 350 is turning a lazy 2300 RPM. With the torque of our 350 this puts the engine at perfect speed for efficient highway cruising when needed. While we're talking about highway travel; for the first time in the 5 years we've owned this Jeep, the driveshafts don't cause any vibration. Even though our rear driveshaft is shorter than stock with the new transmission, the Six States CV driveshaft is perfectly smooth. For those of you who have driveshaft vibration in your Jeep, you know just how obnoxious this is. We are very pleased that vibration is a thing of the past in our Scrambler. If you need new 'shafts, call Tom.

Here's a breakdown of the major parts needed and their approximate costs for this swap:

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