Project Truck Long-Term Update - 15 Months of 47-Inch Tires on MatildaPosted in How To on May 1, 2011
It has been an experience.
After 15 months and a whole lot of modifications, our daily-driven fullsize Cherokee, Matilda, is a turnkey vehicle ready to go at the drop of a hat. This is probably more exciting for us to write than for you to read since we’ve had a backstage pass to everything that has happened with this project truck over the last number of months.
Parts have been added, parts have been broken, and the cost of ownership has increased slightly with this big dog. But it’s been a great trip, and we don’t ever regret teaming up with Jeeps R Us and delving into the task of building an off-road project with 47-inch tires that can still be driven to work every dayif necessary.
And we have in fact been driving it to work, to shows, and even to a wedding. If you live in the Southern California area, then you might have spotted this monstrosity cruising up and down the SoCal freewaysa sight to be seen, for sure. We would sometimes notice a gap of about 100 feet as other freeway commuters would give wide birth to the behemoth Cherokee. At first glance, we probably would, too!
Two years ago, we would have told you that driving at speed on 47-inch bias-ply tires was near impossible and should never be tried. Today, we’ve not only done it, but done it comfortably for hours at a time. The bias-ply Pit Bulls have really surprised us on the street. In fact, the only experience that has really shaken us in Matilda was prerunningthe short wheelbase and giant Pit Bulls made it so the Cherokee bounced back and forth from balancing on its front tires to balancing on its rear tires.
Aside from the scary prerunning experiences, this fullsize Cherokee on 47-inch tires has really turned out to be something we can put our seal of approval on. With the right combination of modifications, we were able to finish a vehicle that would do all that it is supposed to off-road, and still transport us safely down the roadways.
1 Admittedly, we did have some drivetrain problems to start. To begin with, we strapped 47-inch Pit Bull Growlers onto some Dick Cepek 20x12 wheels, and stuck them on a light-duty set of 3/4-ton axles under a fullsize ’77 Cherokee with a wildly-built 401ci V-8. One day, we just looked at the dirt the wrong way and three axleshafts snapped themselves in fear.
We knew that was coming (the timing was off, but we obviously knew), and we had already started building a 14-Bolt rear and Dana 60 front axle with 5.13 gears and ARB lockers in both.
Once the 1-ton axles were in place, we went out for some off-road testing, only to find a couple more driveline issues. The angle was too steep on the front driveshaft and we ended up breaking it. We also broke the rear one at a different time. In the rear’s defense, the snapping was only brought on after the lift blocks shattered and the axle was able to spin in the U-bolts.
2 Even after blowing a front driveshaft on one trip, we still decided to take a try at mudrunning. With the 47-inch Pit Bulls about halfway submerged in mud, we were doing pretty well until we hit a rut and couldn’t turn the truck to get out of the mud.
On a side note, this little stint very likely helped lead to the demise of transmission No. 1.
3 After Orange County Transmissions got the 727 transmission back in working order, we still had some severe front driveline angles to deal with and not quite enough gearing in low range. The easiest and absolutely best solution was adding a Klune-V underdrive unit. With the 4:1 Klune-V between the tranny and the Dana 300 transfer case, we were able to get 1:1, 2.6:1, 4:1, and 10.4:1 gear ranges between the transmission and axles. We also added an Advance Adapters 32-spline output to our Dana 300 T-case to ensure its strength. The control and ability to climb obstacles with 47-inch tires is now amazing.
With the Klune-V in between the transmission and transfer case, the driveshaft outputs were moved further back in the vehicle, necessitating a shorter rear ‘shaft and longer front ‘shaft. The longer front cleared up any and all driveshaft angle issues, and the shorter rear one was still in a safe zone.
J.E. Reel also recommended using long slip yokes on the driveshafts if we saw a lot of forward and rearward movement of the axles.
4 Right from the get go, Deaver multi-leaf-spring packs and Rancho Pro Series shocks were used on all four corners in this suspension and have really worked excellently on this Cherokee. The rear springs were actually take-offs from another vehicle (thus why we have lift blocks instead of a full-spring lift) but they flex well and support the rear weight.
The Deavers don’t give much more than a 6- or 7-inch lift to Matilda. But the lift, combined with a generous amount of fender trimming, allows for the 47-inch Pit Bulls to actually clear pretty well at all four corners. Due to the rear blocks, the big Cherokee did have some axlewrap (before adding some upper anti-wrap bars) that allowed a Pit Bull tire to get gouged beyond safe use.
5 Since the addition of the new front and rear ends, we’ve had zero problems with them. We started by finding a GM 14-Bolt rear axle and GM Dana 60 front bare housing.
The 14-Bolt is already very strong and was a slam dunk to finish off using an ARB locker and Superior 5.13 axle gears.
The front required a lot more attention. Dynatrac first cut and turned the axle to get the correct caster and pinion angles. The Dana 60 was packed with an ARB locker and 5.13 gears to match the rear, and Superior 35-spline American-made chromoly axleshafts were added as well. After that, we replaced the king pins on the housing and tightened on Reid Racing knuckles to the ends. An Offroad Design crossover steering kit was employed to join both orange knuckles together, and is controlled by a PSC-built steering box.
With 47-inch tires, any steering assistance is welcomed, and we were able to add a hydraulic-assist steering ram to our steering box since PSC had drilled and tapped ports when they rebuilt it.
6 Engine cooling was an issue we had been living with for a while. With more than 400 horsepower being used to push 47-inch tires down the road, the engine was definitely creating a good amount of heat—more than a factory radiator could handle.
We added a Champion Cooling three-row aluminum radiator in the factory hole. The radiators are built out of aircraft-grade aluminum and TIG-welded together. Each radiator is a specific-fit application.
7 How do you make enemies with a tire shop crew? Bring them a 47-inch tire that needs to be mounted on a 20-inch rim. Before we added some anti-wrap bars, the right rear Pit Bull tire got badly sucked up into the fender and the tread was basically split all the way down the middle of the tire.
We definitely wish we would have added the bars before learning our lesson the hard way. The price of a new 47-inch Pit Bull Growler is more than three times what we spent on materials to make anti-wrap bars.
8 Just to get the fullsize Cherokee running, Jeeps R Us had stuck an old CJ fuel tank behind the axle. Unfortunately, “temporary” become more permanent since it fit fine and held fuel without issue. But it was never mounted correctly, and it’s high visibility in the rear made it an eyesore. We managed to wrangle a CJ Crawler tank out of Tony’s hands at Gen Right. The 20-gallon aluminum fuel tank features a 3/16-inch steel skidplate that would hold the weight of our giant Cherokee if necessary. The beauty of the Gen Right CJ tank (besides its literal beauty and strength) is that it takes a YJ Wrangler fuel module.
9 The Gen Right Crawler tank fit up under the body and behind the rear axle with room to spare. There was a crossmember on top that we had to slightly modify, but the tank fit the same as the CJ tank did. Unfortunately for us, the fuel inlets on a CJ tank are on the passenger side, and we needed them on the driver’s side so we run the tank backwards and do not benefit from the angled lower rear corner of the tank. Fortunately for us, the Cherokee is so danged big that the tank will almost never touch any obstacle. Just in case, Jeeps R Us made sure to make their custom tank crossmembers strong enough to hold the weight of the Jeep, should the stout Crawler Tank ever need to act as a skid.
10 Our big Cherokee never really had a proper front bumper. It was something adapted from a small XJ Cherokee and made to fit. It actually looked okay and did hold a winch, but it wasn’t really strong enough to put a really hard pull on it. When we stuck a 20,000-pound Pierce winch on the front, we knew it was time to have something stronger built. Patriot Fabworks was only 20 miles from us in Corona, California, and we had heard about the custom bolt-on bumpers that they build. After explaining exactly what we were looking for, it only took them a few days to take measurements, laser-cut some frame horns, and TIG-weld something more permanent (but still removable) for us.
11 With the laser-cut framehorns bolted on, Patriot Fab cut and TIG-welded together each plate and tube, piece by piece. Each time Patriot builds a bumper the crew jigs it up so that the next customer with the same vehicle can purchase a bumper without having to hand over their vehicle for R&D. Since Patriot Fab had never built a fullsize Jeep bumper, the crew went to work building from scratch. It still only took them a few days between the time we dropped the Cherokee off and picked it back up.
12 Not only was our Patriot Fab bumper super clean when finished, it also had a dual-plane mount to hold our 20,000-pound Pierce winch. It was exactly what we were looking for.
13 On top of the Patriot bumper’s main hoop, we added two Baja Designs 8-inch Soltek race lights. The quality of the light is top notch, and stuck with halogen bulbs instead of HIDs since we knew we’d never (again) be getting over 50 mph in this thing in the dirt. We also added four halogen Fuego lights to the roof in front of the roof rack..
14 After adding some better lights and the 20,000-pound winch, it was obvious that we needed to upgrade from the tiny factory alternator that would barely charge the battery. The polished Powermaster alternator made more amps at idle and also produced more current at higher rpms.It almost doubled the amperage of our old, worn-out alternator and was just the correct ingredient to add to our electrical system.
15 Everywhere Matilda is driven, people gawk and stare. It’s one of those vehicles that you cannot not have an opinion about—you either love it or hate it. Either way, you have to admit that it looks absolutely killer with its new light grey paint job and tinted windows. We might just have to change the name to “Mean Matilda.”