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Jeep Guts Built For 40-inch TiresHeart & Soul From the November, 2011 issue of Jp By Pete Trasborg
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We worked with GenRight Off Road and managed to shoehorn 40-inch Goodyear MT/Rs under our Wrangler using stock springs and a 1-inch body lift (Part 1, July, ’08, Part 2 Sept. ’08). Then we got ourselves kicked out of our office building with our parking garage LT-1 V-8 swap (Part 1, Sept. ’09, Part 2, Nov. ’09). In the middle of all that, Trasborg moved, picked up a few more derelict Jeeps, and schemed for the perfect combination of transmission and T-case options to make this big-shoed Wrangler do it all. We are normally manual transmission guys. They have no issues with cooling, we can understand how the things work, and in dire situations you can almost always grab at least one gear and still get home. However, the Caprice cop car the 5.7L V-8 came out of had an automatic, so thanks to California smog laws, the Jeep had to have an automatic. The trick became how to make it live behind a V-8 in a Jeep with big tires. If that wasn’t enough, we wanted to be able to run in washing-machine-sized rocks, eel-snot-slick clay-based-mud, Abu-Dhabi-height sand dunes, and scenic trails—all with this same Jeep. That means we needed a low-low range, a regular-low range, and a normal 4-Hi setup. So we were looking at either a gear splitter in front of the T-case or a multi-speed transfer case. While the engine provides the power to the Jeep, the transmission and T-case are perhaps the most important components. Pick the wrong tranny, and you are slave to hard shifts or crappy gear ratios. Pick the wrong T-case and you will be cursing about how your low range is either too low or too high. Or, in the worst case, you will grenade the thing because it can’t handle the stress. Choose wisely, young Padawan. Level 10 Performance is well... Level 10 Performance is well known in the race world for its automatic transmissions. The company has been building automatic transmissions for 40 years. When you place the order, there is a simple tech form to fill out with information like vehicle weight, engine power, what you plan on using the vehicle for, and so forth. Level 10 picks the best springs, shift points, and stall of the torque converter for your application. After much research, we decided to send our 4L60E transmission all the way to the right coast and have the experts at Level 10 Performance do the rebuild and modifications. We were originally doubtful that anything could make that slushbox live with what it might be subjected to, but the company had no doubt that they could make it not only survive, but thrive with what we were going to throw at it. In fact, the guys at the company actually kind of laughed when we filled out the spec sheet with our vehicle’s power levels. Apparently, the transmission’s 1,200hp rating is just a little more abusive than what we will be throwing at it. Speaking of torque converters,... Speaking of torque converters, Level 10 builds its own. The angle and clearance between the vanes is important, as it affects the stall speed of the converter. Often the vanes in factory converters are only attached at one point to save time. Level 10 firmly attaches the vanes to keep them in place for the life of the converter. In lockup converters, the company also uses a better-than-stock friction material to prevent slippage no matter how heavy the drivetrain and tires are. For the transfer case, we went to Advance Adapters for one of its 4-Speed Atlas ’cases. The Atlas 4-Speed combines a planetary gearset in front of the tried-and-true gear-driven strength of the Atlas II, which will give a dizzying array of gearing options sure to handle whatever we throw this Jeep into. However, our timing sucked and we ended up placing the order at the same time the company decided the ’case needed to be stronger. We were on the very short list for the new-and-improved Atlas 4-Speed and put one of the fledgling few first builds into our Jeep for, ahem, “testing.” Once we finished clearing the cobwebs and the green stuff out of the wallet for some sweet bulletproof parts that we couldn’t build ourselves, we hit up Industrial Metal Supply for some steel so we could fabricate the transmission mount, skidplate, and shifter mounts. We also grabbed some junkyard parts to mate our previously manual-transmission-equipped Jeep with our new automatic and multi-speed splitter.  As for making the 4L60E live...  As for making the 4L60E live with a V-8 and heavy tires, there is really no one right answer. All the components of the transmission work together. By swapping in better solenoids, custom-drilling and machining the valvebody, and upgrading the friction material of the bands, the transmission will endure more power for longer. But that isn’t all—the clutch packs of each gear are bumped up and there is a better internal pump which helps the transmission hold gears and run cooler as well.  Since the engine and transmission...  Since the engine and transmission were out of a 2WD ’94, the tail end of the transmission had a four-bolt square pattern. Level 10 had the parts on hand to get us into a six-bolt pattern case at the same time they installed the Advance Adapters mainshaft and did the performance rebuild. Then we used an Advance Adapters ultra-short 1.25-inch adapter (PN 50-9305) that worked with whatever six-bolt, 23-spline-input T-case we went with. It provides for a VSS sensor leaving the Atlas tailhousing free for a speedometer. The kit comes with a transmission-mount foot that is threaded to accept a typical GM transmission mount (Advance Adapters PN 716654).  The new 4-Speed Atlas has...  The new 4-Speed Atlas has a higher input torque rating and is more reliable than the old unit. And while it has grown in length, it is still shorter than an NP231 and about the same length as an NP231 with a slip yoke eliminator. There are lots of options for gearing, but we aren’t fans of stupid-low gears. One of the reasons we went with this ’case was to allow us to wheel anywhere we wanted, so we went with the 1:1; 2:1; 2.72:1, and 5.44:1 gears. The 2.72:1 is the planetary with 2:1 inside the case, and both ranges engaged at the same time give us 5.44:1. We can do anything from huge rocks to bottomless mud to sand dunes.  We went to Parts Mike for...  We went to Parts Mike for this almost bolt-in parking brake kit designed to work with either two- or four-speed Atlas cases. We like this kind of parking brake because it simplifies things over running cables all the way out to the axle. The yoke-mounted disc won’t get gummed up with mud as with wheel-mounted parking brakes, and it offers added stopping thanks to the gears in the rear differential. The company has kits for other applications as well. While the caliper, caliper mount, and rotor all bolt on, the anti-rotation arm needs to be welded. This keeps the caliper from turning inadvertently. The arm needs to be set to length, tack-welded, and then removed for final welding.  We are big fans of the cardboard...  We are big fans of the cardboard template method of cutting parts out, especially when we only have an angle grinder on hand to cut with. Cardboard templates save money and time by speeding up the prototype process.  Once we got through the whole...  Once we got through the whole cardboard-prototype process, it was time to burn it home with our Lincoln Electric Power Mig 255C. The skidplate is made from 3⁄16-inch plate steel that we got from IMS. Not only are there several huge locations in the southwest, the company has good prices and great service. The company even loaded the truck for us.  There is nothing worse than...  There is nothing worse than balancing the tail of the drivetrain on a jack while trying to get a massive skidplate/transmission mount aligned and bolted up. So, we used some 1.5-inch, 0.120-wall HREW tubing that we got from Industrial Metal Supply along with some 1.5-inch, 0.120-wall square tube to build a transmission mount that is completely separate from the belly skidplate. We weren’t willing to cut the floor to clear the T-case, due to all the issues that show up inside the Jeep. So we ended up with the less-than-flat clocking you see here. We were shooting for a belly flat with the framerails, but every build has compromises somewhere. The Advance Adapters frame jack is very useful when building a mount like this.  Since the Jeep was a manual...  Since the Jeep was a manual and we didn’t want to go with the ultra-butch technique of welding the clutch to the brake pedal, we picked up a brake pedal from an automatic Wrangler from Max-Bilt. Max-Bilt makes cool heavy-duty consoles, but the company also has a staggering array of used take-off parts and ships anywhere in the country. We also added an automatic YJ floor shifter plate and an early XJ parking brake assembly from the company.  We mocked up a console using...  We mocked up a console using some ¾ by ¾-inch square tube from IMS. That cool gated automatic shifter is a Winters Sidewinder shifter from Wide Open Design. It features no brake interlock, no goofy button to hit to shift gears, and comes with a sealed cable shifter that is impervious to dirt and water. As shipped, it also includes a plastic mount to facilitate floor mounting. The other three sticks that look too long (because we have them mounted too high) are the three shifters for the 4-Speed Atlas. The two to the right of the automatic shifter are the front and rear axle controls and the one to the front of the shifter is the planetary control. We are waiting to route the cables until the exhaust and drivelines are in the Jeep. The last thing we need is shifter cables where the exhaust or driveshafts need to be. Once we route the cables and see how much effort is involved, we will decide if we are going to leave the shifters where they are and trim the sticks or move them closer to the floor.
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