How Jantz Engineering Drops Big Gears in Small Housings

August 29, 2013
Story By
Evan Griffey

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Extreme rock crawling has been built on a mountain of broken parts, broken hearts and broken bank accounts. The evolution of any motorsport leaves a smoldering trail of part failures in its wake and it’s a wicked scenario, a cascade effect where fortifying one soft spot only reveals the next weak link in the chain. On the trail it’s the drivetrain that absorbs the abuse. Over the years the tires have gotten bigger, the power to drive them has gotten bigger, and axles are being made of Kryptonite so the diff has become the big loser. Unfortunately the ring and pinion is the most expensive and difficult portion of the driveline to repair.

Every once in a while it’s not a big company with a sophisticated R&D department that comes up with a solution…it can be an enthusiast from the back-roads of America, a guy in a shop just trying to get his rig back in the game who doesn’t know any better that cracks the code…a guy like Carl Jantz of Jantz Engineering in Poulsbo, Washington. We are not saying his solution is first, best or the only way to go, we are just appreciating how the gears turned in Carl’s mind to conjure up his Jana Hybrid kits. The central theme of Jantz Engineering’s Dana-based (hence the Jana name) kits is interchangeability of parts. It all started after Carl and his trusty Willys Super Jeep chewed through six ring and pinions. While contemplating the big task of modifying deuce-and-a-half axles to work on his diminutive Willys, Carl had a moment of nirvana. He gazed longingly at the 70U light-duty gear set and contemplated all the fabrication it would take to graft the beefy 70 Series housing under his Willys. Then he eyeballed the girth of the 70 Series gears and compared it to the 60 Series housing and the difference was less than he expected. Could the gearset fit? A light bulb above his head flashed and the odyssey began. Carl’s trusty caliper revealed the difference between the diameter of the 70 spec ring gear and the Dana 60 housing was ¾ of an inch. Taking advantage of the liberal housing tolerances at work, Carl figured he could find 3/8 of an inch on each side.

Carl said he remembers thinking to himself, “If an engine guy can take a 400 crank, drop it in a 350 block and make a 383 stroker with the right custom bearing and grinder, why can’t I make a stroker rear end?” The other challenge was centering the pinion, The Jana kit includes an adapter pinion head bearing that positions the pinion depth deeper into the bore. While this moves the tail bearing, seal and yoke outward the Jana spacers, shims and adapter rings ensure proper alignment. The 70 Series pinion must also be shifted away from the pinion gear a scant 1/8 of an inch to allow the appropriate clearance for the larger pinion. The kit includes a narrowed adapter bearing.

The Jana Hybrid kit consists of the stepped bearings, conventional bearings, adapters, shims, seals and spacers. If a customer can provide the Dana gearsets, a grinder to clearance the housing and the ability to swap the gear parts they can do the conversion themselves – or, if needed, Carl can help source parts or Jantz Engineering can provide a finished product.

The payoff is a 33-percent increase in strength as Dana rates its 60 Series at 6,000 ft-lbs max torque output and its 70 Series at 8,000 ft-lbs. Max tire size is 44 inches, which usually means a serious, competition crawler or the like. The kit costs a very reasonable $340. The Jana 76 is stone-cold serious, designed for extreme machines like rock crawlers - but Carl has developed the Jana 54 Hybrid Kit ($305) that drops 50 Series gears in a Dana 44 housing for road-going, weekend warrior off-road rigs. Along with the beefier internals, this kit also allows the owner to choose from a number of final drive ratios while also upgrading to 35-spline axles. Jantz Engineering’s Jana K4 kit keeps it all in the Dana 44 family. It updates older 44s by allowing the installation of newer JK44 (almost 9-inch) gearsets. Gear ratios and axle splines can also be upgraded and Jantz reports a 44-percent increase in load capacity. The K4 kit starts at $340.

Generally speaking, a 40-inch tire like the Nitto Terra Grappler mounted on the white Jeep represents the limit of a Jana 54 or K4 set-up. “Parts just start flying after 40,”says Jantz, “I have broken more stuff on 42s pushing it than I care to remember.” From 40 to the 47-inch monster in the background, you’re looking at a Jana 76 kit. The un-mounted 35-inch Nitto represents the outer limits of most stock set-ups but Jantz warns that driveline longevity all depends on driving style and the horsepower of the rig in question. As mentioned in the lead-off paragraph, solving one problem tends to transfer the load to another component or system of components. The Jana kits can handle gobs of torque but they tend to challenge the stability of the housing. So Jantz Engineering has developed the Jana Girdle system to reduce housing deflection and take the flex out of the bearing caps.

The party starts with a custom 3/8-inch thick differential cover. The cover incorporates heavy duty load bolts and girdle system that keeps everything tight and lined up. Grade 8 studs are installed in the main bearing caps with Grade 8 nuts securing the cap in place. The stud girdle is positioned over the studs, with stanchions that go through the cover resting on the nuts. Nylock nuts secure the studs while counter-sunk cover bolts secure the assembly. Stout load bolts designed to apply pressure on the caps prevent deflection. The Jana Girdle (base price $300) is another extreme piece of engineering that not only saves bearing caps but in doing so also allows the ring and pinion to live longer.

Jantz Engineering also manufacturers a load bolt kit which further prevents ring gear deflection. It is similar to the set-up found in high-end drag race rear ends and commercial off-road equipment. Lastly, Carl Jantz continues pairing his useful engineering with practical genius to come up with clever inventions like his J-Flaters – which speed up the on-trail airing down of tires. Next up, join in on a trail ride with Carl and his Super Jeep! If you’ve used a Jantz Engeinnering product, leave a comment and let us know your experience!

How Jantz Engineering Drops Big Gears in Small Housings

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