Transmission and Transfer Case

I decided to use the combo of a SM420 transmission and a Dana 300 transfer case. The SM420 has a 7:1 first gear and is fairly short which helps the rear driveline length in a short wheelbase Jeep. It is also a beefy tranny and should hold up well to any abuse it may see. I went with the Dana 300 because it is also a fairly short t-case and is small to fit in the frame rails and without modifying the floor. I use a Novak adapter to mate the 2 together which is also the shortest adapter on the market at the time I bought it. I cleaned up both gear boxes and put in new gaskets and a fresh coat of paint. I also made my own twin sticks for the 300 similar to what Currie offers. To mount the tranny and t-case I built a combo skid and mount out of 1/4" steel plate. It bolts up through the frame using 3 bolts per side.

I used a Chevy cast iron bell housing from a 60's/early 70's truck. It was made for a larger input so I made an aluminum indexing ring on the CNC to position the SM420 input exactly in the center. For the clutch linkage I pieced together custom linkage. I used a Wilwood 3/4" master cylinder and a CNC push style slave cylinder. I used a stock Chevy cast iron fork from the same vintage as the bell housing. I fabricated a simple bracket that bolts to the engine block and bell housing to hold the slave cylinder. I purchased a braided stainless line from Afco racing to connect the two.

Drivelines

For the drivelines I decided to make my own out of square tube for 3 reasons: they are cheap to build, they are heavy duty and they are long-slip. On the front I used 1.5" and 2" square tubing due to space limitations and on the rear I used 2" and 2.5" square tube. Each piece is 1/4" wall. I cut off the yokes from front XJ driveshafts and then ground them to fit into a square hole. I did use a yoke from a Chevy driveshaft but later replaced it with another XJ yoke. To weld them since they are cast, I pre-heated the weld area, welded them and then allowed them to cool slowly. I also added grease zerks. They work well but I plan to buy or make a round rear driveshaft in the future. I would not recommend these for a street/highway driven vehicle, at least not for the rear shaft.

I use a Tom Woods Super Flex u-joint on the rear driveshaft at the T-case for increased driveline angle which allows for more axle droop. I also use a combination 1310 to 1350 u-joint on the other side of the rear driveshaft to mate the driveline to the 14 Bolt axle.