If you looked closely at July's issue, you may have noticed that the Dumpster, my '65 Dodge M37 project truck, made it to Moab for the Easter Jeep Safari, so the cat's out of the bag: We got it done. However, through the magic of print media we'll be traveling back in time in this and future issues to continue showing some of the progress of the build. Of course, the Dumpster went to Moab without being 100 percent complete, so there is still plenty of things to button up. A while back we showed you the front suspension with link mounts and coilover shocks, and this month I'll head rearward to document a basic leaf spring install. It may seem basic, but in fact there are many items to consider when building even a "basic" suspension like the leaf pack under the Dodge. In addition, you'll see a little driveline tech about the Dumpster's new Driveline Tech driveshafts. The original rear springs on the M37 were spring-over, with tension shackles and a narrow leaf pack. This means the pack was above the axletube, and the shackle attached to the frame below the leaf spring at the rearward end of the springs. Though fine for military use, I was looking for something more flexible for off-road articulation.The original rear springs on the M37 were spring-over, with tension shackles and a narrow Many trucks (like this late-model Chevy) use long leaf springs with a thick overload spring along the bottom. (This truck also has a lift block and an add-a-leaf.) The long springs offer a more flexible suspension, while the overloads support heavy loads and helps stop axlewrap. Axlewrap is when the axle's pinion wants to twist upward, deforming the springs, rather than rotating the tires. In severe cases this can break springs and driveshafts.Many trucks (like this late-model Chevy) use long leaf springs with a thick overload sprin First, I cleared off all the old spring mounts and ground the frame clean to mount the new rear suspension. An angle grinder and an air chisel made short work of the old rivets and brackets on the frame.First, I cleared off all the old spring mounts and ground the frame clean to mount the new I decided to use a set of 63-inch Chevy springs on the back of the Dumpster, but I had to replace the hangers and shackles. Luckily I had an Offroad Design shackle flip kit, and I used the shackle flip mount up front as the spring hanger. To determine the location of the spring I centered the center pin within the wheelwell. As the spring compresses the axle moves rearward slightly because the spring flattens out and the shackle pivots.I decided to use a set of 63-inch Chevy springs on the back of the Dumpster, but I had to In the rear of the spring I worked with the guys from Pacific Fabrication to make a shackle hanger. I used the ORD shackle from the flip kit. Originally I set up the suspension with a compression shackle, where the leaf spring is below the frame mount, but the truck sat extremely tall. I mounted the shackle hanger at a distance from the spring hanger slightly less than the flattened length of the leaf springs.In the rear of the spring I worked with the guys from Pacific Fabrication to make a shackl I removed one leaf and the add-a-leaf springs from the spring pack. I felt that the Dumpster would be more of a trail rig than a hauling 3/4-ton, so I'm less concerned about the spring capacity. To do this I did need to replace the center pin bolts with shorter versions.I removed one leaf and the add-a-leaf springs from the spring pack. I felt that the Dumpst I also opted to flip the rear shackle to a tension shackle, where the spring is now above the shackle frame mount. The shackle hanger was designed to work in either direction, and this in effect lowered the truck and offered some protection to the shackle and leaf springs when dropping off obstacles.I also opted to flip the rear shackle to a tension shackle, where the spring is now above The rule is to keep the spring hanger level or lower than the bottom of the shackle no matter if it is a tension or compression shackle. This gives the leaf pack a slight forward rake and reduces oversteer when cornering. Oversteer is when the rear of the truck wants to drift toward the outside of the corner.The rule is to keep the spring hanger level or lower than the bottom of the shackle no mat By measuring the downtravel and then estimate the uptravel, I determined that only a 10-inch-travel rear shock would fit under the bed at full compression, and even then would only offer 3 inches of uptravel before the driveshaft hit a major crossmember in the frame. A new crossmember was added that also holds the upper shock mounts and a set of Icon Vehicle Dynamics 21/2-inch VS series shocks with piggyback reservoirs . These shocks are rebuildable and nitrogen-charged.By measuring the downtravel and then estimate the uptravel, I determined that only a 10-in To get the correct driveshaft angle, I used new spring perches from Off Road Unlimited. After setting the weight on the axle and measuring the possible driveshaft angle I determined that I would need a rear driveshaft with a constant velocity (CV) joint to prevent U-joint binding at full droop. Then I attached a long rod to the pinion and rotated it up just 1 or 2 degrees shy of the center of the output before tacking the spring perches in place.To get the correct driveshaft angle, I used new spring perches from Off Road Unlimited. Af I have used Driveline Tech driveshafts on many of my trail rigs because they can be made with 1/4-inch-wall thick tubing. This is overkill for most vehicles, but taking time to thoroughly balance the shafts means they spin vibration-free on the road and can hold up to abuse off road. Both my front and rear shafts use 1350 CV joints at the transfer case.I have used Driveline Tech driveshafts on many of my trail rigs because they can be made w The front driveshaft attaches to a special companion flange at the AAM front axle, but it still uses a 1350 U-joint. Driveline Tech can make a small-diameter shaft (these were around 21/2 inches) to allow for more clearance around oil pans, suspension links, and crossmembers.The front driveshaft attaches to a special companion flange at the AAM front axle, but it Both CV joints attach to a companion flanges on the transfer case and comprise two U-joints and a center pivoting ball to add more angle and reduce vibration.Both CV joints attach to a companion flanges on the transfer case and comprise two U-joint At the pinion end of the rear driveshaft, the 14-bolt axle uses a Blue Torch Fab pinion guard to protect the 1350 U-joint. The Driveline Tech driveshafts have a signature clearcoat on them, so there are no worries about rust (at least until some serious rock rash scrapes them clean).At the pinion end of the rear driveshaft, the 14-bolt axle uses a Blue Torch Fab pinion gu SOURCES Icon Vehicle Dynamics 1580 Commerce Street Corona CA 92880 951-272-4266 IconVehicleDynamics.com Pacific Fabrication 235 Tennant Ave. Unit 2 Morgan Hill CA 95037 408-250-1772 www.pacificfab.net Off Road Unlimited (Burbank) 300 N. Victory Boulevard Burbank CA 92504 818-848-2020 www.offroadunlimited.com Offroad Design 484 County Road 113 Carbondale CO 81623 970-945-7777 http://www.offroaddesign.com/ Blue Torch Fab 3211 11th Ave. North Birmingham AL 35234 N/A www.bluetorchfab.com Driveline Tech & Fabrication Inc. 761 Southeast 202nd Ave. Portland OR 97233-6105 503-465-0476 www.drivelinetech.com By Fred Williams Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!
