Step By Step
The big problem with the spring-over conversion on our CJ-7 was the previous owner read in a magazine that soft springs were best, so he removed two leaves from each springpack. That made the Jeep scarier than The Blair Witch Project. Our solution was to replace all the springs with used but dead-stock CJ-7 units we nabbed for free from a buddy who'd installed a spring lift. New stock springs are available from Eaton Spring, if you prefer. With the full spring-packs, the Jeep became much more stable; it didn't handle as well as a spring-under Jeep, but it rode much better. To install the new used springs, we had to flip the center pins over to accommodate the spring-over conversion (the locating pin has to point down instead of up). We held the leaves together with a C-clamp to keep them from separating while the center pin was removed. We initially installed the new springs with the overloads installed, but later took them out.
While swapping the springs, we noted that the stock shackles (left) were pretty flimsy with rust, and the bushings were also causing some sway. We added new Daystar shackles and bushings for strength, stability, and an extra 1/2 inch of lift. We normally run soft rubber bushings for the trail, but the durable Daystar bushings made the Jeep more streetable. We also checked the condition of the often-cracked spring hangers and tightened all the mounting bolts.
People usually overlook the driveshaft when lifting their Jeeps. Surprisingly, the previous guy actually had the geometry correct (top) when he set the transfer case end and the diff end of the rear driveshaft at identical and opposing angles. He even had the 'shaft lengthened, but it was too long, so the slip-yoke bottomed out at full suspension compression. Also, we've found that long-travel, high-lift spring-over suspensions don't work too nicely without a CV joint in the rear 'shaft because the conventional joints quickly get stretched beyond their design limits. The bottom photo shows that we shimmed the rear axle to point the pinion directly at the rear T-case output so that a CV shaft from Tom Wood's could be installed. A Spicer (PN 2-4-4061X) CV-type rear output yoke for our fine-spline-output Dana 20 transfer case was also needed; early 10-spline Dana 20s take a different number.
Notice the shims we used between the spring and the spring pad to alter the rear pinion angle. By far the more preferable method would be to weld the spring pads to the axletube in the appropriate location, and we like the new design pads available from Con-Ferr.
Our CJ came with no shocks at all, though new mounts had been welded to the axle tubes. That's required with a spring-over because the shocks on '76-'81 CJs were originally on the lower spring plates. We wanted Rancho's RS 9000 shocks for their five-way adjustability and found the PN 9125s were the appropriate lengths (13.95 fully compressed, 22.82 fully extended). Also note that the rear brake hose has been converted to a much longer version to keep it from getting stretched out at full suspension droop.
It was important to deal with the loser short-style front upper shock mounts used on '76-'81 CJs; they're welded to the frame, and can be seen at the arrow. Later models had the tall mount shown on the right, and it's virtually mandatory to convert to the late style to install front shocks that won't limit travel on a spring-over suspension. Fortunately, 4 Wheeler Supply recently began reproducing the tall-style mounts, which we were able to install by using one of the motor-mount bolts that comes through the outside of the frame, then welding the rest of the mount. On the driver side, a fuel-return line needed to be moved to the inside of the frame. We used Rancho RS 9000 (PN 9014) shocks that measured 14.67 inches extended and 25.49 inches compressed.
Finally came tire selection. Since we didn't want to limit spring travel or add a 1-inch body lift at this point, we decided to stick with 33s for this mild street/trail Jeep, and we tried two setups to see what would happen. At the left is the new Goodyear Wrangler that measured a true 32 inches tall with a section width of 12 inches on a 15x8 Center Line wheel with 31/2-inch backspacing. The combo barely tucked the tires under the flareless fenders, but the steering stops had to be adjusted to prevent rubbing on both the leaf springs and the shocks. We also tried Mickey Thompson's new 33-inch Baja Claws on 15x10 Stockton Wheels bead locks with custom 21/4-inch backspacing. The Claws really measure 31 inches tall with a 13-inch section width. The shallow backspacing moved the tires outboard for extra turning clearance and stability, but they also make steering a bit tougher and really add a big load to the ball joints, wheel bearings, and axle U-joints. We think 15x10s with backspacing around 31/2 inches would probably be the best compromise for stance and steering clearance.
So you scored a cheap CJ-7, but ended up paying the price with a clapped-out suspension that's way south of roadworthy. That's what happened to us when we bought a $1,600 '77 model that's been the topic of our "How To Build a CJ-7" series in the past two issues. We love our 401 power, but with the T-18 in First, the suspension was so soft we could virtually lift the front tires off the ground at full throttle. Deceleration was twice as puckery, and cornering was...well, we just didn't corner.
Why? The owner before us had performed a slipshod spring-over axle conversion. CJs come from the factory with the leaf springs slung underneath the axles, and altering the suspension such that the stock springs are atop the axlehousings generally nets about a 4- to 5-inch lift so you can fit 33-inch tires, or 35s with some bumpstops and rear sheetmetal trimming. The good news is that a spring-over conversion is cheap because you use your stock springs. For the same reason, the ride is pretty soft, and because the leaf springs are virtually flat, axle articulation (spring flex) for trail use is impressive. The bad news is that a spring-over Jeep can be too soft for safe street use compared to a bolt-on spring-under suspension kit of the same lift height. Axlewrap, or wheelhop, is also a problem with spring-overs, and most people don't bother to correct the steering geometry or the driveshaft angles when they perform the swap.
Our '7 was a classic case of spring-flop gone wrong. The point of this story isn't to give you an all-encompassing look at CJ suspension but to show you how we tuned up our Jeep to make it street-safe and trail-worthy.
Lake Forest, IL 60045
Detroit, MI 48216
4 Wheeler Supply
Phoenix, AZ 85034