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The blue suburban's ride was not what one might call "Cadillac," and with the 2.5" Rancho add-a-leaf over 4" blocks in the rear, it was no surprise. I already had Tuff Country's 6" front springs, so a set of 56" length lift springs for the rear should match the front perfectly. I paid a call to Stephen at Offroad Design who is always helpful, and we agreed that was the way to go. The UPS man was less than pleased lugging these 76 lb springs to the front door.
Chock the front wheels, pull off the rears, and put together a reliable way to hold the frame of the truck off the ground. I chose to use a combination of 2x6s, 2x4s, and 3.5 ton jackstands to support the receiver hitch.
Remove the springs to gain access to the shackle hangers. Spring steel is pretty heavy, so take your time, and go slow. The rear shackle hangers are attatched to the frame via rivets. That makes things a little more complicated when it comes to getting them off, but at Stephen's suggestion, we invested in an air hammer with rivet killer attatchment. Since we don't do this kind of work that often, we chose to go with the less expensive Craftsman unit.
Once we got the technique down, it took between thirty seconds and a minute to take off the head of a rivet, then driving them out was a fairly easy. It took a little while, but eventually we had all twelve off.
Once you have a bare frame, you can see that moving the brackets back to accomodate the longer springs is no big deal at all. The stock 52" springs have a center pin that is 26" from eye to center on both ends. The heavier duty 56" springs are 26" from the front eye to the center pin, and 30" from the rear eye to the pin. So all that has to be done to put in the longer springs is move back the rear hanger, and bolt them in. The holes are even pre-drilled on the frame.
We chose to go back with 7/16" grade 8 hardware. The holes in the frame are nearly that size, so we had to drill them out. Now, that's no big deal for the passenger side, but the driver side has the spare tire well, and that makes it difficult to get a conventional drill in there. We used a right angle drill with a short "jobber length" drill bit like these from NAPA. If things are really tight, then you can shell out the big bucks and use one of these stepped bits. The steps are just the right spacing for the frame thickness.
Now down the real challenge. How on earth do you get those bolts into the frame with the 40 gallon fuel tank installed? And if you're as lucky as us, it's full too! There isn't even room enough for an infant's hand to squeak by. Magnets. Go get a nice strong magnet with a flexible link, and you'll quickly see just how easy it is to get the bolts installed.
Now it's time to back with the spring hangers. We chose to use conventional nuts with lock washers, then followed with some nylocks for added piece of mind. All were torqued to 50 lb ft.
Hanging the springs is probably the easiest part of it all. Put your shackles on; taking note of which side they came off, put them back on the same side and orientation. The springs come with rubber bushings installed, but you can easily install greasable polyurethane pieces that Off-Road Design offers. We were short on time, and decided that the rubber bushings would survive just fine, but we did use one greasable poly bushing at the shackle pivot on the hanger since we had it on hand. Now is also a good time to inpect and replace your u-bolts and hardware. Since we were replacing blocks with full lift springs, we needed some u-bolts that were quite a bit shorter than those used with the blocks. We went to 4 Wheel Parts Wholesalers and got a set of Superlift u-bolts. Dimensions are 3 3/8" diameter, 5/8" bolt, and 8" in length. They came with new washers and nylocks. Locate the axle center pins in the spring perches, and start tightening the u-bolts.
After bolting on the wheels and double checking that everything is tight, it's time for a test drive. Like all projects, there is always a little fine tuning to be done. This came in the form of one of the the leaves trying to occupy the same space as part the hanger. With a little bit measuring and handy work with the sawzall, all was good.
Now, the truck actually rides better that it did with the flatter stock springs using an add-a-leaf and blocks. Surprisingly, there isn't that much arch in the new springs, so they should perform quite well off road. They were listed as 6" lift springs, but were more like 7" to start. It took a day or two, and they settled into their advertised height. The quality is top notch, and the conversion isn't a difficult one; it just takes a while.
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