1971 Chevy Suburban Superlift Suspension - Project SuperBurb Part IIPosted in Project Vehicles on September 1, 2002 Comment (0)
Last month we introduced our '71 Chevy Suburban and equipped it with some stout axles and lockers, along with a set of 4.88 gears. For this issue's installment of Project SuperBurb, we decided it was time to revamp the Sub's tired old suspension. Dreams of lots of lift and tires big enough to run over import cars filled our heads--but then we remembered that our Burb had to serve double-duty. Actually, it has to do more than double-duty, as the idea is to build one vehicle that could serve as an awesome tow rig, a comfortable daily driver and a capable trail rig.
For those reasons we decided to dial back the lift and tire size, since towing with 40-inch mudders didn't sound like a good idea. Plus we wanted a tire size that was somewhat easy to replace. Huge tires aren't easy to find in remote areas, which is where we tend to need them.
With all that in mind, we decided on a conservative 6-inch lift and 35-inch tires. For the 6-inch suspension system we turned to Superlift. Until very recently, all that was available from Superlift for the '67-'72 Chevy crowd was the company's heavy-duty front springs. But we felt that those would be a bit stiff for our purposes.
We were in luck, as the folks at Superlift informed us that the company's softer Superide springs were going to be available for the '67-'72 Chevys. Even better, we could get the first set. So after our new suspension arrived we busted out the tools, cleared out the driveway and went about slapping the lift on the Sub. What follows are the details and results of our toil.
So what's in store for the next installment? How does 340 hp, 450 lb-ft of torque and an overdrive sound?
The Before and After
We were surprised at the amount of flex that the Suburban had in stock condition. Most of it was due to the stock springs, which were completely worn out. Because of the softness of the springs, the Suburban was all over the road, and on the trail it would quickly blow through its meager suspension travel. In stock form our Suburban managed a 562 RTI score on a steep 30-degree ramp.
After the lift was installed, we hit the 30-degree ramp again. Though contact between the front tires and the fenders stopped our progress before the Burb could achieve full flex, it did manage an RTI of 603. We expect a slightly higher number after some fender trimming and after the springs break in.
Installing a suspension system isn't just about flex. We made large gains in approach and departure angles that will help the big Burb on the trail. The most impressive gain was clearance under the low-hanging transfer-case crossmember, and improvement that will help keep the Burb from high-centering. Check out the following before and after numbers.
|Approach Angle (Degrees)||33||52|
|Departure Angle (Degrees)||21||32|
|T-Case Crossmember Clearance (inches)||10||19 1/8|
|Front Differential Clearance (inches)||8 3/4||10 1/4|
|Rear Differential Clearance (inches)||6 3/4||8 3/8|
More Axle Beef
After last month's axle install we decided to do a little light wheeling. We quickly found that one of our hubs was busted. Upon disassembling the front Dana 44 we were horrified to discover puny axleshafts that looked like toothpicks, and tiny U-joints that looked like they came out of a Jeep.
A quick call to Warn solved our problems. First we ordered a set of Warn's premium manual-locking hubs for our Dana 44. But we knew we had to get rid of those puny axleshafts, so we also opted to get a set of Warn's 4340 chrome/nickel alloy shafts. They don't neck down like our stock ones did, and we can use the bigger and stronger 297X U-joint. Another nice feature is that they are machined to accept full-circle retaining clips, which do a much better job of retaining the U-joint.
Fire and Breaker Bars
Having an air compressor and an impact wrench sure is nice, but such accoutrements are not in the buildup budget right now. In place of air power, there are a few helpful techniques to remove stubborn nuts and bolts, and working on a 32-year-old vehicle gave us plenty of chances to use them. First, always have a big breaker bar in your tool chest to provide extra leverage. If that doesn't work, we take the handle off our jack and slip it over our breaker bar to make one giant extended breaker bar. When that doesn't work, and as a last resort, we break out the propane torch. We let the flame from the propane torch play on the offending nut for about two minutes. Then we spray it with Liquid Wrench or WD-40--neither seems to ignite. We then immediately attempt to remove the stubborn nut. So far this technique has worked for us--the heating and then instant cooling seems to free the nut every time. Once you've done this, though, toss the nut and/or bolt and buy new ones.
The Tires and Wheels
Due to the multi-purpose nature of SuperBurb, tire choice was very critical, since the tires we chose had to be able to tackle a wide variety of tasks. That is why we decided on a set of Pro Comp Xterrains in the 315/75R16 size. That's equivalent to a 35x12.50R16 in nonmetric lingo. They ride smoothly, are very quiet, and their aggressive tread does well in a variety of terrain. Another plus is their D load-range rating. We wrapped them around a set of 16x10 fully polished Xtreme Alloys from 4Wheel Parts Wholesalers.