Since installing the Airlift airbag kit in Project Old School, the driveshaft comes dangerously close to hitting the top of the trailing arm crossmember when the truck is aired all the way down. For those of you that have never crawled underneath a '63-72 Chevy or occasional GMC, there is a large crossmember under the rear of the cab that the exceptionally long trailing arms on these models bolt to. On most models, the center support for the two-piece driveshaft bolts here. On some models and most hot-rodded trucks, the driveshaft simply passes through. The opening is plenty big for any and all suspension travel. Once you lower the truck, however, the driveshaft rides in the upper region of the opening, and if it ever began to make contact with the crossmember, it wouldn't take long for the crossmember to slice the driveshaft open like a can opener. Another byproduct of lowering is the loss of ground clearance. The stock trailing arm crossmember hangs down a few inches past the bottom of the framerails. And since this low point resides right in the center of the underside of the truck, it becomes a punching bag for driveways and speed bumps. A third issue arises with severely lowered trucks when it comes time to reroute the exhaust. The factory crossmember spans the area between the framerails, making it impossible for the exhaust to be routed along its natural path.
Early Classic Enterprises' new Extreme Drop Center Crossmember has solved all three of these clearance problems associated with 5 inches or more rear drops. Not only does the new unit give your chassis 2.5 additional inches of ground clearance, its raised center hoop design eliminates driveshaft interference on trucks with a slammed stance. This assembly also provides exhaust passages to allow you to run a 3-inch dual exhaust through the center of your chassis and out of harm's way. The Early Classic crossmember is fabricated from a 1/4-inch thick laser-cut and formed steel plate to be stronger and more functional than the factory unit, and it comes with a black powdercoated finish. The new design also retains the factory brake line, fuel line, and parking brake cable passages, and it is provided with all necessary grade-8 hardware.
If you are replacing the stock crossmember with the Early Classic unit, the big step involved is removing the eight stock rivets that hold it in place and bolting the new unit in with the supplied grade-8 hardware. Since Project Old School used to be a longbed, there was significantly more work involved since the old crossmember had been moved up in the frame and welded in place. This meant torching out the old crossmember, setting the new one into place, taking a series of measurements to determine that it was sitting perfectly square in the frame, and finally welding it into place. For this we called on Jim Iiams of IMZZ Industries in Brea, California. Jim is a master welder who has been scratch-building custom lifted and lowered suspensions for trucks for many years. IMZZ Industries can perform anything from a simple lowering job and wheel and tire packages to a one-off show-quality airbag suspension--so we knew we were in good hands. Follow along as Jim installs the Early Classic crossmember, and contact IMZZ Industries or Early Classic using the contact information in the source box.
The factory trailing arm crossmember...
The factory trailing arm crossmember in '63-72 Chevys is a stout piece that does its job well on a stock truck. On airbagged trucks or those that are lowered 5 inches or more, the driveshaft becomes dangerously close to rubbing on the top of the hoop. The stock crossmember also hangs down nearly 3 inches past the bottom of the frame. On a severely lowered truck, the exhaust routing also becomes an issue. This is where the driveshaft was currently riding with max air in the airbags.
The Extreme Drop Center Crossmember...
The Extreme Drop Center Crossmember from Early Classic Enterprises solves three different clearance issues, all the while looking much smoother than the original. The hoop is raised to give the driveshaft plenty of clearance, and in the process, leaves an additional 2.5 inches of ground clearance. There are also exhaust cutouts big enough for 3-inch pipes to make exhaust routing worlds easier.
The 1/4-inch steel is laser-cut...
The 1/4-inch steel is laser-cut to exact specs before being powdercoated black. The crossmember comes with all the necessary hardware (grade 8, that is) to bolt right in place of the rivets that hold the stock crossmember in place. You'll also notice that the openings for the brake and fuel lines were retained.
With Project Old School on...
With Project Old School on the IMZZ Industries lift and the rearend supported by jackstands, Jim began by removing the bolts that attach the trailing arms to the crossmember.
Next the airbags were unbolted...
Next the airbags were unbolted so we could lean the trailing arms
up and out of the way. The jackstands were lowered down until the shocks were maxed out--which gave us plenty of room to work. The driveshaft was unbolted and removed. Now is a great time to check your U-joints, pinion seal, or rear seal on your transmission.
Since Old School is actually...
Since Old School is actually a shortened longbed, the crossmember was moved up in the frame and welded in place. We'll be torching the crossmember out but the other 99 percent of you will be grinding the eight rivets that hold it in place. Early Classic was kind enough to send us a few shots of their recommendation for the process. First, the rivet head was sliced in half with a cutoff wheel.
Next, an air chisel was used...
Next, an air chisel was used to shear off the heads of the rivet. Finally, a pointed attachment was used to knock each rivet through the frame.
The downside to all the solid...
The downside to all the solid welding we did earlier was we had to remove it. There is one large bead on the top of the crossmember and two on the bottom of each side.
Jim made quick work with a...
Jim made quick work with a torch, but if you're not experienced with one, spending some time with the cutoff wheel might be a better idea.
With the torching complete,...
With the torching complete, the crossmember was knocked loose from the frame with a small sledge. As you can see, Jim performed the torch work with
minimal damage to the frame or old crossmember.
Once free, the crossmember...
Once free, the crossmember was dropped out by sliding one side as far forward as possible.
We hated to do it, but we...
We hated to do it, but we also had to grind the edges of the freshly powdercoated Early Classic crossmember to prep it for installation.
With the old crossmember out,...
With the old crossmember out, it was time to prep the frame for the new one. The entire area was cleaned up with a sanding disc.
Just like the old one came...
Just like the old one came out, Jim slid the new crossmember into its approximate place.
The trailing arms were then...
The trailing arms were then attached to the new crossmember with the provided hardware.
We then jacked the axle up...
We then jacked the axle up until the airbags could be bolted into place. We continued to jack-up the axle until it hit the frame, simulating the truck being completely aired out.
Finally, the driveshaft was...
Finally, the driveshaft was reattached. The new crossmember was now resting where it was most comfortable. More importantly, it needed to be checked and rechecked to ensure that it was sitting perfectly square in the frame.
A series of measurements were...
A series of measurements were taken. Points were measured from each edge of the crossmember to various like points on each side of the frame followed by cross
measurements to the same points. This measurement was to the rear bolt of the tranny crossmember. Luckily for us, each measurement was exact from the first one to the last. If this crossmember was off even an eighth of an inch, it would cause the truck to "dog leg" down the road. That means the rear of the truck would always be trying to change lanes and pass you up on the freeway.
After Jim determined the exact...
After Jim determined the exact areas to weld, he hit them one more time with the sanding disc to get them perfectly clean.
Their ability to run clean...
Their ability to run clean beads like this is why we chose IMZZ Industries for the job.
Next, the top edges were welded...
Next, the top edges were welded to the frame, and then Jim took it a step further and filled the eight mounting holes.
We're going to go out on a...
We're going to go out on a limb and say that this crossmember isn't going anywhere for a while.
After the welds had time to...
After the welds had time to cool, we touched-up the bare metal areas with some semi-gloss black. Now the truck was literally ready to roll.
This comparison gives a clear...
This comparison gives a clear view of the added clearance of the driveshaft, as well as the 2.5 inches of ground clearance you gain by installing the crossmember. We'll show you just how much easier it is to route the exhaust with Early Classic's clean new crossmember in a future issue.