Brothers Trucks 1963-1972 Drop Crossmember Installation

03/01/2016

Brothers Trucks 1963-1972 Drop Crossmember Installation

03/01/2016

The factory trailing arm crossmember in 1963-72 Chevy/GMC trucks is a stout piece that does its job well for stock applications. 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 Drop Trailing Arm Crossmember from Brothers 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 to exact specs before being powder coated black. The crossmember comes with all of the necessary hardware (grade 8, that is) to bolt right in the 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 our truck on the lift and the rear end supported by jackstands (essential for airbag applications), we began by removing the bolts that attach the trailing arms to the crossmember.

Next, the airbags were unbolted so we could move 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.

Our factory crossmember was hot riveted in place so you will need to grind the eight rivets that hold it in place. First, the rivet head was sliced in half with a cutoff wheel.

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.

Our particular crossmember was also welded in place (previous owner). The downside to all the solid welding done earlier is we had to remove it. There is one large bead on the top of the cossmember and two on the bottom of each side.

We 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, the crossmember was knocked loose from the frame with a small sledge. As you can see, the torch work caused minimal damage to the frame or old crossmember.

Once free, the crossmember was dropped out by sliding one side as far forward as possible.

We hated to do it, but we also had to grind the edges of the freshly powder coated Brothers crossmember to prep it for installation.

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 out, slide the new crossmember into its approximate place.

The trailing arms were then attached to the new crossmember with the provided hardware.

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 re-attached. 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 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.

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. The added benefits of exhaust cutouts are a plus.

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