With the rear frame of the...
With the rear frame of the car planted firmly on jack stands, lower therearend so the stands support the weight of the car. The jack remainsunder the rear to help in the axle removal.
Last month we discussed the rearend buildup of Project Valiant Effort, wherein we fitted our boneyard 8-3/4 rear (a replacement for the original 7-1/4 rear) with taller gears and an automatic locker. With either rearend configuration the 360, which will ultimately sit up front, will have no problems leaving rubber signatures at the stoplight. The 7-1/4, however, would only be able to handle that kind of activity for a short time. With the 8-3/4, the durability issues are corrected (hopefully), and since we are planning ample quarter-mile blasts in the Valiant, we wanted to solve the problem of body flex as well.
Several aftermarket companies offer weld-in subframe connectors to minimize body flex. The problem is that most of these kits require cutting the floorpans, with the connector protruding into the passenger compartment. This presents a difficulty for rear seat passengers, and makes carpet installation a problem.
If you have access to a mig welder, a less-intrusive subframe job can be accomplished in your driveway. If you're uncertain of your welding skills, you may want to have an experienced welder handle the subframe installation for you.
Unhook the emergency brake...
Unhook the emergency brake cables and the rubber brake line above therearend. Remove the U-bolts and drop the axle assembly.
It's easy to see why the 8-3/4...
It's easy to see why the 8-3/4 will hold up better than the original 7-1/4 unit under heavy-hitting torque applications.
Before you bolt an 8-3/4 in...
Before you bolt an 8-3/4 in place of a smaller axle assembly, keep in mind that the axle tubes are bigger and, as this picture shows, the spring plates and U-bolts must be similarly upgraded. Fortunately, our 8-3/4 came with plates and good U-bolts.
With the new rear supported...
With the new rear supported by the jack, slide it into place and bolt itin. Don't forget to reconnect the brake line and emergency brake cables.
We obtained a loaner set of...
We obtained a loaner set of wheels and tires from a friend. Being255-70-15s, they're a bit tight for our purposes, but adequate formoving the beast around the shop.
Since we now have a rearend...
Since we now have a rearend that can take whatever we throw at it, we'llneed to address body flex. Unibody cars are notorious for twisting whenheavy horsepower and serious traction upgrades are applied. We went tothe local welding shop and bought two pieces of 1/8-inch thick 2x2square tubing that were 44 inches long. The cost was a mere $12.50.
Fit the square tubing to the...
Fit the square tubing to the front frame area, hold it against the rearframerail, and mark where you need to cut for the connector to fitinside the rail. Here you can see the portion that will be trimmed off.
After you cut the framerail,...
After you cut the framerail, but before you weld in the connector, makesure the connector is as far up into the framerail as possible. Itshould rest against the floor at the rear frame. Also, do not cut theopening too large; the connector should fit snugly into the framerail.
The front of the connector...
The front of the connector should also be tight against the crossmemberbefore any welding begins.
With the connector properly...
With the connector properly positioned, it's time to weld. Remember thatthese welds will receive significant stress under aggressive drivingconditions, so your welds must be solid. Completely weld around theframe where the connector is inserted into the rear framerail, as wellas around the front of the connector. For added insurance, some piecesof plate steel can be welded at the front where the connector meets thefront frame.
When you have completely welded...
When you have completely welded in your connectors, give them a goodcoat of primer and paint. Now, bolt on those slicks and hit the track.