Last month we showed you how easy it was to upgrade the front suspension in a '56 F-100 by replacing the old straight axle with a Corvette IFS using a new crossmember from Flat Out Engineering. We were able to update both ends of the '56 chassis in about seven hours with the very capable help of the crew at Bobcos. Due to editorial space we were only able to show you the front conversion but, as promised, here's the rear upgrade.
It wasn't all that long ago that adding an independent rear suspension was considered really exotic and reserved for the high-end build-ups. But these days with the availability of well-engineered kits and the abundance of reasonably priced late-model Vette components there's no reason that anyone can't take advantage of the improved handling and "wow" factor that comes with this install.
Once you start to investigate the cost of rebuilding an old rearend and buying a suspension like a new four-bar set-up you start to see that the cost of the Vette unit isn't so bad. The Vette rears come with four-bars from the factory and depending on the kit you choose you can even use the stock leaf spring as well. Obviously, upgrades like coilovers or airbags are available depending on your budget.
Unlike the front suspension install, the rear can be bolted in. Mike Briggs at Bobcos did end up welding the pinion snubber brackets in place to save some time, but they could have been bolted in. The rear suspension install itself took under two hours and although we did it to a bare frame it could have been done on an assembled truck with a little more time.
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 Mike started the rear suspension...  Mike started the rear suspension upgrade by
removing all the stock suspension brackets and the crossmember that the shocks bolted to. A torch and an impact hammer were used to knock out the rivets. |
 Unlike the front kit, which...  Unlike the front kit, which requires welding, the rear kit can be bolted in. Everything needed to install the Vette rearend is there. |
 In most cases companies such...  In most cases companies such as J & D Corvette will supply the rearend with all the stock components intact. Here it is after Bobco's crew removed the original carrier and transverse spring. |
 The first thing that needs...  The first thing that needs to be done is to establish the rear axle centerline. The stock Ford centerline is 36 1/2-inches measured from the rear of the frame rail on 1/2-ton shortbed pickups. In most cases this works fine, but again it depends on tire size and personal taste. It's best to check your wheel and tire combo with the bed installed on the frame to get your own centerline. Whichever centerline you use be sure to locate all of the brackets from the axle centerline to insure they are all located properly. |
 Mike started with the rearend...  Mike started with the rearend wing mount bracket first. The center of this bracket is 4 1/2-inches behind the axle centerline (32 inches from the rear of the frame). Holding the bracket in place he scribed the bolt holes (the rear hole should be 29 7/8 inches from the rear of the frame). |
 Next he measured straightforward...  Next he measured straightforward along the framerail from the rear axle centerline 10 5/8 inches and marked a vertical line. He positioned the large forward control arm mounting bracket on the framerail so that the upper rear hole of the bracket was centered on this 10 5/8 inches measurement. Using the top and bottom edges of the framerail as a guide, Mike positioned the bracket in the center of the framerail and scribed the bolt holes. |
 After double checking all...  After double checking all the measurements he center-punched the scribed holes. |
 The holes were then drilled...  The holes were then drilled out to 7/16 inch. The brackets were bolted in place using the bolts supplied in the kit. |
 The Vette rearend was positioned...  The Vette rearend was positioned under the frame using a cart as support. Before it could be installed the square dampner bracket on the top ends of the aluminum wing must be removed (they are aluminum blocks with rubber isolators and aren't re-used). The rearend can now be bolted to the wing brackets. The large rubber bushings at the mounting ends of the wing have little knobs inside them for metric bolts. You must either use the stock Vette
metric bolts (which we did), or drill them out and use the bolts supplied with the kit. |
 The forward control arms (four-bars)...  The forward control arms (four-bars) were bolted up next. Again you need to use the stock Vette metric bolts or drill the end with the small eyed rubber bushings out to 1/2 inch to use the kit supplied bolts. |
 Flat Out Engineering offers...  Flat Out Engineering offers kits to use the stock Vette leaf spring and shocks or replace them with coilovers. This chassis will get the coilovers. Mike removed the two inside rear control arm bolts that mount the control arms to the outer hub retainer bolts and slipped the new brackets in place. The bolts were then re-installed along with the 5/8 inch bolts and nuts provided with this kit that bolt the lower shock mount bracket to the outer hub, where the stock Vette shocks mounted originally (the stock Vette lower shock mount studs must be removed to accomplish this). |
 In order to bolt the upper...  In order to bolt the upper shock mount to the framerail Mike had to measure forward from the rear axle centerline 3 1/8 inches and 6 3/8 inches. There were stock holes at these locations that needed to be drilled out to 3/8 inch. The upper coilover shock mount was bolted on the framerail using these holes and the bolts supplied with the kit. Using the bracket as a template, Mike center-punched the upper two bolt holes on the frame and then drilled them out to 3/8 inch and installed the two upper bolts. |
 The half-shafts were lifted...  The half-shafts were lifted slightly so Mike could install the upper coilover bolts. Make sure to install the coilovers with the adjusting knob
facing away from the framerail. |
 The folded double ear bracket...  The folded double ear bracket was bolted to the top of the rearend housing using the long stock Vette metric bolts (which mounted the aluminum torque arm from the rearend to the transmission on the stock Vette). The stock torque arm is not needed with this kit. |
 The boxing plateswere positioned...  The boxing plateswere positioned inside the framerails at the
approximate location of the upper coil mounts. Mike had to finesse the top of the rails a little to get the plates to fit
properly. The top and bottom rails of a frame are often not 90 degrees with the side rails as checked with a square, so this is not
uncommon. |
 The new crossmember was positioned...  The new crossmember was positioned between the boxing plates and bolted to the double ear bracket (pinion snubber bracket). The boxing plates were tapped into place so that the crossmember would be centered. |
 The pinion angle was then...  The pinion angle was then set at 2 degrees up (the transmission U-joint will be set at 2 degrees down). If you were to error here it would be better to error by setting it a little too high because you can shim under the folded double ear bracket on the rearend housing if necessary to bring the pinion angle back
down a little. |
 The crossmember was checked...  The crossmember was checked for proper
alignment using a tape measure and a level and then the holes were scribed and drilled into the boxing plate. The crossmember was bolted in place using the
supplied hardware. |
 Although they could have been...  Although they could have been bolted in place Mike decided that it would be easier to weld the boxing plates. |
 That's it. The chassis is...  That's it. The chassis is ready to roll. If you feel really ambitious you can detail the rearend by grinding off some of the brackets and tabs that are no longer used. Then, if you've really got some time, go ahead and polish it. It'll look so good it'll be a shame to hide it under a bed. |