Ford 8.8 Axle Swap
As we intend on installing an ARB air locker now is a good time to drill and tap the 1/4" NPT hole in the differential case for the air line.
We also drilled and tapped a 7/16" x 20 tpi hole in the top of the axle for the TJs vent fitting which also is used to hold down the rear brake T-fitting. With the pinion angle set at about 17 degrees we drilled the vent hole in the top of the tube and spaced it about 2 3/4" from the flange on the differential.
Be sure to weld shut the stock Ford vent hole as it is in the wrong place for the TJ.
Mounting the brackets
Although there are many companies selling weld on brackets for axle conversions, only Mountain Off-Road Engineering (M.O.R.E) makes theirs specifically for the 8.8s huge tubes. Therefore no grinding is necessary to get them to fit.
As we are using the Rock Krawler axle truss due to our triangulated rear suspension we don't need the upper CA mounts or trackbar mounts.
M.O.R.E is happy to sell you only the brackets you need. We ordered the spring plates, lower CA mounts and swaybar mounts. Shock mounts will either be custom made or we will use the AEV shock shifter kit (formerly the Nth Degree Shock Shifter)
We start by measuring the pinion angle of our existing axle. With a lift of 4.5 to 5.5" the pinion angle should be between 15 and 19 degrees. With the 8.8 on jack stands we use a magnetic angle finder to set the pinion at 17 degrees.
We then position the spring pads so that they are at 0 degrees on the tube. The spring pads should be 39 1/2" from center to center. We measured 3 5/16" from the disk brake flange to the edge of the spring pads on each end.
The pads were tack welded in place, all measurements re-checked and then fully welded.
The Rock Krawler truss is placed on the axle tube and centered between the spring pads. Rock Krawler supplies a gauge that insures that you get the truss installed at the correct angle relative to the pinion angle.
With the STOCK diff cover in place using 2 bolts per side we place the gauges small end on the cover bolts and rotate the truss back to meet the gauge. Tack welds are then made so that we can check everything before final welding.
Because the truss eliminates the upper CA and trackbar mounts, set up is made much easier. The hefty 1/4" construction of the truss also strengthens the axle considerably.