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REWORKING MY FORD 8.8 REAR AXLE

I had three goals when starting this project: more clearance, wider stance and beefier tubes. Here is how it progressed.

Axle clearance before the shave.   The chunk cut from the axle bottom.

First, I measured the stock clearance, 5-7/8" from the fixture to the bottom of the F8.8. After marking the portion that I could trim, a reciprocating saw removed it with a bit of elbow grease.

 

I built a new 5/8" steel bottom plate to fill the hole after shaving the bottom. The little bump in the bottom is for ring gear clearance. Since I did not need the anti-lock brake sensor tone ring, or its pickup, I removed it and the bulky hardware in the top of the housing, and welded the hole closed.

 

As you can see, the amount of clearance gained at the lowest part is now 6-7/8". At the flat part of the plate it is 7-3/8". That is a gain of 1-1/2" over 90% of the bottom of the housing! The 3/4" thick reinforcing ring was cut out with a hi-pressure water-jet. I then transferred the holes from the F8.8 diff to the ring, drilled and chamfered the holes.

After bolting the ring to the housing with tapered socket head, stainless steel bolts, the next steep was to build a new cover.

The flat cover plate was fabricated from 5/16" thick cold-rolled flat stock. I shaped the gear cover portion from 1/4" flat pieces, then tack welded everything in place, frequently checking for gear clearance.

The 1/2" bolts on each side will press against the carrier bearing caps to reinforce them.

After fully welding the cover, I drilled and tapped another set of holes in the the reinforcing ring, then bolted the cover in place.

For extra strength the four bolt heads you see on each side of the ring attach it to the "webs" cast into the F8.8 housing.

 

Since the plan was to change the rear suspension from leaf springs to coils, I needed a flat area to weld the upper link brackets to.

I fabricated this unit that bolts to the reinforcing ring, and the nice flat area that Ford installed near the pinion nose.

I punched holes and "dimpled" them to add rigidity to the structure. Plus, it looks trick too!

Next, I cut the stock tubes off of the housing, leaving three inches sticking out. The stock tubes had been fully welded to the center section previously, making removal very difficult. If I had this project to do again, I would have removed them.

The stock tubes on the right are 3-1/4" O.D. x .188 wall, seamed tubing -- choice for replacement was 3" OD x .500 DOM. I had the diff end turned down to press into the stubs sticking out of the F8.8 shown above. The outer end received a custom flange to accept my Warn spindles.

The new tubes were built to add 3" to the overall width. After removing the seam in the stock tubes, I pressed the new tubes into the center section.

Above and below is the jig/fixture I built out of a chunk of "I"-beam. With center pucks and lineup bar installed. When I was sure everything was aligned, I welded the new tubes to the F8.8 tubes, inside and out. The housing was straightened with a 12 ton bottle jack when all welding was completed.

I decided to truss the top using adjustable rods, for future "tweaking" and to be able to preload the housing. Plus, the rod ends I’m using are the same size as my steering linkage, so it's a handy place to carry spare rod ends.

Here is the completed F8.8 under the CODE 4x4 Jeep. It received 4.56 Yukon brand gears, a Detroit Locker, Warn full float spindles and 31 spline alloy axle shafts. I ditched the stock Ford parking brakes but retained the Explorer disc brakes and calipers. The new width is 65" WMS to WMS.