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Narrowing the Ford 8.8 Differential

Original Ford 8.8

I realize that my use of the Ford 8.8 differential for this project may spark some debate – it’s too heavy, too this, too that. Perhaps true but, be that as it may, I have what I consider to be some very good reasons why it’s an excellent option, not the least of which is that I acquired my example for a paltry $250 (including the freight charge to get it here from Ohio). I’d also add that there are a multitude of carrier and axle options including the original Trac-Loc, Detroit Locker, Moser, and the like to choose from when building it out that make it a very flexible starting place. Now, on with the show.

Getting It Ready

Brackets removed

First step was to remove all of the original brackets, the axles, and drum brake backing plates. The axles are easy to remove on an 8.8. Off with the cover, drain out the fluid, pull the pin holding the spider gears in, push the axles towards the center, push the c-clips off the ends and then slide the axles out. The c-lips aren’t used for the new axles which are “eliminator” types that use a pressed on bearing and retainer. The backing plates come off by removing four bolts on each side. The brackets, which seemed like the easiest thing to do, turned out to be more of a challenge as I don’t have a cutting torch or plasma cutter (but I may consider getting one if I keep dong this sort of thing) and had to resort to either my Sawzall or a cut off wheel. Neither was the ideal tool for the job

Suspension brackets removed

but the cut-off wheel got the nod for its maneuverability. It took a series of cuts (and a large hammer) around the axle housing to do the deed but once the old brackets were gone, I cleaned up what remained of the welds and was ready to measure for where to narrow each axle housing. Because they wouldn’t be used in this set-up, I also removed the suspension points cast into the housing for Ford’s four-link set up using the Sawzall with a “Torch” blade and an angle grinder to tidy things up. Smoooooth.

Measuring…Over and Over Again
The rear end, as it came, was a bit over 63″ from axle flange to axle flange and my new width needed to be 51.5″ to accommodate the wide tires and new bodywork. Measuring for correct

Measuring tire cross section

Measuring fender to fender

width is actually pretty easy but I managed to second and third (even fourth and fifth) guess myself so much that I began to feel like Moser technical support was a self help line. At the least I’m confident I gave them something to laugh about for a while. To say they were indulgent would be understatement. Great folks to work with.

Starting with the inside the fenders distance, the measuring goes something like this. Fender lip-to fender lip – 2x tire clearance (3/4″ in this case, 1 1/2″ for both) – 2x the rim offset (4 5/8″ x2) = axle flange-to-axle flange. Subtract another 2 1/2″ + 1/4″ for the rotor hat thickness x 2 and that gives you the axle flange-to-axle flange distance. Lastly you subtract 2 1/2″ more from each side (5″) for the length of the new housing ends and then divide by 2 to get the length of each axle tube from the center of the pinion gear. Confused yet? I was. But, a call to Moser confirmed that my math was correct so I was good to go on cutting the axle tubes.

No going back now

Using a Sawzall to cut the axle tubes probably isn’t the ideal choice – I think a cut-off saw would have been the best tool in terms of keeping the ends absolutely square and limiting any hand work, but the Torch blade and some carefully placed tape made easy work of it and proved to be remarkably accurate. I cleaned and finished squaring up the cuts with a flat file.

Welding On the New Axle Housings
This is where I needed to get creative. As it turns out, virtually all aftermarket housing ends are built for the more standard 3″ outside diameter axle tubes rather than the 2 7/8″ tubes used on the 8.8. Those crazy Ford guys. What were they thinking? That meant the inside diameters of the axle tubes and housing were different, making centering them the biggest challenge. I

Moser ends for 9″ bearing, nice

solved my dilemma by taking a 2 7/8″ to 2 1/4″ exhaust adapter, sawing the ends of so it was about and inch long then slitting it down the middle (more about that in a few sentences). What resulted was a piece that pressed firmly into the housing end and also into the tubes, nicely centering the ends so they could be tack welded. Once complete, I simply slid a screw driver between the housing and my centering cone, then bent it down and finished removing it with a pair of needle nose pliers (hence why I slit the tubes).

Leveling the assembly before welding

Before welding, I leveled the assembly using my magnetic angle gauge then tacked the ends on the top and bottom making sure they were perfectly perpendicular to the tubes. Once done, I rotated the assembly 90 degrees and repeated the tacks, making sure the ends were perpendicular in both planes. “Easy peasy”, as the Brits would say. After that, it was just a matter or stitching between the tacks being careful not to heat the tubes too much and warp them.

Finishing Up
With all of the brackets gone and the new axle housings in place, I replaced the locking pin for the Traction-Loc, cleaned up the cover, and bolted it back on. After a solvent bath to remove any road grit and filth, I used a rotary wire brush to remove any leftover rust and scale, then laid three nice coats of epoxy-based black chassis paint. This tough is as tough as nails and, even though it comes out of a rattle can, puts down an impressive finish.

The finished product

Allstar Performance spring perches

Panhard bar bracket

Next came measuring for and installing the spring perches and Panhard bar bracket. I went with bolt-on components for this so I could have some adjust-ability with the pinion angle as well as the Panhard bar. Same deal as the axle housing ends though, everything is made for 3″ axle tubes so some creativity had to be employed to get things to fit. In this case, it meant trimming an 1/8′ off each of the parts halves, then bending the ends in slightly to make everything fit nice and snug. Not a big deal but one more thing to do. I also thought about shimming them but felt that cutting things down would produce a firmer fit. Hope I’m right, because spinning the axle under load would be a HUGE bummer.

Perch angle set to zero degrees

Pinion angle set to 3 degrees

Once the perch modifications were complete, time came to install them. Finding the correct distance, left to right, is pretty simple—just measure from center to center on the leaf springs, add/subtract one-half the width of the new perch, then mark the location on the axle housing. Go it? Seriously, it seems very simple (and it is) but it still took me twice to get it right. Next thing is to set the pinion angle so the perches can be installed at a level. For my application I needed about 3 degrees of angle (as seen in the pic) to end up with the correct alignment for the drive shaft. After that, it was just a matter of installing the perches and setting the perch angle to zero degrees then tightening them up. The pinch bolt on top helps ensure the perch stays put. As said before, spinning this assembly would not be good. The advantage of the bolt-on perches is the ability to adjust the pinion angle once the everything is in the car, on the the off chance I have my original settings wrong. Once I know for sure that everything is correct, I may have the perches tack welded in place as some added insurance.

New Axles, Bearings, and Retainers
It doesn’t get much easier than this. Order the new axles to length from Moser which come with the bearings and studs already installed. Slide them into the tubes and bolt down the retainers. Done. That’s it. Next will come the installation of the disc brake package and the e-brake cables.

Epilogue

After heat and quench

Well, if you’ve been following my thread over on the MG Experience forum, you know that all was not well with the new set up—the new flanges were welded on out of square in both vertical and horizontal planes. Initially I thought things were fine but Jim Stabe convinced me to try a more accurate measuring technique. I was horrified at the result—toe out and negative camber (and significant amounts) built in due to the poor assembly work. Disappointed doesn’t really cover how I felt. Thankfully, not only did Jim provide me with an accurate way to measure things, he also gave me a solution called “heat and quench” that didn’t involve cutting the ends off and starting over.

The other side

I know you can heat and shrink metal but had never thought of applying the idea to something like an axle. Let me tell, you it was really something to see the flanges move when the quench was applied right after heating the area to cherry red. It took several tries to get things into alignment but eventually I was able to get things within reasonable tolerances.

Initially I was using a magnetic angle gauge to determine trueness, believing it would be accurate enough for this application. Not so. On my second attempt, I bolted two 6′ pieces of angle iron to the housing flanges and measured the run out at 12″ and 24″ from center on both axis. What an eye opener! That fraction of degree using the angle gauge turned into 3/8″ at the 24″ mark on the horizontal plane and a bit more than that in the vertical plane. Yikes!

It took me a couple of hours to get things right. There’s a lot of technique to this method but it was fun to try and I’m happy with the results. I think this is also a viable way to intentionally impart both camber and toe-in to a live axle rear end. It might take a few trials and errors to get it accurate but it’s an easy method to use and I was able to get the hang of it after just a few attempts. You’re mileage may vary with your patience. I’m sure I now know just enough about how to do this to make myself truly dangerous but it’s a nifty skill to have. I’m sure it will come in handy again.

The Saga Continues
Cleared all of the metal filings and crap from the heat and quench cycles out of the axles tubes and installed the new axle

Left side installed

Bearing retainer installed

seals in the Moser housings. These aren’t your garden variety 8.8 seals but one’s from Moser to fit the bigger than stock diameter of the new axles. I lubed the new seals as well as the o-ring on the Ford 9″ bearing already pressed on to the axle shafts and slid it in to the housing. I’m not sure what I was expecting (a bit of trepidation maybe given the whole alignment adventure) but the axles went right in with a little resistance from the o-ring, something I was told by Moser to expect. A tap from the rubber mallet (and I do mean tap) and the bearing slid home. The only confusing part is the fit of the reatiner plate which, as you can see in the pictures, sits proud of the housing. I measure both the bearing recess and the bearing and the difference is about 3/16″, the bearings are definitely completely seated in the housings. I’m assuming that this is intentional but am going to call Moser on Monday morning to confirm. I’m also going to ask them about the quality of the bearing retainer plates that, uncharactersitically, seem pretty wimpy to me.

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