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Swapping an Early Bronco Ford 9" into a YJ

...and rear (note how close the lengths are)

by Chris Waterman

EB Swap

Main
Ford 9"
Dana 44
Spring Over
Final Notes

The early Bronco Ford 9" rear is an excellent upgrade for a Wrangler YJ. The early Bronco Ford 9" has a larger ring and pinion, larger c-clipless axle shafts, removable third member, inexpensive locker options, and is available in a wide range ring and pinion ratios. The Ford 9" uses a 9" ring gear where as the Dana 35c uses a 7 9/16" ring gear. The Ford 9" does not use a c-clip axle like the Wrangler Dana 35c used after 1989. The early Bronco Ford 9" uses a 28 spline shaft and after market shafts are available with 31 splines.

The Ford 9" also features a removable third member, so ring and pinion can be set on a bench without removing the entire axle housing. A wide range of ring and pinion ratios are available for the Ford 9".

The only real disadvantage of the Ford 9" is the slightly lower pinion. The Ford 9" pinion comes out lower relative to the housing compared to Dana axles. This hurts clearance a bit and causes a slightly larger drive shaft angle.

Preparation

Rear end parts after tear-down.  Nice shade of green, eh? The first step of prepartion was to take apart the axles and neatly file the parts into bags. I planned on keeping the large 11"x2" drum brakes in the rear, so I made a sketch of how the springs in the rear drums went together.

Pearl of wisdom: Never throw out anything during a project like this until at least a few months after it's all done. .
The next step was grinding off the spring perches and brackets. This was done with a grinder and the rear was not nearly as difficult as the front. After the axle was disassembled and the brackets and perches were ground off, I took all the metal parts I was going to re-use down to a local metal cleaning place and had them stripped. Everything with a bearing race or machined surface in it got chemically stripped, and the rest, like the knuckles and rear end housing, got sandblasted.

Fresh from the cleaners I wouldn't recommend the sand blasting, it took a long time to get all that bloody grit out of the axle tubes. It collected in there on the thin film of old gear oil that was still inside. Anyway, aside from that the results were incredible! Those parts looked absolutely brand new - it was almost scary. The chemical stripping process removed all the grease and rust from the carriers, spindles, etc. without removing any uncorroded metal at all, which is important for those kinds of parts.

Gears and Bearings

Grant Klavatalks, a local truck guru and mechanic, set up the gears in my 9" third member and installed the LockRight locker. A that point I wasn't interested in fooling around with gear setup, and no one else I knew could show me how it was done, so I had a professional do it. He found that the ring gear was badly worn, so in went a new R&P, and out came another $300 Cdn from my wallet. Ouch. Along with the new ring and pinion went new carrier, pinion, and wheel bearings.

Grant was kind enough to swap the carrier in my 9" with a four pinion model that I'll need as and when I upgrade to 31-spline axles shafts. The holes in the stock carrier are too small to accept the larger diameter 31-spline axle shafts.

One other thing I learned around this point about the EB 9" is that the four studs at each end that hold the backing plate and axle shafts on are 1/2" diameter on most axles, but that some have 3/8" studs. This matters when buying axle shafts, so be sure you know which you have. Mine were the 1/2" ones, FWIW.

Spring Perches

Rather than fabbing up spring perches, I bought two pairs of adjustable clamp-type perches from Lou Feger's Racing (p/n 20232-1) in the US. This let me get my pinion angle and fine-tuned after the axle went into the Jeep. Since I was doing a spring over, I just pointed the pinion at the transfer case yoke (under load) and used a CV drive shaft.

Brackets

On the rear axle, I fabricated some shock mount brackets from a piece of square tubing. The track bar was simply left out. Running without the rear track bar change the on-road handling characteristics, but the Jeep is being built for off-road performance, not street racing.

Rear drum brakes

The rears went together real easy. I used all new parts, including spring kits, adjuster kits, wheel cylinders, and shoes. I bought two lengths of hard brake line and bent them to fit between the cylinders and the tee. Again, keeping the old parts proved to be a good idea, as I needed the old shoes as cores to get the new ones. The sketch of the mechanisms inside the drums was useful here, as were pictures from the service manuals that I photocopied at the local library.

New 11" drums vs. old YJ 10" drums I may go to rear discs later, but I like the idea of all the static friction that drums can provide when you're trying to get your engine restarted on a 45-degree slope. These drums are 11" in diameter, thanks to the fact that I lucked out and ended up with the "big-bearing" style 3300-lb rated 9" rear. They are much larger than the 10" drums used in my Dana 35c and later YJs use a even smaller drum that is only 9" in diameter.

Conclusion

The installation was finished by simply hooking up the vent hose and brake line. On a regular swap, the same drive shaft and shocks could be used, but I was also doing a spring over axle conversion. The details of the spring over conversion of covered in that article. Different u-bolt plates, u-bolts, and brake hose are required for the swap regardless of suspension changes. The changes I made are covered in the spring over article as well.

Rear shock bracket and driveshaft detail

Last modified Wednesday, 01-Dec-2010 09:23:35 MST


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