-Ford 8.8 Axle Swap
created: June 2008
last updated: Aug 12, 2010

Ford 8.8 Axle

The YJ is known for having weak axles, especially the Dana-35 in the rear. Everytime I went rockcrawling there was a constant worry in the depths of my mind that it was going to fail on me. There a couple of solutions available to remedy this situation, and after much reading and investigation I decided a Ford 8.8 swap was best for me. Not only will you get a stronger axle (said to be stronger than a Dana-44), but you get disc brakes, and as an added bonus the 8.8 has the same 5x.4.5" bolt pattern.

Out of habit I took a few pictures when doing this axle conversion. I had never intended on writing a tutorial about it, so I will just throw in some of the pictures to look at. There are plenty of other places to find great information; Jeepz.com Guide, Obi-Wan's Install, Stu-Offroad, a good parking brake solution, or Jeep Forums just to name a few.

After all the fitting and welding was complete, I sprayed on several layers of primer and then finished it off with some high quality black spray paint.
Now it iss time to go scratch it all up on some rocks!

Update: Brake Problems Arise

After two years of driving with this setup, I eventually ran into some issues with the braking system. When I did my initial research on the 8.8 conversion I read about some people doing upgrades to the braking system as well; parts such as the master cylinder, proportioning valve, and/or the brake booster. Then there were the people that left everything stock and didnt have any problems. I was one of those people that left the braking system stock.

Without getting too deep in details on how a brake system works, the problem I ran into was that my stock proportioning valve wasn't designed to pressurize rear-disc brakes. Since the rear brakes weren't getting adequate pressure, it left the front brakes to do a larger majority of the stopping. I ran into a situation where I kept getting front caliper failures, after the second time it happened I eventually had a mental flash as to what was happening.

To fix the problem I replaced the proportioning valve with one from a ZJ, ZJ's come equipped with 4-wheel disc brakes so that means the proportioning valve is designed to correctly pressurize the rear disc brakes. During my initial research I took note that the Jeep's master cylinder can be replaced with one from a Ford E-350 (their 1-ton van), and that it is almost a direct bolt on. The Ford MC has a larger bore and is able to apply more pressure to the brakes. Since I had the proportioning valve off I went ahead and replaced the MC as well.

To make the Ford MC fit, three (easy) things need to be done:
1st) The bolt holes don't quite line up. I found the easiest thing to do is get a good file and file the holes inward a little.
2nd) The "tabs" need to be ground down. Shown in the pictures below.
3rd) The stock Jeep brake line connections are a different size then the Ford MC's. To make the Jeep's fit I just simply bought some brake line adapters. But if you wanted, you could cut the existing lines and then re-flare them with the correct fittings.

Parts Used:
Ford Master Cylinder: 1985 Ford E-350 V8, part # 102008 or M2008 (depending on where you get it)
Brake adapters: 1/4"(female) -> 3/16"(male) and 11/16"(female) -> 7/16"(male)
Proportioning valve: Jeep Grand Cherokee (ZJ) 1994-1998

The enlarged bolt hole and grinded down tab Brake connection adapters Installed