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Swapping Early Bronco Axles into a YJ

Before After
Before After

by Chris Waterman

EB Swap

Ford 9"
Dana 44
Spring Over
Final Notes

Who in their right mind would take a perfectly functional 9-year-old Jeep YJ, rip out the entire undercarriage, and replace it with parts from a 25-year old Ford? Chances are if you're reading this then you understand already, but for those of you who don't...

  • Stock YJ axles are a relatively weak link in an otherwise excellent vehicle. If you want to run tires over 31", especially with lockers, then the odds of breaking an axle shaft or u-joint, or even bending a housing, go way up under even moderate usage.
  • The early Broncos, on the other hand, were big, heavy, and thus very solidly built. The stock axles for a 1973 EB were a standard-cut Dana 44 up front and the much-praised Ford 9" in the back. In a YJ they make for a very stout combination and reduce the odds of breakage even with large tires and lockers.
  • The brakes are bigger all around (I've ended up with 11" discs and 11" drums). The axles are about four inches wider than on the YJ, which is nice for a little extra stability too.
  • It was a cool project. Early on in the game I discovered that I couldn't find anyone who had ever done this swap before, so from then on it became a personal challenge. Something about the risk involved appealed to the fool within me. That and I had no idea what I was really getting into. My most ambitious project before this was an on-board air system (not even in the same ballpark) and while I'm mechanically inclined this was way beyond anything I'd ever done before.
Angle view

How did it start?

Before the swap, My Jeep was a relatively stock 1989 YJ. It had 2.5" OME lift springs in it and 31" AT tires, and that was as far as I thought I wanted to go with lift. Then Larry Soo (aka lars) got involved. I remember one conversation:

Larry : "You should do a springover. Hmm... springover with OME springs."
Me: "Uh, yeah, right. Heh heh."

But the seed was planted. I'd wanted to get a rear locker for a while, but didn't like the idea of throwing $$ at the stock D30 and D35 axles after hearing them bashed so often on the Jeep-L and Jeeptech lists.

Some time later, Larry told me about a friend of a friend who was selling a pair of axles from an old Bronco. I went over to see them. They looked terrible! Covered in rust and some kind of green mildew, but the potential was there! The rear end had the stock 28-spline axles, and the front had a standard-cut diff and drum brakes, but the width looked good and they had 4.10 gears in them. Next thing I know, I've purchased the axles and I'm planning a spring over axle conversion.

Ford vs. Dana Ford 9": Preparation and installation of the Ford 9" rear from an Early Bronco into a Wrangler YJ. The Ford 9" is massive compared to the stock Dana 35c.
Dana 44 Dana 44: The early Bronco Dana 44 had 30 spline shafts, 8.5" ring gear, and real hubs. There are many advantages of a Dana 44 front end in a Wrangler or CJ.
Flex Spring Over: Doing a spring over conversion on a Wrangler YJ for maximum articulation. The conversion is a bit more work than a normal lift, but the results are amazing.
Lars Help Final Notes: Some final notes on the spring over axle swap and early Bronco axle swap. Important things like wheel bolt patterns must be considered.

Last modified Wednesday, 01-Dec-2010 09:23:45 MST

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