About a year ago, I really screwed up. I replaced my fuel tank with a
larger Aerotank (see
http://groups.google.com/group/rec.autos.makers.jeep+willys/browse_thread/thread/c01bdd6967296ace/bcc15529ed781197?lnk=gst&q=aerotank#bcc15529ed7811 97).
However, when the tank was full, the rear of the Jeep sagged badly.
Well, it was an '82, and those were the factory springs, so I order
new springs. When installing the new springs, I was installing one
side at a time. When attempting to install the first spring, I
noticed the nub that aligns the spring with the differential sat a bit
further back on the new springs and would not align. "No problem", I
thought. I went around and loosened up the spring on the other side.
Unfortunately, I loosened it too much - the unsupported (but still
connected to the drive shaft) front of the differential spun downward
and stopped suddenly when the driveshaft reached its full extension.

To make a long story short, the differential would have to be
rebuilt. I replaced the seal in the front, but that only stopped the
fluid leak. The differential also made a horrendous noise when
driving the Jeep (coasting was OK). Rather than try to resuscitate
the AMC20, I went to Dynatrac and ordered a new Dana 44.

I described my setup to the folks at Dynatrac. A 2.72 rear end (lots
of road trips), standard wheels, no lift, etc... I stressed over and
over that I just wanted something replace my AMC20 that was a lot more
reliable and lower maintenance. As part of the lower maintenance
goal, I opted for the Ford Explorer rear disc brake option. I also
opted for limited slip.

What I received work, but it was obvious they ignored everything I
said outside of basic measurements. First, they welded shock perches
onto the differential. These were installed right in the path of
where the factory shocks would go. After unsuccessfully searching for
a shock that would fit in the small space between the new position on
the differential and the old position on the frame, I ended up cutting
the new shock perches off with an angle grinder.

Second, they used extra long lug bolts. I guess they were meant for
much thicker rims than the factory steel rims. I had to take a die
grinder and cut them down.

I have no complaints with the fit, and the operation seems solid
enough, if a bit noisier than expected. The limited slip is something
I definitely appreciate. The folks at Control Cables Inc provided an
excellent emergency brake cable that adapted between the Jeep's
emergency brake cabling and the Ford Explorer disk brakes. The
driveshaft angle was well within specs (about 3 degrees).

However, the Jeep's proportioning valve was never designed with a disc/
disc setup in mind. After driving for a while (including about 1300
miles with a U-Haul trailer), I noticed my front rotors were starting
to warp. Investigating further, I noticed that I could never get my
rear brakes to lock up. I then ordered a new proportioning valve from
inlinetube.com that fits in the same location as the old, but is set
up for disc/disc. The only issue now is that my (non-power) master
brake cylinder is either weak or old and, although I stop pretty good,
I have to suddenly hit the brakes in order for a lock-up to occur.
I've heard that sometimes folks upgrade to the Corvette master
cylinder - I'll have to look into that.

In summary, it's good, but I'd have to say over-priced. But if you
want new, they're about the only game in town.

Michael