9.1 - IRS/Dana44 Gear Swap ( John H,
December 2, 2003
A while back I asked the list for info on the Dana 44 and the jag rear.
The replies inferred that they had heard they were the same but no first
I have just completed changing the ratio on a jag IRS unit that came out
of a 68 420G from 3.54 to 3.07. I bought a used gear set with the carrier
from e-bay for $15, US variety from an international scout. I also bought a
jag dana 44 set up kit , about $75(precision gear).
The pinion from the US variety is slightly different. The jag unit has
10 splines, the US pinion has 30. Because the jag drive shaft rear universal
joint is the same as some Chevy's, and the Dana 44 is used in some Chevy
trucks, this problem can be solved. Put a spicer # 2-4-2461X yoke on the
pinion and remove the companion flange on the rear of the drive shaft. The
rear u-joint is held to the yoke with u-bolts Napa 329-10. The rear joint is
a Napa 369.
The ring gear is also slightly different. The jag unit is tapped for
7/16 NF. the US unit is tapped for 3/8 NF and this is the size of the bolts
supplied by precision gear. Grainger sells motor bushings for 3/8 to 7/16 to
take up the slack. You can re-tap the ring gear to 7/16 NF, or tap in a
couple of allen screws at 180 degrees to locate the ring gear and let the 10
bolts hold things together.
The carrier came with the gear set so I thought I may as well look an see
if this would work. Forget it, the axle splines are different.
The diff setup kit was almost perfect. The kit came with both bearings
for the pinion. The inner one was right, the outer was too small. I had to
destroy the inner bearing to get it off te used pinion. Also the pinion
depth shims were mangled when I drove the inner bearing race out. New shims
are in the kit.
Everything else went fine, measure the old pinion shims and with the
etching # on the pinion determine what you have to put back. This will
eliminate the step requiring a special dana 44 tool. The pinion drag is
adjusted by the # of shims between the inner races. It is set up much the
same as a wheel bearing with no adjuster nut and cotter key, rather shims in
the middle and the pinion nut at 100+ft/lbs.
The yoke comes with a dust protector to make the pinion seal last
longer. If you want to keep it you will have to grind a small amount of the
diff. casting away or simply drive the dust protector off the yoke.
You will need a dial indicator and magnetic base(backlash), torque
wrench(pinion nut), a big puller(companion flange), regular tools and lots of
If I knew then what I know now I would buy a new gear set for a dana44
and a diff set up kit for a Jag. The dana 44 gear set is about $150, one from
a jag supplier with the 10 spline pinion it is over $400.