on Photos to Enlarge)
Adapter parts - Dana 300 Clocking Kit.
Adapter installed on transfer case.
Transfer case prior to rotation.
Marking positions can be a big help.
Close up of shifters grinding.
Transfer case after rotation.
Checking the rock world clearance!
things considered, the Dana 300 transfer case is an excellent choice
for the off-roader. It has a strong cast iron case and a decent
2.62:1 low range, which is considerably better than the 2.03:1 in
the Dana 20 I'm replacing.
addition, the Dana 300 is also plentiful, since there was one put
in almost every Jeep CJ built from 1980 to 1986. It can be "twin-sticked"
relatively easily with available aftermarket kits and even lower
gears are available from several sources. The main problem is that
the 300 hangs down more than the 20.
where the new Dana 300 Rotation Kit from Advance
Adapters comes in. It allows the Dana 300 transfer case
to be rotated counter-clockwise to four positions (prior to publication
Advance Adapters added two more positions to the adapter pictured
in this article for even more versatility).
far you go depends on your vehicle and your willingness to make
needed modifications resulting from changing driveline angles, reduced
clearance under the body, etc. With the right combination of body
lift, transmission clearance, exhaust system, driveshaft angles,
etc., the rotation kit could allow the use of a skid plate that
is virtually flat across the bottom of the frame.
kits (Dana 300 Rotation Kit and the Dana 20 to Dana 300 Conversion
Kit) come with almost everything you need, with the exception of
RTV sealer and a good thread-locking compound. The transmission
to transfer case adapter includes the adapter, new output shaft,
rear seal and snap ring, and necessary seals, gaskets and bolts.
While it's not the intention of this article to go into detail on
this part of my swap, I will point out a few possibly obvious points.
First, read the instructions thoroughly, and follow them! They are
well-written and will save you time in the long run.
if you have a Jeep T-18 transmission like mine, you will need to
drill two holes in the case, as the adapter mounts differently than
the Dana 20 adapter did. Get some help here, both while marking
hole location and in the drilling process. If you have access to
a drill press large enough to hold the trans case in a vertical
position, use it.
if you don't know how to completely disassemble your transmission
(and reassemble it), this part of the swap is not for you!
the other hand, installation of the rotation kit itself is much
easier to install. If you can remove the transfer case and perform
relatively minor disassembly, you can do this. The Rotation kit
includes the adapter ring, longer transfer case input shaft, a sealed
input shaft bearing, gasket and new bolts.
to removing the skidplate, use a jack stand to prop up the transmission
at its normal height. This will help in determining rotation later
on. Also, be on the safe side and engage your parking brake and
chock your wheels.
Once the transfer case is removed, you must remove the input assembly
to install the new input shaft. Remove the six Allen head bolts
and use the two grooves in the aluminum front bearing retainer to
carefully pry out the assembly. An extra pair of hands definitely
Once you have the retainer removed, remove the two snap rings and
take the assembly apart, noting the position of each part.
Replace the input shaft and bearings with the ones provided in the
kit (the sealed bearing isolates the gearbox fluids). Install the
snap rings, line up the 6 counter sunk holes, and reinstall the
retainer assembly back into the case. Use RTV to seal the retainer
to the case and thread-locking compound on the bolts. Torque the
bolts to your vehicle's specifications using a criss-cross pattern
so that the retainer is sucked down evenly.
the retainer is installed, you must decide on how much you are going
to rotate your transfer case. If you positioned your transmission
at its normal height as previously suggested, you can mount the
t-case (without gasket or sealer and shifter assembly), and rotate
to the best position for your application. A suggestion here is
to use a small pin punch on the outside of the adapter to mark the
location of different locating holes. Place these marks where you'll
be able to see them when the t-case is installed.
Adapters advertises rotation to 2 or 10 degrees, but they are referring
to rotation from an absolutely level position, not rotation from
stock position. The latest version of the rotation adapter, with
it's 2 additional location holes, will allow even further rotation,
assuming proper clearance at the transmission, body, etc.
my case, to utilize the first locating hole in the adapter ring,
(which would be the second in the new version) I had to grind material
off the right, rear, upper corner of the transmission case and the
inside of the shifter mounting portion of the aluminum front output
bearing retainer. This gave me enough clearance to rotate my t-case
almost 20 degrees.
also "twin-sticked" the t-case using shift levers from a Spicer
18 t-case. To mount the shifters, I had to file down the insides
of the mount to the proper width, and drill out the shifters to
accept a 5/8" bolt. I also ground a groove in that bolt to accept
a set screw that was drilled and tapped into the housing. At the
bottom of the shifters, I drilled a 1/4" hole to allow them to be
connected to the shift rails.
some trial and error, I used two short pieces of 1/8" flat 1/2"
wide steel, twisted 180 degrees, to bolt to the shifters on one
end and the shift rails on the other. So far this has worked perfectly.
If you want to skip this step, I suggest you contact Currie Enterprises
and have them send you a twin stick conversion kit and shifter boot.
Either way, if you choose to do this modification, you will need
to disassemble the t-case and remove the shift interlock "pills"
to allow the shift rails to work independently of each other. You
will also need to bend both t-case shifters to the right to correct
for the amount of rotation.
can see by the photo that I was able to gain just over 3" of additional
clearance by rotating the transfer case. This placed the t-case
at an almost level position.
you've installed the case, fabrication of your new cross-member/skidplate
can begin. To gain the most clearance possible I fashioned a much
shorter mount from the original metal "outrigger" plate and a piece
of 3/4" thick hard rubber. from a scrap piece of matting used to
cushion the weight room floor of my local health club.
Skid Plate Comparison - The Original Dana 20 Plate, The Dana
300 Plate and the new flat Plate
can use the original mount of a polyurethane version, but it is
almost 2" high, and would result in a lower skidplate or designing
a different mount, altogether. In the next photo above you can see
a comparison of 3 skidplates. My customone, in front, hangs down
only 2 3/4" from the frame. The Dana 300 factory plate in the middle
hangs down over 5 1/4", and the Dana 20 factory plate in back hangs
down 4 1/2". This means that I have increased my over-center clearance
by 2 1/2" ! And, with the exception of my traction bar mount, which
was previously mounted to a separate crossmember, the skidplate
is completely flat!
things to consider: The adapter plate is 3/4" thick. On most vehicles
that won't require driveshaft lengthening/shortening, depending
on your slip yokes. Also, the front angle will increase due to the
rotation of the t-case. In some vehicles, this may necessitate going
to a double-cardan (C/V) style u-joint and yoke. My application
level of oil to fill the transfer case with after rotation will
change, since the fill plug is rotated considerably higher than
stock. In my case, I removed the top left bolt from the cover at
the rear of the front output shaft and used that as my level indicator,
since it was approximately the same height as the fill plug was
was it worth the time and expense? Your application may be different,
but let's think about this. To get that 2 1/2", you would have to
install a taller suspension lift or 5" taller tires. Sure, these
would increase differential ground clearance, but they would also
greatly increase your vehicle's center of gravity as well. For me,
after rolling my previous CJ-7, with 7" of suspension lift and a
2" body lift and 38 1/2" tires, the answer is obvious. With 35's,
6" of suspension lift, and no body lift, with proper tire placement,
I can go pretty much the same places I used to go. You decide!
4320 Aerotech Center Way
Paso Robles, CA 93446
Phone: (805) 238-7000
or (800) 350-2223
Brinks is an avid 4 Wheeler and a new writer here at ROCKCRAWLER.com.
Jack resides north of Houston, TX and frequents many events
in the Southwest.
Jack at firstname.lastname@example.org