Specifications

26
dana 18 & 20 t/c adapters (1941-79)
ADAPTER CROSSMEMBER SUPPORT:
The early Jeep vehicles were equipped with a single channel-type crossmember that mounted directly
to the frame rail with two bolts on each side. The mount had approximately a 4" drop from the bottom
of the frame rail and provided a pad for positioning the transfer case support donut. The donut gave
the transfer case additional support and flexibility which prevents it from splitting. It is important that
you retain this donut location with the same type of support. If the transmission mount is moved on
the crossmember, then the transfer case mount location will also need to be relocated. On conversions
that are going to move the drivetrain closer to the driver's side of the vehicle, we suggest that the
crossmember end on the driver's side be shortened and welded back to the passenger side. This will make
sure that the relationship between the transmission location and transfer case support is retained. The
crossmember may need to be positioned downward off the frame rails on certain conversions. This can be easily
done by using an aluminum spacer block between the frame rail and crossmember. The original skid plate should
be maintained for maximum offroad protection.
In the early 1970s, Jeep started to incorporate the crossmember and skid plate into one unit. This skid plate has been manufactured
in various widths and configurations for the different models of vehicles. The crossmember/skid plate combination can be easily
adapted for most engine conversions. With a little planning and minor modifications, you can retain the original transmission support
location to assure maximum offroad protection. When changing transmissions, it may be necessary to cut away the front portion
of the skid plate for additional front driveshaft clearance. The transmission support should be retained in its entirety. The long arm
off of the transmission mount must be retained with the rubber snubber in order to limit the movement of the transfer case. Without
this rubber donut, the transfer case will be permitted to over rotate and contact the skid plate. The skid plates used have all basically
been the same, while the transmission support mount has had numerous variations.
When changing to different transmissions, we have provided a support mount area on the bottom of the adapter housings. This
mounting area may not be identical to your original transmission, and a small adapter plate or bracket may be required on certain
applications. We offer a crossmember mounting bar, Part No. 716017, that will adapt the new housing to the original transfer
case skid plate support mount. The skid plate can be spaced downward from the crossmember if additional transmission and tunnel
area clearances are required.
Most of the adapters we manufacture offer a support pad machined on the casting. The location of this pad will normally require
you to relocate your crossmember on your frame rails or reposition the rubber mount on the crossmember. We offer a few options
to aid you in this area.
P/N 716003 - New rubber support (Jeeps 1941-79)
P/N 716021 - New rubber support (Jeeps 1972-79)
P/N 716017 - Aluminum adapter block (used to help retain your stock rubber support)
DANA 18/20 TRANSMISSION-to-TRANSFER CASE ADAPTERS
The Jeep Universals and Scout transfer cases from 1941-79 all had the same Dana 18/20 transfer case bolt pattern. There has
been variations to this such as large hole transfer cases and small hole transfer cases, shift linkage, and drive gear variations. We
manufacture the complete transfer case product line so that they can be interchanged with the various designs. It is VERY critical
that you use the correct alignment bearing retainer when bolting our adapter to your transfer case. In the photos on the previous
pages, you will be able to see the differences between a small hole and a large hole transfer case. If the transfer case drive gear
can be removed from the front side of the transfer case, then it is a large hole design. If the gear has to be removed from the back
side of the transfer case, then it is a small hole design. Small hole designs are limited to only Dana 18 transfer cases, while large
hole transfer cases can be either a Dana 18 or Dana 20. The Dana 18 transfer case has the output power OFFSET to the passenger
side of the rear axle, while the Dana 20 has the output power directly IN LINE with the transmission.
Alignment retainers: When replacing a T90 3 speed transmission, you must remove the bearing retainer from the backside