Teraflex Manufacturing Dana 20 Low Range Kit

Part 2 of the Uber-20 project
(Building the ultimate low geared transfer case at home)
By BillaVista

Page 3 - Dana 20 Teardown part 2

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Dana 20 Teardown (continued)

Remove the rear output shift fork set screw with an Allen wrench.
Rotate the rear shift rod 1/4 turn to free it from the shift interlock pill (this is the capsule shaped pill that rests between the 2 rods, preventing the stock case from being shifted into 2 different ratios front and rear.) Then, grasp the rear shift rod cap at the rear of the case with pliers, and twist / pull it free (it is just a press fit).  Then take a brass or other soft punch and drive the rear shift rod out of the case from the rear.  As you drive it out, catch the detent spring and ball as they come out of their housing.
Removed shift rod and poppet ball.  Note on the shift rod, from left to right, you see the shift fork set screw detent, followed by the three gear selection detents.  The interlock detent is not visible in this shot.
With the shift rod removed, remove the shift fork from the case, noting its orientation for installation.
Next, remove the front output housing from the case, catching the front shift rod poppet ball and spring as you do so.  If you look at the shift rod holes in the housing from the rear (the face that mates to the case) you can see the interlock pill where it sits in the housing between the shift rods (red arrow).  You may have to tilt the housing side to side so it is visible through the shift rod holes.
You are now left with just the front shift rod protruding.
Remove the front output shaft bearing cap from the rear of the case.
Be careful not to lose or damage the delicate shims between the bearing cap and the case (blue arrow).
Rear of front output shaft, under bearing cap.
You should now be at this stage here.
Using a hammer and brass or wooden drift, strike the front of the front output shaft and drive the front output shaft towards the rear of the case, then remove the bearing cup (race) from the cone (bearing).
You should now have a transfer case that looks like this
Remove the front output shaft rear bearing from the shaft using a bearing separator and harmonic-balancer type puller.
Now comes the only slightly tricky part of the whole disassembly.  You have to remove the front bearing from the front output shaft.  I used a small bearing separator to get behind the bearing, inside the case.  I then used 2 small c-clamps to hold the bearing separator against the front of the case...
... and then used a brass drift to drive the output shaft back through the case , separating the bearing from the shaft.
The shaft can then be removed through the rear of the case.
Detail of the removed front output shaft.
Once the shaft is removed, you can remove the front output gear and front sliding gear from the case.

Shaft in the background, foreground showing from left to right (rear of case to front)

  • Front sliding gear
  • Front output gear
  • Washer
  • front bearing
Components of front output shaft assembly in the order in which they are on the shaft when assembled.
Case now looks like this
Remove front shift rod set screw
Pull shift rod from case, and disengage the front shift fork from the shift rod
Detail of shift rod removed from case, with shift fork reinstalled.  To the left of the shift fork is the detent into which the set screw must index on assembly.
The final step of tear-down is to remove the main drive gear (input gear) from whatever it is attached to - in my case my doubler adapter.  I used an impact wrench to break the nut loose...
... and then a gear / bearing puller to separate the gear from the shaft.
Once it is loose, remove the main drive gear from the shaft.

Once everything is torn down, carefully clean and inspect all parts, ready for installation of the Tera Low kit.  You want to thoroughly degrease the case so that any grinding dust created when you clearance the case for the new rear sliding gear does not get trapped and form a grinding paste.

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Contact Info:

Tera Manufacturing, Inc.

5251 South Commerce Dr.
Murray, UT 84107-4711
phone/801.288.2585 -- fax/801.288.2571



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