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 4 - Teraflex Low20 Kit & Case Grinding

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Tera Low Low-20 Kit

The kit arrives well packaged in a single box.
It includes a third-party gasket and seal kit from Crown Automotive - pat number J8130995 for the Jeep D20 application.  The seals are useful, but the gaskets are junk - none of them fit properly and you may as well throw them away right now.  No big deal - you want to use silicone anyway.
Box label and part number.
The gears are well protected by form-fitting packing foam.


The gear set all laid out.  From left to right:

  • Rear sliding gear (TL20-E)
  • Main drive gear (input gear) (TL20-A)
  • Intermediate gear (TL20-B)
  • Front Output gear (TL20-C) on top of front sliding gear (TL20-D)

In the foreground are the new intermediate gear thrust washers, needle bearings, and the new intermediate gear shaft.


Detail of Tera Low intermediate gear and front gears.
Detail of rear sliding gear and main drive gear.
The complete kit.
Comparison of the old drive gear installed, and the new Tera Low drive gear in hand.

Clearance checking and case grinding

Most Dana 20 cases will require some minor clearance grinding to fit the new, larger rear sliding gear.  Place the rear sliding gear in the case and then put the output housing in place so you can place the sliding gear on the rear output shaft.
You will have to check for clearance and mark the case for any required grinding through the entire range of travel of the rear sliding gear - from all the way to the rear of the case, as shown in this pic...
... to all the way towards the front of the case, on the shaft, as shown in this pic.  If you don't do this, you could find yourself clearancing the case, assembling everything, and THEN finding out that the sliding gear will not slide properly.  Ask me how I know!
Rotate the rear output shaft and check where clearancing is required between the gear and case.  Yellow arrow shows the general area.
After rotating the gear in the case, the slight contact between the gear teeth and the case left noticeable marks in the casting flash of the case (yellow arrows), making it easy to know where to grind.
This view, from the rear of the case with rear output housing removed, shows the ridge that needs to be smoothed out (yellow arrow).
Shot of the lip smoothed down with a die grinder.
Close up shot of same.
With the rear sliding gear all the way to the front on the rear output shaft, slight grinding of the hump may be required.  Here you can see the gear teeth just contacting.
Clearance grinding complete
Here you can see the final spot that needed a little clearancing...

... and the finished grinding.

The grinding involved was quite minimal, and only took a few minutes with a small air-powered die grinder and a couple of different shaped grinding stones.  I used a cone shaped one and a cylinder shaped one.

When you're done, it is ESSENTIAL that you thoroughly clean the entire case and any parts in solvent and dry them.  You do not want any grinding dust to find it's way into the bearings or between the gears.

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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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