CJ-7 Projects


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HEI Ignition System (GM Style) Installed in the AMC 360 V8
Getting rid of gremlins and improving performance

Installing 23,000 Volt Offroad Lights

Autogage Tachometer Installation

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 Centralia PA
Project CJ-7
Offroaders Guide
to Gearing up
for Offroad

From Basic Equipment to Well Equipped.  An extensive list guide to help you prepare your vehicle for the offroad.


Onboard Air
Converting a York
AC Compressor
to Pump Air

Trailering Safety and Trailer Hitch Information


Off-Road Truck Driving Techniques and Safety

Off-Road Lights
by LightForce Product Review / Installation.
from Off-Road Lights


Jeep Dana 300 TeraLow - 4:1 Gearset for the Dana 300 Transfer Case

AMC V8 Engines
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Chevy Small-Block V8 Engines Manufactured by General Motors - Production: 1955?2002

Hemi Engine - All about the Hemi Engine

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8 Cylinder Engines manufactured by Ford

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351 cubic inch V8 Engines manufactured by Ford

Chrysler Hemi Engine

AMC V8 hp/Torque, Compression & Bore/Stroke by year

Engine Size Conversion Table
Converting engine displacement from CID, Liters, C.C.

Engine Overheating Basics - 16 Common Causes of an Overheated Engine

Fan Clutch Diagnosis
How to tell if the Fan Clutch in your Cooling System is failing or has failed.

Automotive Gauges & Instrument Functions
Information they display & their importance.


From the
Department of Cheap   Tricks and Useful Tips

Ultra-Cool Hand Throttle for Free!

Jeep V8 Swap Tips

The Exploding Clutch

Radiator Protection using 6 bucks worth of material

Cracked Under Pressure - Fixing a smashed fingernail

A Cheap, effective alternative to undercoating

Home-built Saginaw Gearbox Brace for the cost of lunch!

Ammo Box Storage - Mounting Them for Quick Disconnect

Home-built Serious Skid-Plate protection for the Oil Pan for under 20 bucks!

Ramp Travel Index
RTI / Ramp Travel Index  What it is and how to calculate it, with and without the ramp.





Project Jeep CJ-7
TeraLow Gears
in the Dana 20 Transfer Case

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Disassembly of the Dana 20
Breakdown of the Dana 20 case

Grinding the Case of the Dana 20 Transfercase
Grinding the metal to clear the Teralow gears

Reassembling the Teralow Dana 20
How it all goes back together.

Teralow Dana 20 Reviews
What people think of the Teralow Dana 20 Kit

Crawl Ratio Calculator


Assembly Time


Time to start assembling the Dana 20.  Now is a good time to prep your work area.  I like to use a clean old white towel on the work bench.  For one, it's easy to see parts like small bolts and bearings and it helps keep things from rolling around.  It's also good to be able to lay clean parts on and to keep the paint from getting all scratched up while I drag the case across the bench (I'll wait for the scratched on the trail).   It also helps to have a place to wipe grim or grease off your hands while working.

When re-assembling the case, I followed Teralow's directions.  Their instructions were simple and to the point and seemed to be written by someone who was familiar with assembling a Dana 20. So much so that they seemed to have overlooked a few things like mentioning to place the gasket on the case before bolting the part on and a few other things.  Not a big deal since I didn't forget any gaskets but those are the sort of things I want to mention in this write-up like how to load up the needle bearings.

Teralow's directions start off with sliding the front output shaft shift rod partially into case.  Since I already had my shift rod in place (couldn't get it out), I skipped over these first three steps.

1.   Slide front output shaft shift rod partially into case.
2.   Place front output shaft shift fork on rod with bolt hole aligned with countersunk hole in rod.
3.   Install setscrew and tighten to 14 foot-pounds torque.
4.   Next I placed the rear output shaft shift fork in proper position in case.

5.   The I set the new rear output shaft sliding gear on shift fork with slot in gear facing rear of case.

I questioned whether this step was necessary because I would be working on the other side of the case while this gear would be clanking around in the case.  It might be possible to squeeze it into the case after the other gears in the next few steps are in.  I tries and was able to do it but it might be tight for some.  Probably better to get it in now.

6.   Install rear bearing (Teralow calls it a "cone and roller") on front output shaft.



7.   Insert front output shaft gears, thrust washers, and bearing in place and slide output shaft through both gears.
8.   Install front cone and roller on front output shaft.

I used a piece of pipe to pound the bearing on while supporting it from under with a block of wood.  If you choose to do it like this, make sure you are hitting the inner area of the bearing, not the outer ring.  In fact, it's probably better to do it the right way (whatever that is), not like this.

9.   Install front and rear front output shaft bearing cups.
10.   I installed the rear bearing shims and cover plate, and tightened the cover plate attaching bolts to 30 foot-pounds. 

I added a little silicone gasket sealant and a drop of medium locktite to each bolt just to make sure it didn't back off.  I've occasionally dealt with issues that arose from bolts backing out.  A little Locktite is just a drop of insurance against that.


11.   Using suitable bearing driver (another piece of pipe for me), I drove the front cone and roller onto front output shaft.
12.   Place thrust washer on front output shaft.
13.   Place front output shaft shift rod detent spring in shift rod housing.
14.   Start sliding the housing onto the front output shaft shift rod and place poppet ball on top of spring and depress into housing with a punch as you slide the shift rod past the poppet ball.  Tricky!

You may have to tilt the transfer case to slide interlock to the right.


15.   Slide rear output shaft shift rod into housing far enough to retain poppet ball and interlock pin.  If you can't get past the interlock pin, you have to slide the front shift rod out one click.  I did this with a hammer and a punch, then slide the interlock pin over.


    I used a punch to hold the poppet ball in place while sliding the shift rod down past the poppet ball.  Again, tricky. 

Watch you don't lose the ball if it slipped off the punch!  This is where the towel comes in handy.  Things don't roll well on a towel.

16.   Place large front output gear in case.  



17.   Position rear output shaft shift rod with countersunk hole up and fork engaged in front output shaft sliding gear. Rotate rod 1/4-turn counterclockwise. (to get past poppet ball)
18.   Position and hold shift fork in case and push shift rod through fork.
19.   Rotate shift rod 1/4-turn clockwise and align countersunk hole in shift rod with hole in shift fork.
20.   Install setscrew and tighten to 14 foot-pounds torque.
21.   Install housing attaching bolts and tighten to 28 to 30 foot-pounds torque.
22.   Teralow suggests you attach a dial indicator to shift rod housing to check front output shaft bearing adjustment, then...
23.   Pry shaft to extreme rear position and set indicator to zero.
24.   Then pry shaft forward and read indicator. End play should be 0.001 inch to 0.003 inch which can be adjusted by changing the rear bearing cover shims.
25.   The next step is to assemble intermediate gear rollers and spacers with heavy grease to prepare them to be inserted into the case.

The primary way I know of to pack the intermediate gear with the new rollers and spacers is to use a dowel rod that is just as wide as the intermediate gear itself.  This is placed inside the intermediate gear and rollers and spacers are inserted and packed with heavy grease to hold them in place.

The diameter of the dowel rod is approximately as wide as the intermediate shaft itself.  I hunted around the shed for a donor garden tool and found an old rake that had a handle that was approximately the right width.  I then hacked off a piece at the right length.  I forget what the length and diameter was but you can measure this from your intermediate gear and intermediate shaft. 

I'd like to say that I used this ugly hunk of metal to the right.  It's a slug that was shot out of an A-10 Warthog.  I got it from the Blue Angels at the Reading Air Show years ago.  It was the right diameter but it was just a hair too long to clear the thrust washers.  I didn't want to grind the slug down so I used the dowel rod instead.



    You have three spacers and a pack of roller bearings.

Start by placing the dowel rod into the intermediate gear and packing some grease into the opening around the dowel.  Press a washer into the grease, around the dowel.  Add more grease.

Then start pressing needle bearings into the grease, pushing the washer down slowly.  I believe the magic number of needle bearing is 24.  There should be NO gaps between the needle bearings.

With 24 in, add more grease then another washer.

Add more grease and then repeat the step above and press 24 more needle bearings into the grease.

Follow this up with a little more grease and the last washer.

Before you lower this into the case, MAKE SURE the dowel is not protruding beyond the intermediate gear.  It has to slide past the thrust washers and it's a tight tolerance.

26.   Next place the intermediate gear thrust washers in case the with tangs (tabs) aligned with grooves in case. 
NOTE: Thrust washers fit in case with tangs aligned with grooves in case. Rear washer can be held in place by starting intermediate shaft into case. Hold front washer in position with heavy grease.
27.   Lower and position the intermediate gear in case. 

Using a plastic dead-blow mallet, drive intermediate shaft into intermediate gear.  Start from the back of the case and drive the shaft so the keyed end is out.  Position the shaft so the intermediate shaft lock plate will align with the threaded hole in the case.  Forget about rotating it later.  It won't happen.  Align it first before driving it in. 

Driving the shaft in is tough work.  DO NOT use a metal hammer unless it's one of those lead hammers specifically designed to do this.  A metal BFH like a 5 pound steel mallet will damage the shaft.  It got pretty tough and I ended up using a piece of wood against the shaft and I'd strike the piece of wood with a heavier hammer but not hit the shaft itself directly.  It helps to brace the case from behind as you drive the shaft in.

As you drive the intermediate shaft into the case, the dowel rod will be driven out, leaving the bearings in place.

Eventually I was near the end of the shaft.  At this point a rubber o-ring goes on the shaft. and I continue to drive the shaft in.  This of course splits the o-ring leaving a thin sliver of rubber in my hand.  Hope it don't leak.


IMPORTANT: After intermediate gear is in place, rotate gear and check clearance to shift rail.   Very likely the shift rail will touch the gear and make contact.  If it does you will need to mark the rail and remove it.

Grind the area off the rail enough to make clearance.

28.   Install intermediate shaft lock plate, lockwasher, and bolt. Tighten bolt to 14 foot-pounds torque.



29.   Install rear bearing cap assembly using a new gasket, and slide rear output shaft through gears. Tighten bearing cap bolts to 30 foot-pounds torque.
30.   Install front yoke seal.
31.   Install front propeller shaft yoke and tighten to 100 foot-pounds torque.
32.   Install bottom cover and gasket. Tighten bolts to 14 foot-pounds torque.
33.   Install the new seals.  I used a small piece of pipe to drive the seals on.  The flat side goes out, with the hollow side with the spring around the seal inward.
34.   For the larger output seal, I used a large piece of exhaust pipe to drive the seal on.







Dana 20 Installation back onto the Jeep's T-18

1.   Install new input gear on transmission mainshaft.
2.   Install new transmission-to-transfer case gasket on transmission.

I questioned this area to the right where the seal didn't seem to cover very well.  I think it was a port hole for some other adapter.  Here it lined up with a hole in the transfer case but that went nowhere on the adapter.  It was real close to the outer edge where the upper adapter bolt is.  Potential leak so I gooped a little gasket sealer on it.





3.   Shift transfer case to 4 WD low.  This is so that you can rotate the transfercase gears to align with the input gear on the transmission.


I used a transmission jack adapter for my floor jack.  It worked pretty good for a 40 dollar adapter.


4.   I created a couple of guides.  teralow suggests wooden dowels.  I used the threaded end of a bolt and positioned the bolts so they were at the bottom of the case.  This would help guide the transfer case onto the adapter.


5.   I rotated the transfer case output shaft until the main shaft gear engages the rear output shaft gear of transfer case. Then I slid the transfer case forward until transmission and transfer case mate.


CAUTION: Be sure the transfer case is flush against transmission. Severe damage will result if the transfer case bolts are tightened while transfer case is binding.
6.   Install one upper attaching bolt (snug bolt but do not tighten).
7.   Remove guide bolts and install all remaining attaching bolts. Tighten bolts to 30 foot-pounds torque.

8.   Connect speedometer cable and parking brake cable.
9.   Align reference marks (if you have any) and install yokes (propeller shafts as Teralow likes to call them). Tighten U-bolt nuts to 15 foot-pounds torque.
10.   Fill transfer case with SAE 80-90 Gear Lubricant of API, GL-4 quality to proper lever and check transmission fluid level. Synthetic oil is also recommended.
11.   Lower vehicle.
12.   Install transfer case shift lever, boot, and knob.




Tera Manufacturing, Inc.
5251 South Commerce Dr.
Murray, Utah 84107


Torque Specifications:

Torque Specifications     Foot-Pounds
Front and Rear Output Shaft Yoke Nuts   225-250
Right and Left Shift Fork Setscrews   12-15
Shift Rod Housing to Case Bolts   28-30
Front Output Shaft Rear Bearing
Cover to Case Bolts
Intermediate Shaft Lock Plate
to Case Bolts
Rear Bearing Cap Assembly
to Case Bolts
Lower Cover to Case Bolts   12-15
Transfer Case to Transmission Bolts   28-32


Click to zoom in

Items underlined and bold below are included in the Tera Low20 low range gear kit

1. Shift Rod    33.  Intermediate Gear Shaft
2. Shift Rod   34. Thrust Washer (2)
3. Shift Rail Seal   35. Bearing Spacer (3)
4. Shift Rail Interlock   36. Needle Bearings
5. Shift Rail Interlock   37. Intermediate Gear (TL20-B)
6. Detent Springs         38. Cover Gasket
7. Detent Balls   39. Cover
8. Front Output & Shift Rail Housing Seal   40. Drain Plug
9. Washer   41. Main Drive Gear (TL20-A)
10. Front Output Bearing Race   42. Rear Sliding Gear (TL20-E)
11. Front Output Bearing   43. Set Screw
12. Shift Rail Caps   44. Rear Wheel Drive Shift Fork
13. Case Housing   45. Rear Output Shaft
14. Tranny to Transfer Case Gasket   46. Rear Output Bearing
15. Front Output & Shift Rail Housing   47. Rear Output Bearing Race
16. Front Yoke Seal   48. Speedometer Drive Gear
17. Front Output Yoke   49. Rear Output Shaft Shims
18. Yoke O-ring   50. Rear Output Housing Gasket
19. Flat Washer   51. Rear Output Housing
20. Companion Flange Nut   52. Breather
21. Washer   53. Rear Output Bearing Race
22. Front Output Gear (TL20-C)   54. Rear Output Bearing
23. Front Sliding Gear (TL20-D)   55. Rear Output Yoke Seal
24. Shift Fork Set Screw   56. Rear Output Yoke
25. Front Wheel Drive Shift Fork   57. Flat Washer
26. Front Output Shaft   58. Companion Flange Nut
27. Front Output Bearing   59. Speedo Driven Gear Busing
28. Front Output Bearing Race   60. Speedometer Driven Gear
29. Front Output Bearing Cap Set   61. Speedometer Driven Gear Sleeve
30. Front Bearing Cap      
31. Intermediate Gear Shaft Retainer      
32. Intermediate Gear Shaft O-ring      


Other Teralow Resources:
Great deal on the Tera Low20 from OK4WD
Dana 20 Tera Low20 for Manual Transmissions

Related: Dana 300 Tera Low Install
There are several models of the TeraLow, there are TeraLow's for Dana 300 (4:1), Dana 20 (3.15:1), Dana 18 (3.15:1), and NP 231 (4:1).

Transfer Case Upgrades, Modifications, and Options
Jeepfan.com - There are several modifications that can be performed on a Jeep transfer case.  Most involve replacing the gears in the case to lower the gear ratio to improve slow trail performance.


Teraflex Dana 20 Low Range Kit install / Review
Pirate4x4.Com reviews the Teraflex Low20 Kit including Case Grinding, Installing and testing

Installing TeraLow Gearset - Dana 20 Transfer Case
For hard-core 'wheeling, slower speeds mean greater control and less strain on your drivetrain...Swapping in lower (numerically higher) gears into the axles will certainly help..

Tera Low Dana 20 Gears Review / Install
JeepWire.Com product Review of Tera Low Dana 20 gears.


Project Jeep CJ-7 ~ The Dana 20

Back to Project Index




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Latest trips Offroad
... trail reports with the Project CJ-7
click here.

Sounds System, Raised the Rear Seat
Storage below and a great place to mount 6x9 Speakers for Great Bass ... In a Jeep!

York AC Compressor Conversion.  What used to pump Freon, now pumps compressed air to the front and rear bumpers.  125 psi,  2 gallons of storage, air fittings at the bumpers, enough CFM to power air tools!.  Click Here for more  Details


Dick Cepek's 2008 F-250 Super Duty Project Vehicle ? Project CRUSHER

Warn X8000i
Winch Installation

ARB Air Locker Install
Jeep Wide Track Axles Swap

Mud Tire Reviews

Building a Garage?
Need a Garage Plan?

Reader's Rigs and Seriously Stucks!


Jeep Trans Swap Info
T-18A Transmission Rebuild & Short Shaft Conversion