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Dana 300 Transfer Case Install into a TJ
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By: Chris Krieg- 1/2003

Flipped Dana 300 Transfer Case with Teralow

While my built up NP231 transfer case was a good transfer case, I wanted more strength. I also wanted to retain the 4 to 1 low range that the Teralow in my NP231 gave me. I looked around and, at first was interested in the Atlas II by Advanced Adapters. This is a very nice case, but at around $2100 for the 4.3 to 1 model, it was out of my price range. Then, I found out about the Dana 300.



The advantages of the Dana 300 over the NP231 are:

The big problem of putting a Dana 300 in a TJ is that the front output of the transfer case is on the passenger side of the Jeep. The front differential is on the driver side of the Jeep. To overcome this issue, Downeast Offroad (DEO) has developed the Dana 300 Flip Kit. It allows you to flip the transfer case over to convert it to driver side front output. It also converts the transfer case from a single shifter to a twin stick shifter. This allows you more shifting options in 2 wheel drive and 4 wheel drive modes. I was able to pick up the Dana 300 Flip Kit for $550 in a group buy on the Jeeps Unlimited BB.

The final thing about the D300 that needed to be addressed was that the low range was only 2.8 to 1. I wanted the 4 to 1 low range that I had with the Teralow kit in the NP231. Tera again was the solution for this. They make a Teralow 4 to 1 low range kit for the D300. I purchased one through a group buy from DC Offroad, again on Jeeps Unlimited, for $530.

I also was able to get a deal on a used Dana 300. Arizona Trailwerks, here in Phoenix, allowed me to trade my spare stock NP231 for the D300. It is out of a 1982 Jeep CJ, so the speedo on the TJ will hook up directly to the D300.

I also ordered a Blitz Cranker clocking ring from Cory Morgan in Canada. It cost $160. Mine was for clocking an existing Dana 300 installation so the bolt pattern wasn't exactly the same. You can see how this was solved in the install section. He now makes a clocking ring with the correct bolt pattern to mate the TJ's AX-15 to the Dana 300.

So, for about $1400, I was able to build a stronger transfer case than the NP231. I will also have to have the front driveshaft shortened and the rear driveshaft lengthened.

Follow along as I install the D300 flip kit and Teralow 4 to 1 kit in the Dana 300 and then install it in the TJ.

The Dana 300 project will be broken down in to 3 sections:

Teardown and case modifications (shown below)
Rebuilding
Installation in the TJ

 

   
Humble beginnings. This is the Dana 300 fresh from the salvage yard.   Getting started. This is the input gear assembly. It is held to the case with several allen head bolts.   This is the disassembled input gear assembly. The bearing and gear will be replaced with the new Tera ones.
   
The intermediate gear has been removed. The parts above the gear are the needle bearings. Almost everything here will be replaced by the Teralow and rebuild kits.   The rear u-joint yoke and retaining bolts have been removed from the rear output housing. A few taps with the mallet freed it from the case.   The rear output housing has been removed from the case. This assembly also holds the speedometer gear. The speedo gear opening is the same size as that on the TJ so the speedo assembly from the TJ will fit the D300.
   
Removing the shift forks. The front fork has been removed already. To remove them, I removed the set screws (shown above) and then just pulled the shift rods out of the case. Then the shift fork can be lifted out of the top of the case.   Here, the front output housing is being removed. I removed the retaining bolts and gave it a few whacks with the mallet. This housing also holds the shifters. This will be done different with the flip kit.   Front output housing removed.
 

 
Rear bearing cover plate removed   Gosh, I hope I can remember where all this goes.   To get the rear bearing off of the rear output shaft, I set the case on 2 boards (per the FSM) and used a brass punch to drive the shaft down. The large gear inside the case holds the bearing stationary (it is larger than the hole in the other side of the tcase) as the shaft is driven down. This pops the bearing off.
   
These are the rear output shaft assembly parts. The twisted looking splines on the shaft mesh with the speedo gear. Only the output shaft will be reused.   Shown here is the front output shaft assembly along with the main gear, clutch sleve, and rear bearing. I used my 12 ton shop press to press the output shaft out of the bearing.   Here, I am removing the forward bearing from the front output shaft. I picked up this gear/bearing puller from Harbor Freight.
   
The completely disassembled front output shaft parts. Only the main shaft and shift coupler will be reused.   I punched the shift rod thimbles out of the case using a long socket extension. They will not be reused with the flip kit   The case is now completely empty. Just needs to be cleaned up and some simple mods done for the flip kit and Teralow kit.
   
The first mod I did to the case for the flip kit was to drill out the shift rod holes to 45/64". DEO includes the drill bit in the kit. These holes will no longer be used for the shift rods since this will now be the bottom of the case. They will be filled with brass plugs.   Next, I used the 1/2-14 NPT tap supplied with the flip kit to cut threads in to the enlarged holes. I have already installed one of the brass plugs.  
The second case mod required for the flip kit was to cut the shifter section off of the front output housing. This part is aluminum so the cutting went pretty easy with my Rotozip. Here, I have marked 3/4" down from the shifter holes and made the first cutting pass.
   
This is the front output housing after it was modified. Compare this with the previous picture.   This is the section that was removed from the front output housing. It held the mounts for the shifter. It is no longer needed.  
The second case mod that needed to be done was for the Teralow kit. The new intermediate gear is larger than the original so this area is notched to allow this gear to go in easier.
    The case is empty and all mods necessary for the Teralow and flip kit are done. Now its time to rebuild the Dana 300
The last case modification necessary for the D300 flip kit is to plug the old vent hole in the rear output housing. To do so, the hole is first drilled out to a larger size.   Then the new hole is tapped to the same size and the old D300 drain plug. The drill bit and tap are included in the flip kit.    

On to the Dana 300 rebuild


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