Here's how I went about adding a Doubler Box to my NP435 and D20.  First, why do this?  Well, mostly because I enjoy driving the extreme trails, but I believe that extreme trails are most easily traversed by an automatic transmission, or if inclined to drive a stick you need at least 100:1 crawl ratio.  I really didn't want to just add a low gear set or swap to an Atlas transfer case, so I decided to do the NP 203 instead.  Here's how it went...

MY OTHER PAGES:
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Links to Other Doubler Pages:

 Chad Lloyds Page
 Chris Waterman's Page
 Pirate 203 How To
 Offroad Designs Doubler
 Wagoneer Machine

First:
    I picked up the NP203 and a NP435 from my local junkyard.  It's a U-pullit yard and has pretty reasonable rates for those willing to work a little to get the parts you want.  The NP435 came from a 1980 2WD Ford F150 and has the following casting numbers on the side:  C 96391-8, and has the 4" square bolt pattern at the rear.  The NP203 came from an unknown vehicle (was lying in the Ford rows, but has GM on the side) and has 344268GM cast into the side.  I already had the T-shift D20.

    I really didn't want to throw money at an existing adapter kit that someone else had developed, but would rather take a little time to understand how all the parts fit together and work with each other.  I also figured I could do it significantly less expensive than the $1200 WH wanted for the kit, we'll see if I was correct.

Second:
    NP435 to NP203 Adapter.  For this I used the existing mount/adapter at the front of the NP203, and the stock NP435 bearing retainer/output housing.  I had the inner lip on the 203 mount fround down flush with the rest of the plate and had the 435 housing cut off right behind the bolt holes.  This allowed my to center the 435 part on the 203 part, redrill the mounting bolts and countersink the holes so it could be mounted to the 435 and then have the 203 bolt up to it.  Make sure you keep the NP435 tailhousing at least 3/4" thick.

Third:
    Once the 435 to 203 adapter was done, I sent the 435 mainshaft off to Moser Engineering for modification.  The Chevy 203 uses a 27 spline input gear and the 435 shaft has to be cut and resplined to fit.  I just had them respline the end section, since I can cut it down here at the house.

Fourth:
    Now I was done with the front part, I needed to adapt the back part.  I checked with AA to see if I could get just the adpter and how much it would cost, but WH has a special agreement and AA won't sell it direct.  I called WH and just got the run around (imagine that???), only Jim can make that decision, Jim's not in right now, I'll have him call you back, 38 days and no call back, think he's gonna call?   I guess I won't go that route.  This is also the decision point for figuring out if I'm going with the NP205 or the D20.  Still not sure, but I have time to figure it out.

Fifth:
   Pending

Here's what it cost me so far:
 

Item	Price
NP203	$80
NP435	$90
Adapter Parts
NP435 to 203 Adapter	$80
NP203 to D20 Adapter
Respline NP435 Mainshaft	$75
Respline NP203 mainshaft
Total

NP435 Adapter Plate	NP435 with Adapter Plate on	NP203 Front Plate	NP435 with NP203 Adapters in place
Back side of 203 plates.  Left is stock and right is my modified version.  Note the holes have been redrilled a litlle different than stock and camfered for the bolts.	Front side of the same parts.  The bolt in the right plate is the ones I'm using. Note I also had to grind off a bit of the front web to clear the 435 bearing retainer.  The raised area has also been ground down.