rotation or 2" up rotation on the NP205 is the customer's option
for no extra charge, other rotations are possible but may incur
above is a Ford 203 to Ford 205 (#FU4001)
Doubler kit is intended for the "do it yourself" user and
includes all the parts necessary to mate your 203 gearbox
and your NP205 transfer case. These parts are a splined
and heat treated adapter shaft to install in your 203 range box,
a new heavy duty adapter housing, and the necessary gaskets,
seals and hardware. We provide an oil fill and the breather port
for the 203 range box.
The Doubler has proven to be an extremely tough system. The all
gear construction means that most vehicle's weak point is not
the transfer case. If anything is going to fail in the transfer
case, it's most likely going to be an NP205 output shaft, and
those sure don't break easily.
About the 203 rangebox:
The NP203 chain drive transfer case is widely regarded as junk. It does have its problems but by using only the "range box" gear reduction unit, you eliminate those problems. Our kit only uses the front 6" of the NP203, the chain drive and the original differential unit are thrown away. The reduction unit uses large 2 to 1 ratio, helical gears like the famous NP205 and is packaged in a compact housing that bolts easily to a variety of transmissions.
Since the Doublerô adapter is meant to bolt behind an NP203 range box, the first thing you need to do is get a 203 that will bolt up to your transmission. We're going to walk through the steps to mate the NP203 to the most common transmissions in use today. In general you have to look at three things when mating a transmission and NP203. The first is the transmission output shaft, the second is the NP203 input gear, the third is the adapter housing between the two.
A less popular auxillary method of attaching the NP203 to the TH350 is to use the TH350 with a longer output that was originally used with an NP208. You will use the 27 spline input in the NP203 to mate to this shaft and use the TH350 to NP208 adapter housing. This requires drilling and tapping new holes in the front of the NP203 to bolt it up in place of the NP208, and may require very minor machine work on the NP203 input bearing retainer. The drawback of the second technique mentioned here is that the factory TH350 to NP208 adapter housing is about 2.5" thick so your overall drivetrain length will be longer than using the factory 1" plate.
R4 / 4L60E Automatic Transmission:
2: Use a spacer (click here) with a factory TH350 to NP203 adapter. This method is longer and has one more spot to leak but if you aren't tearing apart the transmission and don't need the absolute shortest setup this is a good way to go.
3: use the factory TH700 output shaft and the factory TH700 to NP208 adapter housing with a TH350 version NP203. You will have to re-drill and tap holes in the NP203 gearbox to be able to bolt it to the original NP208 adapter housing. You may also have to do minor machine work on the input bearing retainer on the NP203.
1: Use a factory configuration. The TH400 was available with the NP203 in heavier duty trucks (3/4 and 1-ton generally) in approximately '78-'79. The factory configuration uses a 1 3/8" stickout 32 spline shaft in the TH400, a 32 spline input gear in the NP203 and a 1.1" adapter plate between the two, somewhat similar to the TH350 adapter plate. This is the shortest way to mate the TH400 and NP203.
2: Use a TH400 that originally had an NP208 mated to it. This TH400 uses a 32 spline shaft that sticks out of the case about 2.5" and has an adapter housing that's about 2.5" thick. You'll use a TH400 version 32 spline input gear in the NP203 and re-drill and tap the face of the NP203 with the round bolt pattern to match up to the NP208 adapter housing. Benefits of this kit are the parts are quite common since the NP208 was very widely used with TH400 trannies. The drawback is the adapter is about 1.5" longer than the shorter factory configuration.
3: Use a TH400 that originally had a NP205 behind it. This TH400 uses a 32 spline shaft that sticks out about 4.5". You'll need to use a factory TH400 to round pattern NP205 adapter housing that is 4" thick and once again, re-drill the front face of the NP203 to match the round pattern. The input gear will be the TH400 version NP203 32 spline input. Drawbacks to this system are the overall length with the 4" housing between the two and the expense of buying the factory housing. They're not common as used parts and typically must be purchased new. ORD can supply this adapter.
GM 4L80E 4
speed Automatic transmission:
GM SM465 4
speed Manual Transmission:
1: Use a factory configuration. GM mated the NP203 to the SM465 in 1973-1975 using the 10 spline output in the 465, a 10 spline female input in the NP203 and a 4.25" adapter housing between the two. This configuration was used in a wide range of GM trucks but is somewhat rare. Problems are the 10 spline connection tends to wear in the long term and it's difficult to find. Positives would be the short length and the ability to use the common 10 spline output in the transmission.
2: Use a SM465 that was originally mated to an NP208 transfer case. This 465 will have a 32 spline output shaft with a 8 3/8" adapter housing. You'll use a NP203 gearbox with a 32 spline input gear and the face of the 203 drilled and tapped with the GM round bolt pattern to match up to the factory 208 adapter housing. This works very well if you have the available length in the vehicle since the parts are commonly available and the 32 spline connection is very strong and durable, we have brand new adapter housings.
3. Use the factory SM465 to NP203 adapter housing or a brand new adapter housing that we can provide with ORD's new 32 spline SM465 output shaft and a 32 spline input gear in the NP203 (click here). This allows the shortest overall length with the highest strength, most durable spline connection.
speed Manual Transmission:
Transmissions (most types):
Transmissions (most types):
ORD can supply many of the factory adapters, availability can be a problem with used adapters but we always keep our eye out for the parts to make a Doubler work. About all you can do is call us to check if we have what you need.
Once you have a 203 ready to bolt to your tranny, you can move on to choosing your adapter and transfer case.
The only 205 choice for use with the Doublerô in GM or Dodge applications is the TH400 version 205. This transfer case uses a 32 spline female input gear for maximum durability and strength. If you don't have or can't find a TH400 version 205, Offroad Design has the parts to convert your SM465 or TH350 version 205 to a TH400 type. If you have any other GM or Dodge NP205, see our "NP205 Tech info" section for more information on converting your NP205 to work with the Doublerô. Ford Doublerô kits use any married Ford NP205. All the married Ford 205's came with the correct input gear and bolt pattern to work with our kit. Click here for more conversion kit price info.
The overall length of the Doublerô is now 21.5" for all versions. This is measured from the front face of the 203 to the rear yoke centerline on the 205. This is the same length as the original 203, and only 6" longer than original GM 205 applications. It's 9" longer than a 205 for the Ford guys. The new compact length allows the Gen2 Doublerô to fit in many more applications while still leaving adequate rear driveshaft length. Keep in mind these measurements are not absolute, they can vary as much as 1/2" either way depending on the case length variations and yoke length. This does not include the adapter between the transmission and NP203.
Custom rotations and Hybrid applications This is some pretty cool stuff! The GEN2 Doublerô allows us to mate different brand 203 and 205 transfer cases and to rotate them to some pretty crazy angles for more ground clearance on extreme vehicles. Check this link to see pictures and descriptions.
The installation of the Doublerô can be broken down into steps. The first is disassembling your NP203 and installing the new adapter parts. The second is actually installing the gearboxes in the truck.
Removing the range box from the NP203 is not a difficult project at all. You need a 9/16 wrench or socket, a hammer and something to drive out a 3/16 roll pin. More exact instructions are included in the kit but the summary is to unbolt the aluminum differential housing, remove the differential shift fork, unbolt the chain case and take it off the range box. Thatís all.
Installing our adapter shaft involves removing one external snap ring from the factory 203 shaft (snap ring pliers will be needed), installing the shaft bearing in our adapter housing, transferring the gear and shaft assembly to the new housing and re-installing the snap ring. At that point, you can bolt the adapter housing to the range box and itís ready to go in the truck.
Installing the cases in the vehicle is just like installing factory parts. You bolt the 203 range box to your transmission and then bolt your 205 to the Doublerô adapted 203 just like you would bolt it to a transmission adapter. Thatís it!
The Doublerô is shifted just like your 205, you should be stopped and transmission in park or neutral. You can run with just the Doublerôin gear to give you a 2:1 reduction in 2 wheel drive or use any of the standard positions in the 205 with the Doublerô in high or low range. Any combination of gears in the Doublerô and 205 will work with the highest being high and high for a 1:1 road gear, and the lowest being low and low for a 4:1 offroad gear. We recommend that you use the low gear in the 205 any time you want a 2:1 low gear in 4wd. Using 4wd Hi in the 205 and Lo in the 203 gearbox is the only way possible to break the intermediate shaft. You should avoid this situation.
Our Doublerô twin stick shifter locates both of the shifters in the same hole in the factory location. One shifter will operate the NP203 and have Hi-N-Lo, the other shifter will operate the 205 with the stock shift pattern, 4HI-2HI-N-4Lo. Our twin stick shifter is heim jointed, uses urethane bushings for the pivot points, and comes with a floor boot and proper hold down rings. The current price is $185.00. Here is a photo of our shifter kit:
Our NEW 3 stick shifter uses one stick to shift the 203 gearbox and 2 sticks on the NP205, allowing individual control of the front and rear drive shift rails. This gives smoother shifting characteristics and with the proper internal modifications to the NP205, will allow easy access to front wheel drive and rear wheel low range. This allows you to use the full potential of your transfer case for maximum maneuverability. Price for the 3 stick is $289 and includes floor boots and all the parts shown.
Shifters are available for most Doubler kits, including GM-GM, Ford-Ford, GM-Ford, all Dodge applications, and more.
The Doublerô is not an afternoon bolt-in due to the number of details involved. Some things that will need to be addressed are:
final gear ratios available with the Doublerô (usually over 100
to 1) will give you much greater control of your vehicle in
tight off road situations and much greater torque available for
climbing and crawling. Automatic tranny owners should also
experience their first compression braking off road.
This came from one of our customers from 2003, the adapter and Doubler shaft were unharmed. They are still running to this day, with a new NP205 case of course. *NP205 failures like this are rare, it's the strongest t-case out there, but failures in our adapter housing are non-existent*
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