Transfer Case Doubler

Many people who off road and go trail riding are always looking for better trail performance. Many seek out the better trail performance with lower gears so they modify their transmission and their differentials. If they are still looking for lower gears to slow things down and get more control as they go over large and/or steep rocks they may need to look into installing a transfer case doubler. For those who want to do all of the work themselves, this is something that you can take on, though it is often more than just an afternoon project. You can actually buy a transfer case doubler kit that will make the installation easier because you get everything you need in one shot and this can also be a more economical way to buy all of the hardware you'll need.

If you are ready to install a transfer case doubler the first thing you will need to do is prep the actual transfer cases. Generally this means that you will have to clean and reseal the cases as well as do any twin sticking. Depending on how things look on the inside, you may want to rebuild, as well.

When you open your transfer case doubler kit you will want to start by unpacking all the adapter plates and start putting the cases together. If you're working with a 203/205 you will want to start on the 203 side. You will want to start by reassembling the intermediate shaft into the bearing retainer and then you will reinstall it into the range box. At this point you are ready to coat the inside of the shaft with a wheel bearing grease, preferably with a heavier grease. Now you will reinstall the roller bearings from the disassembled 203 boxes. Now it is time to install the adapter plate onto the 203 side to hold the bearing retainer as well as the intermediate shaft in place.

Now move to the 205 side and start by attaching the adapter plate and then check for clearance for the shift rail. Once you have done this you should grease the intermediate shaft spleens and then joint the two cases together. It's important at this point to make sure that both halves of the adapter are seated against one another and then use a strap to keep them in this position.

Now you're ready to remove the transfer case that is currently on your vehicle, which is probably a factory case. You will need to move your transfer case doubler onto a stable transmission jack at this point and move it under the vehicle carefully. After you have done this you will jack the transfer case doubler into position and then attach it to the transmission output. Make any and all measurements at this point, especially if you will need to replace anything else dependent upon the installation of the transfer case doubler.

Move back to the bench and separate the two cases and remove the adapter plates. You will need to put the adapter halves back together and place it into a press, claming the two halves together. You can choose to do all of your welding while the transfer case doubler is in the press, if you would like, though this is not mandatory. Install the adapter to both cases at this point and silicone everything. When you have done all of this you are ready to clean the transfer case doubler and paint it, if desired.

The transfer case doubler will weigh anywhere from 250 to 300 pounds so you will need to make cross members. The cross members will help to support the weight of the transfer case doubler when installed. You may be able to use the factory cross members, if not you will need to fashion your own to support the weight or you'll lose power and torque.