When I started this project, I was sure that I didn't want the single gear full time AWD transfer case that is used in the AWD version of the 5.0L Explorer. I wanted to have a manually shifted, 2-speed, part time 4WD transfer case.
An easy (but expensive) way would have been to get a $500+ adapter kit from Advance Adapters to mate the 4R70W Explorer transmission to the stock Ranger case. The kit consists of a new extension housing and a shaft adapter that steps down from the 4R70W's 31 spline output shaft to match the smaller Ranger T/C spline. That would have also allowed the use of the factory Ranger driveshafts and the factory manual Ranger T/C shift linkage.
It seemed like a better idea to use a larger transfer case designed for the torque a V8, so I got the manual Borg Warner 4406 case used in the F-series and rated at 300 lb-ft. The 4406 bolts directly to the stock 4R70W extension housing without modification but that's where the easy part ends.
First of all, the 4406 transfer case is huge
compared to either the stock Ranger 2-speed case or the stock Explorer AWD case. It is nearly twice as long front to back and the main body sits about 4 inches rearward of where the main body of the Ranger case was. It is also much wider and would sit about 1/4" from the DS frame rail if the stock 5.0L Ex mounts were used. Even worse, the forward U-joint of the rear driveshaft would end up being about a foot farther rearward as compared to the stock Ranger, putting it adjacent and very close to the nose of the fuel tank.
The solution to both clearance problems was to move the entire engine/transmission/transfer case 3/8" toward the passenger side. This was accomplished by welding up the engine plate holes and trans crossmember holes and repositioning them.
These photos show the results of using the modified mounts. There is still not a lot of room there but imagine how it would be using the stock mounting position - 3/8" closer!
Transfer case to frame rail clearance:
Slip yoke to fuel tank clearance:
This is the 4406 shift linkage. It was moved almost 3/4" inward by reversing part of the linkage and by shortening the mounting bosses on the extension housing. Combined with the 3/8" powertrain offset, the mod moves the linkage and lever significantly inward on the transmission tunnel, keeping it from intruding any more than necessary into the driver's legroom.
Here is the F150 silicone inner boot that has been reshaped to fit the Ranger tunnel. The stock Level II shift arm was too short by itself, so I made up an intermediate extension shaft from a piece of 3/4" drill rod.
This is the interior trim boot.
The shifter moved all the way rearward to the 4x4 Low position.
Another clearance issue involved the electrical bulkhead connector under the driver seat. The rearward position and larger size of the 4406 put it too close for comfort. My first idea was to move the square hole forward by cutting and welding. However, it occurred to me that I could accomplish the same thing by angling the connector away from the transfer case. By sandwiching the sheet metal between two large round blocks of steel bolted together, it was easy to reshape the floor and push the connector body away from the t-case.