Your 90 most likely has Borg Warner 1354 Electrical
Ranger, Bronco II & Explorer 1990-2004
A 1354 manual can be swapped in with shifter, etc pulled from a yard queen.
Read this by snoranger;
"The T-case is 3 parts...
The front plate... there are 3 different ones:
Early model (only used on the 13-50). It had standard bolts to attach to the trans and a 4 gear planetary. This is the weakest plate made.
Later model (used on 13-50 and early 13-54s). 4gear planetary and drilled for metric trans bolts. Stronger casting.
Newest model (used at least up to '01). 6gear planetary... Metric bolts... Similar casting to the previous model. (This is the plate I would use.)
The front half:
The Only difference between the E-shift and manual shift front halfs:
The manual case is drilled for the shift shaft, detent ball and spring, and the sensor.
I don't have the specs anymore, but here's the best of my memory.
There's a flat spot (possibly a recess in the casting depending on the year.) where the shift shaft should come through. This has to be drilled out and reemed to a few thousandths over the diameter of the shaft. (It must be reemed for a smooth surface for the o-ring to seal.) Then you have to drill the same area 90 degrees to that hole for the spring, detent, and sensor. I drilled all the way through and tapped the bottom for a 1/8 pipe plug. That made it easier to assemble the detent and spring. The top has to be tapped for the sensor... I can't help you with that, I never bothered.
Use an aluminum 2/4wd shift fork from a 13-50 to replace the plastic fork used in most 13-54s ( not all. I don't remember what year they switched.)
Use the 6 gear planetary found in the later 13-54 (ford changed to this around '94 or so.)
Use the better high/low shift fork and hub found in the later 13-54. (It's hard to explain, but if you see the 2 different styles, go with the "disc" style.) you may have to use this style with the 6 gear planetary... I can't remember for sure.
Check the pump and case carefully. The pump goes in a groove on the rear case to keep it from spinning. If either has wear... Don't use it. These pumps are known to spin (either from the case or the pump wearing out. Piss-poor design.), when they spin the pickup hose breaks and it stops pumping. Good bye T-case.
The rear half: To convert an E-shift rear half to a manual half. Cut the long stem for the E-shift shaft off (inside the case, you can't miss it.) Drill and tap the remaining hole and install appropriate size pipe plug.
The 4gear isn't much weaker, you can use it if that's all you have. If one of the cases has the 6gear, use it. The front plate must match the planetary. Don't even remove the planetary from the plate, unless you want to replace the bearing or the seal.
If you can reuse your manual case housings... Do it. If you can't... Now you know how to modify the E-shift case to work.
If you've rebuilt engines, you don't need a "how-to" on rebuilding a 13-54... They are dead simple.
Open up your spare case... You'll see how simple these cases really are. If your in a real bind... Pick up a cheap E-shift case to throw in the truck as a temporary case to be able to drive the truck. Any 13-50, 13-54, 44-05 will bolt in and give you 2wd."
Or purchase this NOS OEM Ford Ranger Explorer Bronco II Transfer Case Shift Motor 1990-1995 - eBay @ http://www.ebay.com/...5-/271764247487
Troubleshooting the Borg-Warner 1354 & 1356 Transfer Case Control Module - ATRA @ https://www.google.c...EZGw6aHVABRheTQ
Electric Shift Motor Typical Failures & Prevention; "...Most units fail because of water or mud intrusion. Carefully inspect motor boot or protective coverings. Be sure connector seals can keep water and debris out. Check wiring harness and connector. Replace or repair wiring as necessary. After installation, periodically select 4-wheel drive mode to ensure operation when needed..." by Cardone
This is for full size Broncos with Borg Warner 1356 transfer case:
1356 Electric Shift to Manual Shift Swap in a 95
Source: by Shadofax (TheJuice, The Juice, Mark Z)