3-second answer: BW1356 holds 2.2 qt of Mercon ATF (not gear oil). No 4WD + blinking light = the shift motor (rusted contacts inside — clean or replace ~$100). The case itself rarely fails. Service: drain (the plug), refill until it weeps from the fill hole, check the motor connector.
The shift motor (the #1 issue)
- The electric motor on the side of the case shifts 2HI/4HI/4LO. Its internal contacts corrode → no shift, blinking light.
- Test: unplug the motor, jump the pins per the FTE guide — if the case shifts, the motor is the problem.
- Fix: clean the contacts (there's a plastic cover over them) or replace the motor. Cheap and the standard fix.
- The 12-point manual-shift bolt on the case lets you shift it by hand in a pinch (never force it).
Service
- Fluid: 2.2 qt Mercon ATF, level plug on the case.
- While under there: check the front/rear driveshaft u-joints and the case mount bushings.
- If you hear a whine or the case 'pops' out of 4HI, it's internal — but that's rare on a 1356.
Related
- Front axle not engaging? See 4x4, hubs & TTB — the hubs are the other half of the no-4WD story.
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Threads
- FTE search: bw1356 · shift motor · transfer case