Well it may be that ford(and it is true) ain't very serous about 4x4 in the ranger model. Some times it is cought in a bind and you might have to drive a ways or have to get lockers, that might solve our problem , try puttin it in 4x4 and backin up it releaves tention on the it back up like 25 yards or so I got down on my knees and turned the 4x4 drive shaft and I was never so happy to get my arm covered in mud fron the front wheels as I put my elbow out. It works like 70% of the time.

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99 ford ranger
4x4 30/9.50/15(soon to be 33/11.50/15)
red step side
stock lift
2 12" obcons
Sony xplod deck
4.0 v6