My bone stock 205 in my '79 F150 once went into front drive only. Never figured out how it did it.
I backed up along side my friend's house to make loading some fishing gear easier before daylight. Noticed the dirt seemed a little soft.
He came out and freaked slightly. Said I was in the wife's future flower bed that she had just gotten prepared.
I said don't worry, I'll ease out.
While he was loading the gear, I turned the front hubs. Figuring I would just roll out without any digging in. I had my summer tires on, which were 12.50/33s with almost street tread.
Cranked the truck off, just to make it nice and slow I shoved it into 4lo. Shifter felt a little strange going in. Despite being in low range, it did not start off in idle.
I touched the gas and it started digging down in front like a frightened gopher.
We got out, rear tires had never moved, front had dug in about 8 inches.
I got back in, slammed the shifter all the way back into 4hi and it rolled out of the holes without any digging.
When we hit the pavement, I put it in 2hi and we went fishing. Didn't even stop to unlock the hubs for several miles.
When he got home after dark, she was still mad. But, I had parked around front, and she did not see my tires, so no chance she would recognize the tread. She was complaining about some of the neighborhood kids driving through her garden last night, and we promised to keep an eye out for the culprit.
Not sure if he ever told her different.
Truck never did that again in the 10 years I owned it.