Both rear diff locks??? That's a new one Old Fox. Do you mean front, centre and rear? There are only three. One in each axle and one in the centre transfer box.
THB squirting WD40 down the breather really isn't the cure here. Unusual for them to lock and then fail so they won't unlock. But, not completely unheard of. Especially for all three to lock up. I suspect that they have somehow wound up the drive shafts sufficiently to have locked the mechanisms. You don't get much wind up in an 80 because they are so well designed, but if they've been fiddling. Best thing really is to jack the truck off its wheels. All four would be best but at least one front and one rear. Then wiggle the wheels and it should unlock. Now someone will say drive back and forth and turn the wheel and ordinarily I'd agree but we don't know just how wound up they have got this so I'd suggest in the interest of not breaking something, lift the wheels. Also put the high / low transfer lever into neutral
That would be my first attempt. Make sure the rotary dial etc is turned off - obviously
and have just repeated what the youngun told me. I'll go to the garage myself in the morning and put it on their 2 post lift and try what you suggest with all 4 wheels in the air.
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