But maybe this can help - if a tooth goes on a diff planet gear you lose drive, so replace with a second hand diff
You need to find the actual problems, no point anyone just tossing in odd suggestions as to what might have broke. So I'd start where it broke first, at the rear.
First I'd check the rear prop and UJ's. Then take the drive caps off and half shafts out .. that'll determine if it's them. If all so far has been OK then you need to check the diff .. but frankly it does sound like the diff .... So maybe worth dropping it anyway.
Then do the same for the front .. but you've got the additional problems of CV jints and swivels etc to contend with.
Get yoself 3 or 4 half shaft gaskets and a couple of diff gaskets. Drain the oil. Remove the two halfshafts. Support the nose if the diff with a jack, remove the ring of nuts except the top one, which you leave loose. Wriggle the diff nose to break the seal. Careful use of a screwdriver might be needed to break the seal. Once lose, remive the last nut and CAREFULLY lower the diff. It is very heavy if it falls off the jack. Two peeps make it easier.
