Rear O/S wheel locked up

[rborist]

Driving on the road, turning into a right hand junction at about 20-25mph the rear o/s wheel locked up for about 10 yards. I had the brakes checked right through and it's not that. Any suggestions as to what might be the problem.
1st and only time this has happened.
(98 4.0 V6 Auto)

 

[Crankcase]

I would check the oil level in your rear differential.