after all that i take it my diff lock is knackered,i can turn tight circle with diff lock engaged no problem,as i was intending joining local off road club will lack of diff lock be a serious disadvantage. Jim.
Only if you want to run the motor off the jack.
Try jacking one side up so that one wheel on each axle can spin and you're in with a chance. Dont rev it up though just let it idle and be ready to kill the engine just in case you've got locking diffs. You should see both wheels turning if your diff lock is working properly.
Correct and safest way to do it is to get all four wheels off the ground with the vehicle sat on axle stands.