Probs with transfer box. Any help?

I hope someone can shed a little light on this for me. My diff lock warning light stopped working leading to me travelling at speed on road with the diff lock on.

Since then I have been getting vibrations at 55 - 60 mph and there was a bit of metallic squealing which has now stopped.

I have presumed prop shaft bearings, but on inspection all seem fine with no play.

I did try to fix the diff lock light to find nothing wrong with the switch or bulb. The light comes on depending how far down I screwed in the switch, but not when I engage diff lock.

When I shone a light down the switch hole nothing seems to move when moving diff lock on or off although I would have thought something should to trigger switch.

My question is this. Can I have damaged something in the transfer box or can the tansfer box break? What can happen from driving at speed with the diff lock on?

Any help gratefully received.

Ta, Thatcherman

Righto, following my earlier previous like most helpful answer to you and having now removed the nut from behind the wheel...

I would check the following in this order:

Does diff lock work (prop up the front on a coupla bricks or summat and make sure at least one wheel is off of the ground and see if putting the car in diff lock will push it CAREFULLY off this pedestal) - if it does, difflock is fine and the problem is with the electrics telling you it's on.*

If not...then as i suspect, diff lock is not engaging, which is most likely a problem with the linkage (if you have changed the electrics, and the switch is a physical switch ie if diff lock is on then so is the switch). The linkages are a bit notorious so that's where my money is. Diff lock itself is a fairly reliable and strong mechanism, just the gubbins to engage it is a bit iffy!

Recheck the propshaft bearings, making sure the handbrake is off (BUT THAT YER NOT ON A SLOPE!!!) - chock the wheels to make sure and ANY play in either the UJs or between the splines in either half of the prop will manifest as grinding or vibration at between 35 and about 55 (particularly under load - ie up hill). I suspect this is a different problem, which, as it happened at the same time as the other one, you are connecting - although driving on tarmac with diff on could have caused it possibly (the UJs are the weak point in the drive train)

Failing a problem in the diff linkage, it may be somehting internal within the tranny box but they are so strong i would be surprised. (if so, advice is out of my depth and you might be best off replacing the tranny with a 2nd hand one) although i would be MOST srprised if this is the problem!

The diff lock switch needs to be screwed in just the right amount else it will eiother always be on or never.

*Thinking laterally, i suppose the only other possibility is that diff lock is not DIS engaging, but you will also be able to check this with the Brick-test!

Good luck, we must do some laning soon else summat might come along which may make it tricky for a few years