Diff Lock question - 110

During the snowy spell in January, I ended up towing a few stuck cars that had slid off the road.

One day I towed a long wheelbase transit van up a 1/7 hill.
The hill was covered in sheet ice, that you struggled to stand up on let alone anything else.

I reversed down to the stuck transit van and attached the tow rope.
Put my 110 in low range first with diff-lock engaged.

As I let out the clutch etc to move forward, my 110 started sliding backwards, even though the wheels were turning slowly forwards.

At this point I about shat me self , thinking I've dropped one here, and will end up sliding into the van I was trying to help. I tried this a couple of times with same end result - sliding back, even though wheels were turning forwards and slowly at that.

So in an act of desparation I took diff lock off, and left it in low range 1st only with no diff lock.

This time 110 went up the hill fine, towing the van with no probs.

My question is then - what was I doing wrong ?
I have pondered over this for a while. I thought putting the diff lock on would have helped traction, but in the end I got better traction with it off rather than on.

yep. sounds wrong to me too.

How do you know the wheels were turning forward?

Sounds like when you selected low/diff, the transfer box was actually in neutral. as you came off (hand)brake and clutch to move up the hill you began to roll backwards. By selecting low/no diff, you re-engaged the gearbox and were able to pull away...

However, if your wheels were definately turning whilst in low/diff, then I've no idea!!

Could be Mikes right.
I know finding low can be a bit tricky sometimes...

careful setting of splined part of linkage and linkage can improve it.
Also see if rubber boot causing issues

Mike_B said:

Sounds like when you selected low/diff, the transfer box was actually in neutral. as you came off (hand)brake and clutch to move up the hill you began to roll backwards. By selecting low/no diff, you re-engaged the gearbox and were able to pull away...

Click to expand...

This may have been the case thinking about it.
Cheers for suggestions.