Gearbox advice

I have a 300 tdi which i use for launching a boat on a beach. Got in problems on the sand yesterday and tried to use low range. the box had trouble engaging and would not stay on low range even with me holding the lever. this is on an auto box diff lock is ok just keeps jumping out of low range any ideas of fix.

sounds like u didnt get it in properly, they do jump out if not fully in. Its better if u can try to put it into Low with the car slightly moving, as it meshes better. Procedure should be Gearbox into N, Push it into Low and you should really feel it mesh and back into D or whatever. If it still jumps out and your sure it was definately in, there might be a Linkage problem which isnt letting it get in properly.

Try it rolling (in N) at say 2-5mph and dont be afraid to give it a good push.

Hope this helps