Hi swoop and mr fixit
Arrived site on site removed the linkage from the top of the box and found that the block had jammed between the two actuator plates under the dash,freed it off truck is running fine now, but I think it was caused by partly, a heavy handed operator And worn linkage so I have advised the customer to replace the linkage as a precaution and I have a happy customer. Many thanks again for your input.
Cheers Ade