Mine was similar , particularly on damp days . It eventually would not engage any gears at all . Dealer had it for two days , fitted nearly £5000.00 worth of parts , which did not cure it . Problem turned out to be a broken wire in the loom . Fitted a £5 connector , removed the £5 k. Worth of bits and it is still performing perfectly 2 years later .
The big problem with the diagnostic plug in method of fault finding is that a broken and intermittently connecting wire will send a false reading to the computer .
I have recently had a similar problem with a 45 series . The diagnostics were showing several problems requiring in excess of a £1000. Worth of parts which again turned out to be a chafed wire in the loom . Both trucks were about 6 years old at time of probs
John
December 2013