Just had problems with dhse 2.5 gearbox long change up to 3500rpm to change to 2nd gear so changed oil first then ran it for 50 miles still not changing up then 2nd oil change with pan filter changed drove another 50 miles got a bit better to change gear then 3rd time changed oil flushed it threw and drove 30 miles and absolutely perfect change up smooth gear change and better on fuel to problem solved