I'm normally trying to stay at a constant 60mph, the RPM is around 2,000-2,100 in 5th which I believe is why it's not changing up into 6th, if i give it a bit more throttle to take the RPM to around 2.2k then it will go up to 6th, thats why i just upshift it myself, at which point the RPM is around 1.7k in 6th gear