Strange one

I have a ford focus 1.6tdci 2012.

I have changed the gear box t

As the original had bearing issues. Now the crude control will not work in 6th gear but it does work in 4th and 5th. 

Also I think the grain is different as the previous box had good acceleration in 5th and 6th but this one doesn't. 

Any suggestions welcome

 

Do you know what the box came from?  I assume it wasn't an identical car?

It sounds like the PCM is noticing the gear ratio is different to the original config.  You might be able to change that with FoCCCus or Forscan but would need to know the 'new' ratio.

@Wray109 Did you get this resolved? Having a similar bizarre issue on a Mondeo. Cruise is fine except for the top gear. (5th)

there is some magic on my older 57 plate 5 speed manual... it knows what gear its in.  Not sure how.???... after swapping the GEM, I realise this stupid car won't engage cruise in 2nd gear anymore (let alone the stupidity of the higher min set point and cancelling if you ask it to drop to 19mph, like it used too happily). I used to use where needed, for speed bump infested 20 mph zones

So for your car I guess somehow either a software update to match what it needs, or a configuration change is required to tell it about 6th ???

Gear choice is simple maths, it just compares the RPM (crank sensor) with the road speed (ABS sensor) to work out the gear ratio. 

I'm still unsure whether it can be altered in Forscan to accept a different 'box though.