Gear shift delay and fault only develops when main beam is on
 

Hello,
just joined this forum and hoping to get some out.
Mr range rover sport 2006 2.7 has developed a fault ...the gear wont until it its about 4500 revs abd problem only occurs during night drivibg when i use the main beam.
if i switch them off the car droves fine.
to date the following has been done
1.transmission case module changed
2..New battery
3.brake light switch changed
4.multiple diagnostics
5.Alternator tested

I read that this problem could be related to ground wire which I will be lookinglooking just wanted to know if anyone else has come across this issue and share there experience..most impottantly what was the fix?

Thanks

Probably Best to post on the Range Rover Sport forum and not the Land Rover Discovery Sport forum.