I have a 2004 Audi A4 1.8t. I recently began to have trouble getting into reverse when the engine is running, i can get it sometimes but that requires alot of force. And when i turn off the engine i can easily get into reverse.
What can this be?
It could be that your clutch is not disconnecting drive fully, so the reverse gears are not able to mesh. The synchros on the forward gears are probably putting enough load on the drive to compensate for the problem, therefore you are not experiencing it in the forward gears.
Does the clutch bite very low down on the pedal when releasing?
Welcome to the site!
My gut says that the gear shift linkage is out of adjustment. On these cars there are cables between the gearbox and gear lever. From around page 22 onwards of this guide gives you an idea of how to perform the adjustment; https://cdn.shopify.com/s/files/1/2597/0906/files/sigmasixinstall.pdf?8650546362459632524
If adjusting the gear linkage doesn't solve the probem it may be that you have worn bushes in the gear linkage in which case installing a replacement bush kit and then performing the linkage adjustment once more ought to remedy the fault.