R380 bias spring adjustment

Hi.

Since I've owned my P38 I've had a difficult shift into the 4th gear. I've read that this can be solved by adjusting the bias spring on the box. Now, I've looked at the R380 service manual but there's no info on where this spring is located, for the type D box (which is installed to my P38). Can someone shed some light on where I can find the screws that hold this spring ? Is it a box out job ?

Regards,
Manuel

you haqvent got bias springs as in disco you have 2 sprung loaded adjuster screws can be bought from ashcrofts the fall to pieces common fault adjust with stick on so it allways falls into 3rd 4th alignment

Thanks for the quick reply. Can you tell me where are these screws located and what's the best option to adjust/replace them? Do I need the box off ?