I assume it's a cable operated clutch as other Nissans of that age were.
Can you detect free play at the top of the clutch pedal movement? If not
then it can cause slipping. You can adjust the cable on top of the gearbox
to get some free play in the foot pedal, about 1 or 2 cm is usual. If that
doesn't work you need a new clutch.
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.