I wasn t using it and left it parked for nearly a month, then i needed it for some errands and it worked fine for the first run (maybe 5 minutes drive) then i parked it and after a few minutes i went out again and when i reached 4th gear it started vibrating a lot till i got back home it strated vibrating from second on.

When i say vibrationg it feels like you have a puncture and there is no punctures. I didn t use the 4x4 so it s not stuck.

the land rover is a 1977 series 2 with a 2.5l rover engine and 4 speed box

any suggestions where i shall have a look first?

 

Crawl under and check your rear driveshaft u-joints. That's where I would start.

 

Yup check those ujoints. If it has been a while since replacing them I would just put new ones in. They are like 7bucks each. Also check the yokes for movement. If it's not there pull the third member and check the spider gears for movement.

 

Things rust when not being used, including u-joints.

 

well i tried it again this morning and the front prop shaft cane undone from the differential side.

what i found strange was that the rear part of the shaft kept on turning untill i changed to low and back to high a few times.

 

Your u-joint broke, that was the vibration.
The prop shaft kept turning because it was under power and with no resistance it turns super easy.

 

now it stopped turning and the u joints didn t break the nuts just came undone from the diff side. the u joints don t have play as i check them regularly and grease them every month or so