ok i have a 97 te magna 5 speed manual and every time im in fourth gear it pops out of gear and back into neutral..it use to only pop out when i give a bit of revs or going up a hill in fourth but it seems to do it all the time now .. any help will do i live in south Brisbane so if yous know any1 around hea who can help that will be awsum

I might be completely wrong but could it be that you have broken mounts?
Does your shifter vibrate like crazy?

it vibrates a bit but not crazy

if all the bushes and linkages and stuff are sound, it would be the detents in the box itself i think

I know on the 2nd gens there are some big metal balls in the housing which keep the gears in there selected loactions as such
http://i21.photobucket.com/albums/b294/Mondoman9630/3000%20GT/Transmission/IMG00732-1.jpg
Chances are, as long as the 3rd gen GB uses the same principal, that's your problem.

if thats my problem would i be able to fix that or do i need a new gearbox ??

My girlfriend had that happen to her Pulsar for 5th gear. It was the syncro for that gear.. $$$$$$

Recommend you find a 2nd hand box :)