when changing into 2nd gear it either slightly crunches or takes a bit to get it into gear. what can i do to the gearbox to improve the gear changes.

put a new 2nd gear synchro in or change your oil to ATF

First, the no-cost check. Make sure the clutch is correctly adjusted:

- play at the pedal
- play at the clutch arm under the car
- No thick carpeting under the pedal
[edit] See the tune-up article for the clutch adjustment specifications

If you have more than an inch of play at the pedal, you won't be able to engage the clutch all the way. Hence gear-shift problems. If you have no play underneath, the clutch will slip.

For some reason, Datsun gearboxes that have seen some [ab]use seem to be a little slow into second. Particularly when cold. My original 1000 was like it, the 5 speed in my '84 Bluebird, along with the 5 speed GX box in my 1000 were like it, & the '82 Bluebird TRX five speed in my 200B is still like it.

The fix? After following ddgonzals suggestions, try taking it a little more gently into second, & let it warm right up before pushing it.

Can't do this? Then a strip & overhaul would be the task of last resort, as the second gear synchro has possibly worn to the point of being out of service limits.

Here is another tip,try double clutching this will help to align the speed of the two gears.
I would also as stated change the gear oil to ATF and add something like slick 50.

One other thing to look out for is the clutch pedal itself. On a road trip we did in a real basket case 1200 coupe some years ago, it got real crunchy to shift so we stayed in top.
What it turned out to be was the clutch pedal had bent over and was touching the floor long before it disingaged. I know this isnt your problem, but I thought it worth a mention anyways.

my sunny does that when it is cold, i didnt do anything to it, just get the hang of it and be careful, i have worked out a technique doesnt do it to me anymore but anyone else drives they cant get it right.

P.S cant explain what i do, i just worked it out one morning.