I have a problem with my mazda lantis '94. it seems to drive fine when i drive at 50km/h but it slips out of gear all the time. would it be the transmission itself or the sensor?
Is your vehicle automatic or manual? If its automatic start the engine and leave it idling. With the engine running check the gearbox oil level on the transmission dip stick (the one with the red top) and make sure that the fluid level is correct. If not, top up through the same tube where the dip stick fits. Don't over fill. If the fault persists the problem will be inside the gear box with the clutch and drive bands having most likely been damaged. The best and most economical way of fixing the vehicle will be to look for and get a good second hand box and have it fitted.
If its manual there is a probability that the syncro mesh cone has worn out. To repair the box is not very economically viable, so I'd recommend the same as for the auto box. Get a good second hand box and fir that.