5-Speed transmission;Won't shift into gear. - 1992 Daihatsu Rocky

Probably the speed sensor on the transmission. It would cause both problems. You should also have a check engine light with a trouble code for the sensor.

Check speed sensor at transmission.

are there any codes? Does it shift ok in 1st and 2nd? sounds like your over drive shift solenoid or your 3 and 4 shift solenoid is stuck and needs to be replaced

may be you need a Odometer Correction Tools

Bad valves or possible bad speed sensor.

HI,
Search online..but it sounds like the 'synchros' in the transmission are going/gone.
Also, the clutch may be wearing out.

Td

A clutch problem will not interfere with gear selection when the engine is off and the car stationary.

It does seem like you have a gearbox or gear linkage trouble.

Assuming the pickup is an automatic, check the transmission fluid. The #1 cause for transmission slippage is lack of Automatic Transmission Fluid.

If the pickup is a standard shift, the pin that connects the shift to the transmission has likely broken. You would still be able to shift from the inside but the gears won't engage. A bad clutch is also a possibility but you would have noticed a burning smell prior to the clutch giving out.

Fourth gear in your vehicle doesn't exist. What feels like a fourth gear is the torque converter locking up. The lockup lockup is controlled by a solenoid in the side pan of the transmission, and the solenoid is controlled by the ECM (electronic control module) in response to several pressure, temperature and speed sensors etc. To determine which component is the problem you'll need a professional transmission mechanic with the proper diagnostic equipment.

This is the speed in and speed out sensors on the transmission. I just had the same problem. The sensors are about 25 dollars and are easy to replace