To change the gearbox oil in a manual transmission you will need 4 liters(4 quarts) for a 4-speed box and 5 liters(5 quarts) for a 5-speed box. they recommend API-4 75-90 in early 22r motors(pre 1990), and seem to recommend API-5 75-90 in later model Toyota pickups(1990+) not sure what the difference is, API-5 seems more heavy duty.
to change the motor oil:
That depends on the engine, and if the filter has also been changed (it should be every time) and the filter brand (marginally). Add in 4 quarts (3.8 L) to a 22RE. Turn on the engine and allow to run for 1 minute. Turn off. May need anywhere from 0.5 quarts to a bit more. Always buy 5 quarts (or liters) and a filter (fram ph3614 is what I use).
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What is specified in your owner's manual.
A transmission from a 1993 Toyota pickup will fit into a 1994 Toyota pickup. The Toyota transmission will not fit in to other makes and models of pickups.
Gear oil, Best place to get it is at WALMART.
21mm socket or wrench
there is a fill plug on the side of the transmission towards the top if its not there then you have to add it while you build it but it should be there
About 3.5 - 4 litres.
automatic has a dipstick on drivers side manual has a fill hole in the side
you dont have to but it makes it a lot easier.
it has an oil filter, fuel filter, air filter, but no trans filter.
there isn't one period
The manual transmission fluid capacity for a 1991 Toyota pickup is approximately 2.4 quarts (2.3 liters) when filled to the proper level. It's important to use the recommended gear oil, typically 75W-90, for optimal performance. Always consult the owner's manual for specific details and confirmation.