Can you put Automatic Transmission Fluid or engine oil into a manual transmission?

[leon200608]

It may seem to be a stupid question, but I'm just curious. As everyone knows for auto trannies the ATF has a pink/reddish color, but all manual trannies fluid I've seen have the same color as the engine oil, maybe they do use engine oil in manual trannies?! Or they have some special fluid just for themselves?

Another question: does manual tranny fluid ever need to be changed?

[notanexpert]

Yes, manual transmission fluid should be changed. The synchros put tiny bits of brass shavings into the fluid as they wear, not a big deal but over a long time and lots of mileage they will cause increased wear on other components.
You never put engine oil into the transmission.
Most manual transmissions either use ATF or gear oil, usually 80W90 weight. You HAVE to check the manual for the car to know which to use. These oils are formulated very much differently from engine oil.
If your manual has no indcated service interval for replacing the manual transmission fluid, then I'd use 100k as the interval.

[leon200608]

Yes, manual transmission fluid should be changed. The synchros put tiny bits of brass shavings into the fluid as they wear, not a big deal but over a long time and lots of mileage they will cause increased wear on other components.
You never put engine oil into the transmission.
Most manual transmissions either use ATF or gear oil, usually 80W90 weight. You HAVE to check the manual for the car to know which to use. These oils are formulated very much differently from engine oil.
If your manual has no indcated service interval for replacing the manual transmission fluid, then I'd use 100k as the interval.

Thanks. By the way, for ATF in auto trannies, how often do you change them? Someone say change it once it turns brownish, some say change every 40000~50000km...

[notanexpert]

Thanks. By the way, for ATF in auto trannies, how often do you change them? Someone say change it once it turns brownish, some say change every 40000~50000km...

All cars are different, and they each have a recommended interval in the owner's manual. If you wait until the fluid is brownish... you're risking that you will not only need new fluid but also a new tranny.
Some cars come with "lifetime fluid" in their auto transmissions. What they fail to mention is that its "lifetime of the transmission", not "lifetime of the car".

[movieman]

You never put engine oil into the transmission.

Actually, one of my Italian cars (forget whether it was Fiat or Lancia) used engine oil in the transmission; using gearbox oil could cause premature failure. Also, didn't the original Mini use the same oil for engine and gearbox?

But, I agree, it's a rarity; most of my cars have used gearbox-specific oil.

[rchong]

Some manual transmissions use atf, some use motor oil, and some use gear oil. Check your owners manual for a recommended change interval. If applicable, make sure you can remove the fill bolt before draining the transmission fluid.

[notanexpert]

Actually, one of my Italian cars (forget whether it was Fiat or Lancia) used engine oil in the transmission; using gearbox oil could cause premature failure. Also, didn't the original Mini use the same oil for engine and gearbox?

But, I agree, it's a rarity; most of my cars have used gearbox-specific oil.

Ok, I stand corrected, however I don't think any modern cars use engine oil in the tranny. Most motorcycles have the gearbox and engine combined, so it uses the same oil, but they use special motorcycle oil, which is designed to lubricate both engine and gearbox.

[ES_Revenge]

Some manual transmissions use atf, some use motor oil, and some use gear oil. Check your owners manual for a recommended change interval. If applicable, make sure you can remove the fill bolt before draining the transmission fluid.

Exactly. And even auto trannies use different fluids as there are different types-- Chrysler, Ford/GM (where the fluid is usually the same), Honda, etc. all use different fluid for their auto transmissions. And it can vary by model within the same manufacturer.

Therefore use what's recommended in your owner's manual, for any car, for any transmission. Don't go putting the wrong fluid in blindly as there may be dire consequences.

[movieman]

Ok, I stand corrected, however I don't think any modern cars use engine oil in the tranny.

True; I don't know of any that have been sold new since 1990.