I keep having to add clutch fluid, the clutch is not burning and my truck is not leaking fluid. What causes this?

 

Suggest that you certainly have a leak somewhere.

IIRC the slave cylinder is integral to the throw-out bearing and may be difficult to see if the bell housing seals up tight.

 

If the slave is leaking, you will see fluid dripping out of the bottom of the bell housing. If the master is leaking, your carpet will be getting wet. Stick your head up behind the dash and pull the carpet back behind the clutch pedal, you will see it if it's wet back there.

 

I already changed my master cylinder and its not leaking. My floor is not wet neither I do not have carpet I have the rubber floor so it will be more noticeable. Just didnt want to mess with the slave cylinder. Thanks for the responses.

 

The slave cylinder has a rubber boot that can trap quite a bit of fluid before it shows a leak.

JMC

 

There is a rubber sight plug on the drivers side of the trans. Pull it off and have someone depress the clutch while you look at it. Look and listen for swishing noises and or a wet boot. Sounds like a slave cylinder to me.