Changed slave cylinder 92gmc 1500 have no pedal

Hi: Your slave cylinder works like the master cylinder, it has a resevior for fluid and needs to be bleed free from air.

If you're not planning to remove the slave cylinder, I found it easier to use a set of ramps under the front wheels and work under the vehicle rather than jacking it up and taking off the front wheels. Put one end of the plastic tubing on the end of the nipple, the other in the empty jar.
When you have reassembled the clutch hydraulics, refill the clutch fluid reservoir, make sure the bleed nipple on the slave cylinder is tightly closed. Now, with the piece of wood within reach, slowly depress the clutch pedal with your hand and hold it down while you prop the wood against it, wedging the other end against the bolt that holds down the left front of the driver’s seat. Next, open the bleed nipple on the slave cylinder. You may see some fluid, or just a puff of air, or perhaps some of both in the form of bubbles. In any event, close the nipple tightly again. On your way back to the clutch pedal, check the fluid reservoir and top off as necessary. Hold the clutch pedal down with your hand as you remove the wood brace, then slowly release the pedal. When it is all the way up, press it down again slowly and reinsert the wood. Open and close the bleed nipple again. Repeat the entire process as many times as needed until you see a solid stream of clear brake fluid coming from the nipple with no air bubbles. Be sure to close the nipple tightly each time to avoid sucking air back into the system when you release the clutch pedal. And don’t forget to check the fluid reservoir each time.
Check the clutch pedal with your foot to see if you have normal pressure. If it seems okay start the vehicle and put it in gear (reverse if you’ve got it up on ramps). Now take it around the block and roadtest it. If all is not right, you’ve still got air in the system and will have to bleed it some more. Re-check the fluid reservoir again after a few hours—you may find that you need to top off the reservoir one last time.
Note: When I did mine, I had let the system drain so I could flush out dirty fluid. The first couple of times I opened the bleed nipple, therefore, I pumped the clutch pedal three times in order to make the process go a little faster, because I knew that the first couple of times all I’d be doing was compressing air.
I have replaced both my master and slave cylinders and have found through this experience that you do not need to open and close the bleed nipple. Because of the location of the slave cylinder gravity does the job. Just loosen the slave nipple and let the fluid run out until there is no more air. You might have to pump once or twice but once the fluid starts to move it works on its own. Tighten, nipple and you're done.

Sounds like you have air in your line.bleed it.