So I replaced my clutch master and slave in October because my master gave out so I replaced both with new aisin parts. I believe I bled them correctly but I've noticed when I drive and put it in reverse it grinds. Last week I drove the truck for about 20 min and it would grind horrible going in reverse to the point that I was scared to try and put it in reverse. I've bled the slave twice again and air came out it felt smooth and easy to go into reverse. Today I drove for about an hour and when I got home it put it into reverse and it would grind again. I'm almost 100% sure that if I go to bleed the system tomorrow it will have air. Do you guys have any idea what it might be. 86 4runner 22re