05 tj clutch

Hello everyone
I have a 05:tj with 4.0 6 speed tranny...having clutch issues,clutch started slipping...so I bought a new Luk clutch kit,the old clutch that came out looked pretty,good,so,today my new clutch kit arrived and the disc seemed about the same thickness as the new one?but maybe the springs were a lot weaker on the old clutch,the old clutch was a Sachs looked it up and it was a pricey clutch kit when new 260.00 but back to the clutch issue,I installed the new Luk,kit almost have it all finished bolted up...I’m thinking I hope this is my problem?the master and slave clutch cylinders seem to look ok?but on the slave that bolts,to the bell housing the rod that sticks out..how do you get it to go back in far enough to bolt the cylinder back to the case?bleed it from the top?its very tight and I can not push it in far enough to bolt,it?im hoping I just didn’t just spend 150.00:for a new clutch imdidnt need?
Symptoms of,the old clutch,,,once motor got warm clutch would shift but slipped like crazy....