cruiser54

See if your clutch pedal has a broken weld up at the top.

PatHenry

That's so strange - it almost seems like the disc is too tight on the input shaft when the metals expand.

I'd check the fluid level and quality as well, just to be sure. I would have suggested overheating hydraulic fluid, as that would make the pedal ineffective, but that would also make the pedal softer, not harder.

Cruiser's more than likely correct about the weld - he has seen a Jeep or two over the years...

Edit - On a side note, I have to laugh at how some people clearly don't read the posts. A poster a few years back mentions having put a new master/slave in and the Jeep ran great at first, then started having problems "as if there was air in the system".. literally 2 posts prior the O.P. described how he had to pull the slave and pump it a few times on his --- dun da da da --- new master/slave assembly to -- wait for it -- dispel a bit of air that was in the system despite it being "pre-bled". Wow.

Also, in case anyone was wondering -
AX15 89-93 - Internal slave cylinder (remove transmission to access)
AX15 94-99 - External slave (bolted to drivers side bell-housing)
NV3550 00-01 - External slave (same)