clutch slipping

It's a manual trans, right?

Over 90k miles or tow a trailer? If so its the clutch disc --- assuming the clutch master cylinder had flhid in it. If its empty then slave or master cylinder could be gone --- but they affect engagement mainly.

An "Old Timers" way to check the clutch is to gently pull up to, and nudge, a big tree. Then put your tranny in 3rd gear, rev up the engine a bit and let out the clutch pedal. It should kill the engine muy pronto. If it takes a while then you have a worn clutch disc or a defunct pressure plate, or both. Gears do not slip, clutches do!

-- Jarhead

No. If the clutch is slipping on a 12-year old truck, odds are good that you need a new clutch.

no.

your clutch is done. have it changed or change it and replace:

- pilot bearing

- throwout bearing

- crank seal trans input seal

if the oil pan leaks it can also be tackled now

Matt

The mileage doesn't matter, I've seen OEM clutches last over 150,000 miles and some fail after 30,000. It's a matter of how their driven. The original post said nothing about engagement, just slippage when already in gear.