2006 GMC Canyon manuel transmission. When the clutch is fully engaged, there is a high pitch grinding noise. It is also hard to get into gear. What could this be?

With the engine running and the clutch pressed all the way down try each gear in turn and listen. Do you get any crunching or grinding noises? Nasty noises on gear changes with the clutch fully pressed is commonly a sign of a badly worn clutch. No noises suggests linkage problems or an issue inside the transmission itself.
On a manual transmission you start at the gear stick and work down to the actual transmission. First check the links on the gearstick under the floor. Then follow those cables down to the transmission and check the linkages at that end. Sometimes a worn or loose linkage bush can cause loss of gears. Next check the arms and levers on the outside of the transmission itself. Work it by hand feeling and listening for it "Clunking" as it drops into all the gears. If it doesnt feel solid and 'notchy' the issue could be inside the transmission itself. You'll need a gearbox specialist to look at it for that issue.

this manual transmission?
seems. so
the tip of shift levers love to get worn and not allowing the shift rail forks to hit 3rd gear.
a pure simple mechanical failure and is shifter tip end parts bad, some are even made of plastic.
or
3rd gear synchro- ring is super worn out and the main clutch drags. (seen it and fixed them)
if clutch has master cylinder is the fluid always at top line or drops in time every weak.

It could obviously be the tranny is gone, but you would want to make sure you have enough clutch flood and the clutch is fully engaging. I had a leak in my 98 cavalier clutch fluid, and when it got low, it would not fully engage the clutch, simply making it hard to get into gear. Its DOT3 fluid. If so try reversing a little bit and gently tiring to get into gear. I believe 1st and 2nd gear share the same gear selection fork inside the tranny. Drain fluid and look for metal.

that sounds like a throw out bearing failure-is there any adjustment at the slave cylinder-it may be holding the bearing against the clutch and causing the noise-this thread may help-http://www.jeepforum.com/forum/f9/how-change-bleed-clutch-slave-cylinder-511531/- cheers Denny

Go with the related help links,to replace the clutch assembly:----Click the link below:---

2004 Peugoet: Clutch not going in gears?
http://whoisbyme.blogspot.in/2012/05/peugeot-307-clutch-will-no-go-in-gears.html
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Manual Transmission Clutch System Failures?

http://repairhelpcenter.blogspot.com/2011/11/manual-transmission-clutch-system.html

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Car makes noise when clutch is pressed gently? http://schematicsdiagram.blogspot.com/2011/12/car-makes-noise-when-clutch-is-pressed.html

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How does Clutch works in car?

http://vwrepairhelp.blogspot.com/2011/11/how-does-clutch-works-in-car.html

Clutch pedal hard? http://schematicsdiagram.blogspot.in/2012/02/clutch-pedal-hard.html

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2001 Toyota Celica: Grinding noise when Clutch pedal is Pushed? http://howtobyme.blogspot.in/2012/05/2001-toyota-celica-grinding-noise-when.html Toyota Celica Noisy Clutch? http://howtobyme.blogspot.in/2012/05/toyota-celica-noisy-clutch.html

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No Clutch Pedal No pressure http://whatisbyme.blogspot.in/2012/07/no-clutch-pedal-no-pressure.html 2006 Cadillac cts-v Clutch Getting stuck? http://schematicsdiagram.blogspot.in/2012/04/2006-caddiliac-cts-v-clutch-getting.html

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you need to replce the cluch and preasure plate. the clutch is gone, its hard to shift because there is nothing left to pushout on the plate and the squeeling is from the same problem, the clutch works like brakes, when the pads are gone and you step on brake you get asqeeling sound from it being metal to metal the same thing is happening with your clutch

Definitely not good. The transmission is slipping internally due to worn gears and clutch packs. It will have to come out for rebuilding, IMO. Have a transmission shop check it out.
Good luck.

If it feels like the clutch is slipping, chances are it is. If there was a problem in any component that has internal gears, you would have grinding noises. Gears cannot slip. As the clutch wears more you may hear grinding when you try to change gears but that is because the clutch won't fully disengage so the gears are spinning too fast to shift properly. Before that happens, have the clutch replaced.

It may be the transmission input shaft bushing or bearing, located in the rear of the engine crankshaft, in front of the clutch assembly. If the bushing or bearing is dry (needs to be greased), the input shaft will still try to turn with the engine rpm, even though the clutch pedal is depressed. Also, the clutch disc may not be fully releasing, which could possibly be corrected by adjusting the clutch pedal linkage. good luck

Sounds like a throw out bearing or pressure plate problem. Run it by a trany shop, and they should be able to tell quick and easily if that's the problem.