Hi just bought an 06 TL 6spd. Love the car so far, but tranny is a little worrying. 2 things:
1 - 3rd gear grinds sometimes trying to go in. Have read something about GM synchromesh fluid? What do I do with that?
2, and probably more serious: Intermittently (sometimes once on a drive, sometimes every 2nd time I stop) the clutch goes soft and refuses to release from gear (or sometimes go into gear...depending the situation). This notably happens when starting the vehicle in 1st... quite often it wont come out of gear. If I release the clutch and re-engage it fixes the problem. I checked the fluid level - seems fine. Is this master cylinder issue?
Thanks! Of course non-of this happened when the bastard was selling it to me last week :-(

 

Start by changing the tranny fluid using The GM Syncromesh Friction Modified. Make sure the words 'Friction Modified' are on the label. The GM stuff has been replaced with an AC Delco Part# 10-4014. Call the GM dealers in your area, starting with the Chevrolet ones since they're most likely to have it in stock.

Then take it from there ..........
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Just updating this post: Put the syncromesh fluid in and now 3rd feels like new... no grinding whatsoever.
Got the dealer to change the master clutch cylinder. It's probably 95% better than previously. It doesn't stick ever going in/out of gears like before. The clutch still changes if you go hard revving it... especially between 3-4 gear... it's like it engages/releases really close to the floor... not sure what that's about, but I can live with it. Hope the update might help someone with similar issues. -t

 

Don't forget the slave cylinder. Try pumping the pedal a few times before shifting to see if any difference.

 

You might try adjusting the clutch pedal height if there is any to get it off the floor.