How can I tell if I have a bad 3rd gear synchro? The car shifts fine when I'm driving normally and every once and a while when I shift hard into 3rd, it will go in but I let off the clutch to give it gas it just revs up like it didn't even go into gear, what could this be?

 

This method use to call out any bad syncros...not sure if it works on the new fangled trannies but don't know why not....while idling carefully and slowly try to put the car in 3rd gear WITHOUT pressing in the clutch.....if it grinds away them you got a bad syncro. If you try that method on a good syncro it will not grind and you will notice a very slight decrease in idle speed due to the extra load.

 

Awesome I will have to give that a shot, this is my 2nd c6 vette now and this has happened in both cars now, when at the drag strip I would have to shift real slow into 3rd and lose some good time because of this

 

Dare to guess either a worn shifter band outer groove, or a worn out set of shifter fork tabs or levers.



Part 8/22 is the shifter fork tabs,


Outer band would be part #2 and the shifter fork tabs push against to shifter the ring band to move it back and forth in and out of gear. when the ring band gear is in the middle, gear not ingauged, and when it moved to either right or left of center, then it engauges that gear.




So short version, If you have been banging the trans sling-shot'g it into the gear, instead of letting it going into gear itself, then this cause the shifter fork tabs and the OD channel in the band ring to wear, and even to cause wear back at the shifter fork parts to wear out too.

So no grinding, the syncro itself sounds fine, but band gear is not being pushed all the way over to full engage via the shift fork instead.


In the below video, before you click on the link, the band ring on the left hand side bottom with OD channel on the output shaft , when pulled to the right via the shift fork, puts the trans into 3.

So right hand side band gear below, it pushed to the right instead of being in the center, puts the trans into 1, then when pushed all the way to left past is center postion, trans in 2. Far right hand band in the center so it not engaging 1 or 2, then the left hand band pushed to the right from it center position puts the tans into 3. When the far left had band is pushed pushed to the left past is center position, then the trans is in 4 (input and output shaft locked together. As for 5 and 6, that band is part of the intermediate shaft gears instead.


So to sum it up, the glitch you are having, the far left hand band is not being pushed far enough to the right to fully engage 3 gear, screaming a problem with the OD channel on the band gear, the shifter fork tab worn out, or the linkage back up in the shifter indexing not pushing the shifter fork far enough to the right instead.
So on the bright side, pretty cheap in parts to correctly, but no joy dropping the trans out and having to split it to get to the parts to begin with.

Do the repair yourself, and your into parts for around $150.
Have a shop do the repair, and your in the $3K range for the labor to not only first pull the trans and put it back in, but that fact that they need to warranty the trans for a give amount of time, and it will a full rebuild that they will do to the trans instead.