I own a manual 03 Xterra. For the past month whenever I try to shift into third gear it grinds and creates that grinding noise when you try to shift when the clutch isn’t all the way in. This grinding occurs a lot and doesn’t when I am going really slow trying to shift into third gear.
Any ideas on what could be wrong?
thanks in advance.
I would say that your 3rd gear synchro is toast. 
I am not familiar with the term synchro. How do I fix it, prevent it from happening again and how much is this going to cost are my next questions.
Thanks for your response.
Sorry, I was a little side-tracked when I wrote that, I intended to elaborate.
In order to match the input and output speeds of the transmission (the engine side and the wheel side), it makes use of friction cones which slide together as you’re making the shift. Synchronizing the input and output allows the teeth of the gears to mesh while they’re spinning at the same speed, and eliminates the grinding you’d get if they were spinning at different speeds.
Usually high-mileage is what results in synchronizer failure, simply because they can’t last forever. Are you the only one who drives this car? The best ways to kill a synchro are to skip gears on a downshift before the vehicle’s speed has dropped much (say, you’re bombing along at 75, put in the clutch, and shift to 3rd.) Shifting without the clutch (or at least trying) will do it too.
Fixing it… that’s going to mean the transmission comes out, gets opened, and a new synchro ring is pressed in place. I know some shops want to do an entire rebuild rather than just replace 1 synchro, so you’ll have to call around.
There is the off-chance that your shift linkage is mis-adjusted or bent, and you should have a shop check that out before you make any other moves. Take it to a reputable shop (preferably one that specializes in drivetrain work, if you can find one) and let them diagnose it, of course, but I’m pretty sure they’re going to say synchronizer.
Thanks for the info. I understand now what is happening. My wife and I drive this car and I can remember a few times of down shifting into the wrong gear but nothing major.
How much should I expect to pay for this and how much money is too much to pay for this?
It could cost you a couple thousand to get this fixed. Find a good transmission shop. DON’T go to the dealer. They’ll just try to sell you a NEW transmission.
In addition to what Josh said, I would add that one of the OP’s statements might give a hint as to the source of the problem:
“and creates that grinding noise when you try to shift when the clutch isn’t all the way in”
After having the synchro replaced, I would suggest that you only shift gears with the clutch fully disengaged (translation–all the way in).
That was a mistake on my part. The clutch is fully engaged when I try to shift and it still grinds. I just was trying to give an example of what the grinding noise sounds like (not inferring that I know how it sounds because I shift that way).
A couple thousand dollars to get the synchro replaced! It sounds pretty simple…not like a couple thousand dollars worth of work, but what do I know.
So how long do you think I can drive it until it falls apart! haha jk