Boxster 986 Third Gear Grinding every time I shift into third.
 

Hi All,
I have a 99 boxster with 110,000 miles and a five speed transmission. Every time I shift from second to third, i get a some grinding. It was coming up intermittently last couple of days and now its happening every time i shift to third. Does not happen at any other gear. I can also feel the teeth grinding on the transmission shifter. The sound is pretty loud. Is this a bad synchro? I have also noticed on third gear, at 3k rpm precisely, i hear a small grinding sound for a millisecond. It does not happen at any other gear at 3k rpm.

Any one know what might be going on?
Thanks,
Vidhu

So, I've had this happen in another vehicle of mine. It ended up first being the transmission fluid that was used. It was breaking down too quickly and was causing a grind in 3rd and 5th gear. I changed the fluid to something a bit better and the grinding went away. Fast forward about 9 or so years later, I started to get a grind in 2 gears again. I knew it wasn't the fluid and was the synchro's this time around. Had them replaced and the grinding is gone. Not saying your issue is the fluid, but it may be a place to start. Knowing your mileage, this may not solve your issue though. Just some input from my experience, but hopefully others might chime in with additional input for you.

If you decide to tackle the fluid first, this might help you: Porsche Boxster Differential / Manual Transmission Fluid Change - 986 / 987 (1997-08) - Pelican Parts Technical Article

This happened to my 2000 Jeep Wrangler that I just sold a month ago. My issue was the gear box was starting to leak and needed to be replaced. The funny thing is that if I slowed down my shift, that is I let the shifter rest in neutral a second longer before advancing into 2nd or 3rd gear, I had no grinding sound at all. I would definitely take it somewhere and get it looked at though but you may want to try slowing your shifts a little to see if that will at least eliminate the noise in the meantime.

Not sure what you mean by hearing a "small grinding sound" at 3k rpm. Do you mean when you aren't shifting? The grind going in sounds like a synchro issue. You could try a fluid change but usually there isn't anything you can do short of replace or rebuild the trans. In the meantime, slowing down the shift will give the synchro more time to do it's job and reduce the grinding.