Wrx 00 third gear make a grinding sound the more I speed the more the sound only third gear??

SOURCE: SLIPPING IN AND OUT OF THIRD GEAR ON A AUTO SUBARU WRX 95

It could be the clutch cable needing adjustment although this would be the ideal scenario!
More likely that the gearbox is worn to excess (a polite way of saying it is shot!).
I'm afraid to say I would favour the latter!!!!
I could be wrong though but I have seen this before and I feel your pain!!!!!

SOURCE: Grinds sometimes going into third gear

Check the fluid in your transmission. Check the level, as well as discoloration, or any particals in it.

Derek Bannister

• 101 Answers
• Posted on Jun 09, 2009

SOURCE: when i shift into third the gears grind.. why?

sounds like the syncromesh has gone in the gearbox. If you dont want them to grind, you,ll have to double declutch. I f you cant do this, get a new gearbox.

SOURCE: got subaru impreza wrx turbo 1993 , fith gear

Time to look around in junkyards or ebay for a similar transmission with much lower mileage, or google around and see if you can exchange that tranny for a rebuilt one.