Hello everyone and thanks in advance for any help, This is my third Subaru, but I've never had this problem before.
A little history about the car: I bought it as a project, the PO had rear ended someone at slow speed (parking lot) and the trailer hitch (large truck) went into the grill, damaging the grill, hood radiator and core support. I have replaced the parts and have it back in shape. According to the PO the car had no problems before the wreck. It has just over 200k miles and lots of service records including a new (rebuilt I think) transmission installed about 60,000 miles ago, and a transmission fluid change about 600 miles ago.
Now the problem: I drove the car home about 4 miles and it runs and drives great, you would have no idea anything was wrong other than the noise. It shifts just fine into all gears, there is no slipping at all, I've checked all the wheel bearings and axles for play, and they all seem great. But any time I'm in gear and giving it gas, it makes a horrible grinding noise, it sounds like someone dragging something through gravel, similar noise to what a rock stuck in a break rotor would sound like.
What I've discovered: It doesn't seem to do it in Reverse, if you're driving and put the clutch in, it goes away, the more gas you give it the louder it gets, it seems to be based more on engine RPM's rather than speed, it's not totally steady - it seems to pulsate - and if you leave your hand on the shifter you can feel the pulsate. I am also able to recreate the noise without the car moving, by having the engine running and transmission in N, then without applying the clutch, try to push it into 4th gear, it obviously won't go into gear but the harder I push the louder the noise gets, and once I let off I can still faintly hear the noise for a few minutes but only about once a second (as often as it pulsates normally)
So I'm thinking it's clutch related, but maybe not? I would assume if it was it would show other signs like slipping, I've had many clutches wear out but they never made a noise. Also is it possible that the collision could have caused this? Sorry for being so long winded, I just want to explain as best I can.