Cable adjusted properly? i.e. does it grind normally when shifting into reverse at a stand still?
If not I would be willing to venture that you are just above the RPM threshold that you should be below when shifting into reverse... If you look at a T5 transmission manual it states a source of grinding going into reverse as 1) bad cable adjustment 2) IDLE RPM too high - in your case the car moving will raise the RPM as you engage the clutch...
My TKO500 does this and my T5 did too. I would stop completely before putting it into reverse if I were you. Also I always push the clutch in, go into third gear, and then reverse.
Do you think a bad throwout bearing could cause this?? Also I think that automatic clutch adjuster that is supposed to work when you pull the pedal backwards is broken..it doesent just click anymore it like feels like its just like breaking when i pull it back..It goes way farther than its supposed to
It may be worth checking out how the cable is adjusted, but if it doesn't do it in the other gears I would see if it has to do with your speed first. Also make sure your clutch is full disengaged (pedal to the floor) before attempting to shift into gear. Mine has a heck of a time going into gear half of the time anyways, but it doesn't grind. If it doesn't turn out to be your speed reverse may be going out, but I don't believe that to be the case. If I remember correctly reverse isn't synchroed, someone with more transmission knowledge may be able to assist further.
Reverse has straight cut gears - it's not a synchromeshed gear. Even when stationary, it's customary to put the shifter in a forward gear before going into reverse - the engagement of the forward gear slows the cluster down to reverse can engage smoother.
clutch cable adjustment... When installing my tko-600 and mcleod clutch it said right on either the tranny or clutch instructions that reverse grindage was a way of telling if the clutch cable slack needed to be tightened up.