R6cowboy

5th and reverse problem in '00 C5 with T56.
Recently noticed 5th gear grinds on the 4-5 shift only when shifting very quickly at high rpm / topping out 4th. But it shifts perfectly smooth under normal driving conditions. Was told that the reverse lights also are turning on when this 5th gear grinding issue occurs. What could be possible issues?
Also, as soon as this 5th gear issue started, the trans started grinding sometimes while shifting into reverse at a complete stop. Sometimes it will shift into reverse just fine, but most of the times grinds. If parked on a slight incline and I shift into reverse during an ever slight roll, it will shift into reverse just fine. It will also pop out of reverse as soon as the car starts moving when backing up.

Are these two problems likely related? Or is it more likely that there could be a couple different problems occurring as once? I did some researching and it seems the 4-5 shift grinding is likely a faulty reverse lockout solenoid..?? But could that also cause the reverse grinding issue?

Thanks for any help!

SS2001SS

Reverse lockout solenoid is failing allowing the shifter to move into the reverse gate when shifting into 5th. Mine did the same thing till I replaced the solenoid.