I have a fun problem with my 04 6 speed element. A couple of days ago I took the transmission out and added a 6th gear I got from eBay. After I put everything back together I was able to get the car into 4th gear one time before it started popping out. The problem is that I can get the car into all gears while the car is stationary but when it’s moving 4th gear grinds and 3rd gear pops out. All other gears including 6th work fine. I was wondering what could cause this issue or if anyone else had had it. Thanks