"Yes, it's not that hard, just a little fiddly with the balls and rods. But the second gear problem could also be a broken top hat bearing, which requires the main shaft to come out to fix. Try the detent first, and if that doesn't work, then the top hat is the problem a problem of the detent ball or the spring being worn." I'm running a TR6 box in my 3. I read one article about this that shows some kind of a spring tensioning tool to test the spring rate with. Apparently there has been some changes in the springs thru the gearbox range. I was hoping to just order new TR6 springs and install them but I'm not even sure the top cover is from a TR6? Were the top covers interchangeable? The TR6 gearbox is synchromesh for 1st gear....would that change the spring rate?