JD 6600 transmission

Hello all. I dont post much but this problem has got us stumped. I am posting for a friend of mine who owns a JD 6600 with the positorque drive transmission (non hydro). The problem is that it wont shift into 1st or 3rd gears very well. It will just grind. Now let me give you a little back story. A couple years ago it had a similar problem and after taking the transmission apart I found that the cam responsible for moving the shift collars into their respective gears would not move the collar far enough. I dont remember the nitty gritty details but I do remember adding a 5/16's washer somewhere to get it to move farther to catch 1st and 3rd but then it took away from 2nd and 4th gears. If I added any more it would not catch 2nd or 4th at all. The collars did not have much of any wear on them, it just seemed that from the factory it BARELY moves the collar to engage the splines. I guess what I am asking is has anyone seen this before and what did you do to solve the problem? It seems to me that the cam responsible for moving the collars is not machined properly where the rollers follow the track. The track should be machined so it moves it farther. Any insight to this would be appreciated, thanks guys!

Curt, know this is a little late for a reply, just (wasting?) time looking at older posts, I had one of the early 6600's (the model where it took super hot engine compartment air and blew it out thru the radiator) that had similar problem if I recall right. I corrected it by changing out the worn shift cables and adjusting them. It worked well "til she overheated and cracked the head.
Then I installed a fan off a 7720 which had a different pitch and sucked air into radiator from outside. anyhow, that is what I remember about the old beast. Still use a 6600, but it is one of the last two years models, does a great job on my 500 acres every year.

Dick