rockwell t221 wont stay in 2wd -

[kernalklink]

any suggestions - i can force it down into 2wd and it pops back up into 4hi - i tightened the linkage and that made it less wobbly but it still pops back into 4-hi - the guy i got the truck from had bolted some small chain under one of the tranny housing bolts and just chained it down into 2wd and it works fine. but then its sucks when you have to go to 4wd - i have the motor out right now and open to any suggestions - ive never really had a 4wd truck before so haven't had alot of experience with transfer case operation.