Here's a link I made with pictures and explaination for using the cih shaker centering tool.
http://talk.newagtalk.com/forums/thread-....7&highlight=cih
But that is for after you press in new bushings. Depending on your annual hours, if you've ran it 2 years and dont know if/when they were replaced by the previous owner, (assuming used machine) you might just consider a bushing kit this year.
Once you have some experience with worn out bushings, you will develope a "hunch" or "suspicion" about a bushing during the morning look over. Tell tale signs are a tear in the rubber, or a rubber that is bulging outward from the sleeve. Sometimes if the bushing adhesion to the metal sleeves has come loose completely, a grey color dust or ooze if you had water inside, will appear around the bushing.
If you do not wish to buy a bushing press die set, see if your dealer will loan or rent you one. It is worth the money, takes the doubt out of proper pressing technique. The dealer should loan you the centering tool. If you do not trust your skills, you might take all the arms to the dealer and have them do the press work, just visually inspect each bushing before you leave the dealer to insure there is no deformation of any sleeves or any sort of deep gouges in the sleeve.
Improper pressing technique can "mushroom" the outter sleeve or push the inner sleeve loose from the bushing. It can also gouge or deform the bushing if it is forced into the arm from an imperfect angle. A well respected IH owner and mechanic, Jon Hagen has said to use brake fluid as a lube for installing the new bushings as the brake fluid will not harm the rubber when you get some fluid on them during installation. Sounds great to me.
If you do the pressing yourself, see if the dealer will allow you to view the service manual for this procedure. There may be a chart that shows the approximate dimensions that should be achieved when the new bushings are installed.
If you miss finding a bushing that is out for some time, it will begin destroying the rest of the shaker system. Often it will start with breaking the tail of the chaffer rails where the chaffer is held up by a 3/8" bolt. Next stop may be the grain pan behind the bed augers. It will crack and disintegrate rapidly. Chaffers will break in half. Lots of bad things will go wrong right when you least can afford them to.
If you do the bushings, dont neglect going through the bearings and cams on the shaker drive. The whole thing should be inspected and worn parts replaced.
Dont know if that helped you any or not, but it's all I can do right now.