i have a 1988 upper the gear set went on it ,i got a used newer gear set i put it back together with the old parts and when i put in the upper it will lock up when i will lock down no the bolts to the top cover ,i got the updated shims and it still lock up. is it the shaft is not the same on the new gear set or some other part from the old part that does not work with the new gears set? thanks mike

Mike,
by new gear set do you mean the thick floored gears, referred to as X gears? Did the new gears come with thicker thrust bearings that go below and above the driven gears? If they are the new style.. then you need to change out the cone clutch. The shift fork is different for the new gears as well as the bearings under the springs in the gears are different also.
So if the needles in the thrust bearings are .125" ver .078", then you have the new gears.. You will need shims that are in the .050" range.. They make three sizes that corresponds to the number stamped on the back of your upper housing. Just subtract .040" from that number and it will give you the close to correct shim thickness.

Hope this helps.

i have to change the cone clutch and the shift fork,the shift fork do i change all of it or just the part that goes to the cone clutch.the bearing to the cone clutch how do i know that i have the right ones,thanks mike

You need to know the thickness of the thrust bearings. Also if you look up the part number that is on the gears you will be able to tell if they are the new style or the old. The old are no longer available.