bearing preload

[240b]

Iam replacing the thrust bearing  between the input shaft and main shaft in a Eaton mid-range gear box (4 speed). Would anyone know the "preload"on the bearing? It is adjusted with a shim pack on the rear of the case. 

[mad murdock]

Generally if it is a tapered roller bearing, you can tighten it down to the point where it has a little friction, but when rotated, you can not feel the individual rollers.  You need to check it for proper set up with the bearing lubed.  Do not set it up dry.  You also need to get a read on the rotational load or friction, AFTER you initially begin to move the bearing, break-away force is not what you are checking.  It can be real specific to the application, repair manual specs should be followed wherever possible.  Most mid-sized tapered roller bearing preloads that I have dealt with in various drive trains on various types of equipment I have experience with (truck, heavy equip. to helicopters), range from 4 in. oz of rotational drag, to as much as 16-18 in. oz.  This is measured from the center of rotation, so you usually need to calculate from the point (tangenial distance from center) at which you are measuring the drag.  We use dental floss or wax string, and a fish scale to check this on our overhauls.  Again, if you have a manual, or if someone on the FF has access to the specs from the manual, That is the info you need to use, to be sure you don't eat up new parts by not having the set up correct.