Pilot bearing and bushings

 

<blockquote> "In most cases, this is a porous bronze, pre-lubed bushing rather than an actual bearing, as it is often called. A few applications still use an actual bearing and others use a needle roller type bearing, but by far, the most common type is bronze. You cannot use a roller bearing on a transmission shaft originally designed for a bronze bushing due to different type of heat treatment on the shafts.</blockquote>  

<blockquote> "Most people have no idea what an important part the pilot bushing plays in the life of the transmission and clutch. The job of the pilot bushing is to support the end of the transmission input (main drive) gear in the crankshaft and it only acts as a bushing when the clutch is depressed. This pilot bushing should be a light drive fit into the crank bore. Care should be taken when installing any pilot bushing as they are soft and easily damaged by crude installation techniques. A damaged pilot bushing can bind on the input gear giving symptoms of clutch drag. Transmission damage and early failure can be caused by a pilot bushing or crankshaft bore that "runs out" in relation to the transmission locating bore in the bellhousing. It is advisable to check the bore of the crank with a dial indicator before installing the pilot bushing. If the bore runs out more than 0.003" total, the crank should be set up in a lathe and the bore trued up OR a special pilot bushing should be made that runs out the same amount as the crank bore. The run out in the bore of a pilot bushing is put 180 degrees off from the crank bore run out and the pilot bushing installed. If properly done, this can put the bore of the pilot bushing well within the 0.003" required. We have used this method to save engine disassembly many times. A disadvantage of this method shows up at pilot bushing replacement time as a special pilot bushing will have to be reproduced."</blockquote>  

The flutes reduce the load bearing capacity- even though there's not a terrific amount of load on the pilot bushing- provided the bellhousing is indexed correctly. They also present a way for contaminants to get into the bushing. <br style="clear:both"/>

|[[File:Galled input shaft.jpg|thumb|center|225px|Badly galled input shaft caused by seized pilot bushing containing a high amount of iron or steel]]

A pilot bushing containing a good amount of iron or steel in the material's composition can and will cause this type of galling. It comes from a under lubricated, over worked condition that causes microwelding of the shaft to the bushing under extreme conditions of heat and load. Somewhere in the shaft's life, it has been used w/a iron/steel compound bronze bushing by the looks of it.

An all bronze oilite bushing is basically incapable of such damage, the bronze being softer than the shaft causes the bushing to be sacrificed instead of the shaft.

===Bearing (rolling element)===

It's been stated that the roller needle bearing has a Rockwell hardness of about 57 and the newer transmission's gears are rated between 61 and 63.

|[[File:GMHD pn 14061685 needle brng pilot brng.jpg|thumb|center|300px|GM p/n 14061685]]

First, when removing the bearing you will be removing the transmission. So, as anytime, when doing these changes ''be safe'' and have the vehicle properly secured when lifted in the air, if you do not have a lift. Be sure to use the proper jack stands for the weight of the vehicle in question, and, if possible, have someone there with you while performing the work. DO NOT place vehicle on blocks of wood or concrete blocks. If you have access to a transmission stand, use it by all means.  

Vehicle needs to be on a good level surface. After the transmission has been removed and cleared from the vehicle, you will remove the flexplate/flywheel. Then, if you look at the end of the crankshaft, you will see the bushing. It is where the shaft of the transmission will ride when installed. The nose of the shaft sits inside the bearing. Now you can either rent or buy a puller for this. It's a small slide hammer puller with fingers on it that you will place in the bearing and use it to pull the bearing out. If you do not have access to a puller here are a few other ways of removing the bearing.

*You can fill the center of the bearing with grease and find something that is almost the same size as the bearing and place it in through the center of the bearing and take a hammer and hit whatever you are using and the force with the grease behind the bearing will force it out. You might have to hit it pretty hard and more then once but it will come out. '''When using something like grease, wear safty glasses and leather gloves. The force of the grease can cut the skin, or even put your eye out. Also watch out for flying pieces of metal.'''

*If you have a brass or bronze pilot bushing, an alternate method can be used as well. Use a tap and cut threads into the bushing. Then screw in a bolt and bottom it out inside the bushing so it contacts the crank. Then just keep on turning and it will pull the bushing out. Works real well if you have a tap, where as you may not have a piece of stock to fit the bearing inside diameter.It is a little safer as it takes the hammer out of the equation.