The Pesky Pilot Bearing
Last week Dabney Dufus was in the process of replacing the clutch on his "mint condition" original 1964 Chevy II. Like all thorough mechanics he had purchased the complete clutch set, including the disc, pressure plate, throwout bearing, alignment tool and pilot bearing. Everything was going along smoothly and the tranmission had come out without fuss.
After removing the pressure plate he started on the task of removing the old bronze pilot bearing that was pressed into the center of the end of the crankshaft. That's when things got a little frustrating. Dabney was hooking up his air saw as Dr. Crankshaft stuck his head in the door. "Whatcha doing, Dab old boy?" asked the Doctor.
"Replacing the clutch in this Chevy II."
"Ok," said the Doctor, a little amused. "Watcha going to use that for?" he said, pointing to the air saw.
"To take out the pilot bearing." Dabney had convinced himself that this was the only way go about it.
Dabney continued: "I tried to grab it with inside gear pullers and wedging a couple of screwdrivers in the opening, but all I did was create deep scratches and galls in its surface. Now it has to come out...It didn't want to come out the easy way, so now I'm going to do it the hard way. I'm going to saw out a little section of it to relieve the interference fit and get it out," replied Dabney feeling smug. Sometimes he just feels the need to demonstrate to the Doctor how much he understands about automobile engineering.
"Well, isn't that interesting?" said the Doctor. "I'm impressed. What kind of blade are you using on that saw?"
Dabney was beginning to "feel his oats" now. "Coarse, of course! Any dummy knows that you use a coarse blade so that your saw will cut only the bronze of the bearing with minimal damage to the steel of the crankshaft."
"Looks like you've got things under control here, Dabney, I guess I'll be moseying along."
"Yeah, Doc. Thanks for stopping by." Dabney was really feeling great that he figured it out on his own, and the Doctor was stuck with no advice to give.
The Doctor was about a step or two past the door and he said "Of course, I would just use some grease."
Dabney walked over to the compressor and flipped the switch. The compressor sprang to life. Dabney watched the pressure gauge a couple of seconds and said "What?" in a loud voice. He turned off the compressor and ran to catch up with the Doctor.
"What do you mean you 'would just use some grease'?" he asked as he caught up.
"I'd use grease to get the pilot bearing out. But as you said, 'Any dummy knows that you use a coarse blade' and I didn't want to insult you." said the grinning Doctor Crankshaft.
"OK, just how would you use grease get the pilot bearing out?" asked Dabney. "Grease won't loosen an interference fit."
"You're right, Dabney, it won't," said the Doctor as he put his hand on Dabney's shoulder and re-directed him back to the garage, "but it will get that pilot out lickety-split."
Once back in side, Doc said "I need some wheel bearing grease, a wooden stick and the clutch alignment tool you got with your clutch rebuild kit." Dabney provided the requested items. Slipping under the car the Doctor took the wooden stick and packed the pilot bearing's hole with grease until no more would go in.
"Hand me that clutch alignment tool and a rubber mallet" said the Doctor. Dabney handed it to him. "Be careful with that alignment tool, Doc, if you damage it the clutch plate will be hard to align."
"Yeah, yeah. Don't you worry your little young head," said the Doctor, as he placed the alignment tool into the opening and tapped the rubber mallet against its end.
In seconds the pilot bearing popped out of the end of the crankshaft, accompanied by films of grease. "Here it is, old boy. Now all you have to do is clean out the rest of the grease and tap in the new bearing. Nothing to it!" said the Doctor.
Before Dabney could utter a word the Doctor said, "You see, the grease created hydraulic pressure behind the bearing, amplifying my tapping of the alignment tool. It's just as if I were pressing it out from inside," said the Doctor.
Resigned to the fact that the Doc, once again, had a better way, Dabney was beginning to feel a little better knowing that the Doc did get the bearing out. "Thanks Doc," he said.
"No problem, Dab...Why don't you come over to the house for dinner, tonight. The Missus has some more uses for grease that you probably haven't thought of."
The Doctor saw the look on Dabney's face and said "I'm just teasing you Dab. Come on over for dinner, we'll be glad to have you."
Remembering that the Doc's wife was an excellent cook, perked Dabney up quite a bit. "I'd be happy to, Doc! I'll be there."