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Has anyone ever experienced a spun pilot bushing in the crank. I pulled the tranny in a mid year coupe today for a clutch noise. On getting the clutch out, I was going to change the pilot and it literally fell out in my hand when I pulled on it. The outside surface is scored and the input shaft had some minor marks on it. The pilot is noticeably smaller when placed on a new bushing....
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Re: Spun pilot bushing....
Bruce-----
Some replacement pilot bushings, including the ones that GM sold for awhile, were of slightly smaller OD and do not have a sufficient interference fit in the crankshaft. I'll bet that yours was replaced at some point with one of these.In Appreciation of John Hinckley -
Re: Spun pilot bushing....
Bruce,
I've seen a few of these over the years. Two likely possiblities. First is an incorrect alignment of the clutch housing to engine. This can easily be checked using a dial indicator. Clamp or attach the indicator to the end of the crankshaft and indicate the ID of the clutch hsng opening.
The other, more likely cause, is a clutch disk that is severly out of balance. It's actually quite common, especially on aftermarket disks. The constant pounding will eventually cause the pilot bushing to loosen and eventually rotate eccentrically.
A third unlikely possibility is if the pilot bushing is/was a cheap aftermarket replacement, it may have become attached to the transmission input shaft if the car was stored for a long time in a damp environment.
Likely the crankshaft is not damaged and a new GM bushing should fit properly.
MichaelComment
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Re: Spun pilot bushing....
Hi Everyone, I purchased a nice 63 a few years ago. When you ideled the car in neutral with the clutch out it made a noise like there was a dozen marbles in the tranny. The clutch worked fine and when you pushed the pedal in the noise went away. I expected bearing trouble in the tranny. When I pulled the tranny out there was no pilot bushing and no evidence of one being there for a long time. (the hole in the crank had lots of clutch dust in it) I put a new pilot bushing in and solved the problem. I guess Bubba lost that part.
BillComment
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Re: Spun pilot bushing....
Sounds like you have one of those rare powerglide 4 speed cars. Wasn't sure what it wanted to be when it grew up.
Bubba said ya really don't need all that stuff in there anyway.Comment
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Re: Spun pilot bushing....
Hi Mike....Clutch was brand new 3 weeks ago, Luk. Customer complained of clutch chatter and then the noise started.............Comment
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Re: Spun pilot bushing....
Bearing must have come loose almost immediately after the clutch was installed? Was the bushing replaced at that time?Comment
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Re: Spun pilot bushing....
Yes....bushing was replaced at the time of the first clutch change.Comment
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Did you balance the clutch disk and pressure plate
Yes, I _know_ the manufacturer balances them, but I have found lots of drill marks in mine when I get them back from the machine shop for balancing. Some have been quite large, like several grams.
So much for the manufacturer's balancing machine.Comment
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Re: Did you balance the clutch disk and pressure p
Mike....Did you send the clutch and flywheel or the complete reciprocating assembley? (ie, crank, rods,etc) I've never heard of anyone sending JUST the clutch for balancing, but I understand the principal. I know when I've built engines the clutch has gone to be blueprinted too. But when you are just replacing the clutch it never ocurred to me............Comment
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Re: Did you balance the clutch disk and pressure p
Yes, I sent out the presure plate and disc without anything else. Every clutch and pressure plate I ever bought I sent out, with the exception of the first. When the first would vibrate at 3500 rpm, I knew something was wrong.
I've found the best results is to find my own machine shop, as opposed to having the parts store send them out. They usually resist, telling you it is already balanced. I had one store that told me it was balanced and there were no drill or weights anywhere on it. When I asked to speak to the shop manager, they decided not to charge me.Comment
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