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10-18-2017, 11:59 AM | #1 |
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Pilot bearing to main gear drive fit
Can anyone tell me how much clearance I should have between the bore of the flywheel pilot bearing and the end of the transmission main gear drive? I have both a new bearing and a new drive, and right now there is only .0003 (three ten-thousandths) clearance between them. I can get the bearing on the shaft, but it requires some persuasion. I'm just afraid that when I'm laying on my back under the car in a snowbank, bench-pressing the transmission up into place and using my foot to shove the transmission into the clutch plate/pilot bearing, that it's not going to want to go.
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10-18-2017, 01:12 PM | #2 |
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Re: Pilot bearing to main gear drive fit
you WANT it to be a snug fit - you do not want that bearing center to spin on the shaft what so ever. If it fits with minor persuasion by hand leave it alone. Most people pin prick a used shaft so it presses in tighter.
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10-18-2017, 01:16 PM | #3 | |
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Re: Pilot bearing to main gear drive fit
Quote:
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10-18-2017, 11:02 PM | #4 | |
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Re: Pilot bearing to main gear drive fit
Quote:
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10-19-2017, 10:23 PM | #5 | |
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Re: Pilot bearing to main gear drive fit
Quote:
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10-20-2017, 07:28 AM | #6 |
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Re: Pilot bearing to main gear drive fit
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I never thought about clearances on these and somehow managed to assume the needed pretzel position on the garage floor to get them in place. Last time I installed one I did it from the top (in a 52 F!) and cheated with my engine hoist. Took me 71 years to figure that one out. Fear of getting stuck in the pretzel position was a real motivator. |
10-20-2017, 08:55 AM | #7 |
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Re: Pilot bearing to main gear drive fit
Chamfering or beveling the end of the input shaft will help getting it started, .002 loose fit is what I would work for. Main engine bearing clearance is .0015
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10-20-2017, 09:20 AM | #8 | |
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Re: Pilot bearing to main gear drive fit
Quote:
IIRC that bearing is a 6203 which has an ID of 17mm (.6693")
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10-20-2017, 11:19 AM | #9 |
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Re: Pilot bearing to main gear drive fit
Should be a tight slip fit on the in put shaft.
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10-20-2017, 05:47 PM | #10 |
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Re: Pilot bearing to main gear drive fit
A slip fit is what I was thinking it should be. When I get back to town this weekend I'll chuck it (shaft) up and hit it with some sandpaper. Thanks for your help, everyone!
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10-21-2017, 01:15 AM | #11 |
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Re: Pilot bearing to main gear drive fit
Do not use sandpaper. .002 is too much on the bearing to shaft clearance. With that clearance it will wobble (like a crank shaft bearing will, but they have oil, which the pilot bearing does not.) Keep it snug, the .0003 does not seem excessive tight to me.
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10-21-2017, 09:34 AM | #12 |
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Re: Pilot bearing to main gear drive fit
Note that it only works when the clutch is released, 99% of the time it's not turning.
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10-21-2017, 10:42 AM | #13 |
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Re: Pilot bearing to main gear drive fit
When I was checking the fit the other day, I had to use a hammer and brass drift to get the bearing started. I only put it on about half way and had to use a bearing puller to get it back off.
How does one install a transmission if the bearing fits that tight in both the flywheel and on the shaft. It's not going to slide into place using the weight of the transmission alone, and I think using the mounting bolts will distort the bell housing. Or will they? I've installed a lot of transmissions (granted, newer models that don't have the main gear hanging out there) and the pilot bearing was a slip fit to the shaft, not a press fit that I have now. Am I wrong on this?
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10-21-2017, 06:30 PM | #14 |
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Re: Pilot bearing to main gear drive fit
Yes, that's too tight. I've never run into that problem, but my first guess would be the bearing size, so I'd try another bearing. It's the same as the front bearing on the generator.
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10-22-2017, 09:26 AM | #15 |
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Re: Pilot bearing to main gear drive fit
Thanks Tom. I didn't have a spare bearing, so ended up using the lathe/ sandpaper method. I took an additional .0006" off the shaft and the bearing is a good, snug, slip fit now. It has just under .001" clearance now and fits like I expected it to.
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10-22-2017, 11:59 AM | #16 |
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Re: Pilot bearing to main gear drive fit
That is a trick that some restorers use with a worn input shaft. A new metric ID bearing, and then turn the nose on the shaft to fit.
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