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Old 12-24-2019, 01:07 PM   #1
gw
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Default Pilot Bearing Question

The pilot bearing does not fit snugly on the trans input shaft. Measuring shows that the shaft is .002 smaller than the pilot bearing. Is this a problem? If so, could a brass shim ring be used?
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Old 12-24-2019, 01:31 PM   #2
Werner
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Default Re: Pilot Bearing Question

Hallo gw,

if the shaft can move inside the bearing seats, this is not a good thing because the main bearing wears out faster. A brass sleeve is difficult to manufacture because the wall thickness is too small.

I minimized the movement by glue a steel strip (0.1 mm) round the pilot stump (Locktite).
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Old 12-24-2019, 02:51 PM   #3
Patrick L.
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Default Re: Pilot Bearing Question

I wouldn't worry about .002"
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Old 12-24-2019, 10:45 PM   #4
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Default Re: Pilot Bearing Question

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I wouldn't worry about .002"
I'm with Pat. Clearance of .002 is little more than a sliding fit. Not sure the mods described are warranted. For serious slop a new input shaft/pilot bearing would be more cost effective IMHO.
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Old 12-25-2019, 12:37 PM   #5
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Default Re: Pilot Bearing Question

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I wouldn't worry about .002"
As long as you have the transmission removed, fix it. .002 problem or not, shaft will continue to wear. Find a good machinist to weld and turn down or use a sleeve. Pulling and installing the transmission is no fun.
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Old 12-24-2019, 02:58 PM   #6
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During a transmission overhaul it is common to find most input shafts with the nose end worn. I take them to a local repair shop where they machine the nose down and press on a drill bushing of the proper size.

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Old 12-24-2019, 04:18 PM   #7
Werner
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Default Re: Pilot Bearing Question

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... I take them to a local repair shop where they machine the nose down and press on a drill bushing of the proper size.

Tom Endy
I was advised against that. Due to the thinner turning, the nose loses strength and can break due to torsional stress.
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Old 12-24-2019, 03:08 PM   #8
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Default Re: Pilot Bearing Question

Tom, your fortunate to be able to get those kind of services done for you. I suspect the volume of your work makes that more worthwhile for a machinist. Always enjoy seeing your posts.
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Old 12-24-2019, 03:19 PM   #9
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Default Re: Pilot Bearing Question

I would say 0.002 IS worth worrying about. One of the reasons for "jerky" engagement and walking the 3rd gear internal gear "off" the input shaft. (i.e. slipping out of 3rd back to neutral)

Best would be to turn it down, bush it back a tad oversize, and with emery cloth go for a "tight" fit.

Cheap insurance.

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Old 12-24-2019, 09:49 PM   #10
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Default Re: Pilot Bearing Question

Any good machine shop can fix it. One way is to tig weld it up and turn it to size so bearing just slides on. I have done many this way.
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Old 12-24-2019, 11:04 PM   #11
Chuck Sea/Tac
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Default Re: Pilot Bearing Question

They make a smaller inner diameter 6203. Metric I think. Turn the nose down and use that bearing. I’m rebuilding my transmission after 40,000 miles of this bearing. It’s worn a little more now, so were I to reuse the otherwise good input shaft, I would turn and sleeve back to standard, as Tom mentioned.
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Old 12-24-2019, 11:11 PM   #12
1ton
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Default Re: Pilot Bearing Question

.002 clearance is fine but the pilot on your input shaft looks to be worn. How can you get a good measurement on that?
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Old 12-25-2019, 12:52 PM   #13
Jim Brierley
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Default Re: Pilot Bearing Question

I agree with Pat L and mulletwagon. .002" is miniscule, and the only time that brg. is turning is when the clutch is pushed down and the car isn't moving. Don't worry about it!
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Old 12-25-2019, 02:10 PM   #14
Patrick L.
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Default Re: Pilot Bearing Question

.002" is half thickness of a human hair and that of an engine crank bearing clearance.
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Old 12-26-2019, 10:26 AM   #15
Ranchero50
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Default Re: Pilot Bearing Question

Gotta have some clearance or the input to bushing fit will seize while sitting at a stop light with the trans in gear and the clutch held.
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Old 12-26-2019, 11:41 AM   #16
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Default Re: Pilot Bearing Question

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Gotta have some clearance or the input to bushing fit will seize while sitting at a stop light with the trans in gear and the clutch held.
For sure? I think the rolling movement when pedaling the clutch is taken over by the roller bearing?
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Hercules W 2000, 1976; (with NSU-Wankel Rotary Engine), Canadian version
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Old 12-26-2019, 10:59 AM   #17
Patrick L.
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Default Re: Pilot Bearing Question

While most vehicles use a bushing for a pilot 'bearing', most Model As use a ball bearing. I have seen a couple old Fords with a bushing though. A properly oiled oil-lite bushing would work just fine. As you mention, some extra clearance would be necessary.
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Old 12-28-2019, 09:58 PM   #18
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Quote:
Originally Posted by Patrick L. View Post
While most vehicles use a bushing for a pilot 'bearing', most Model As use a ball bearing. I have seen a couple old Fords with a bushing though. A properly oiled oil-lite bushing would work just fine. As you mention, some extra clearance would be necessary.
Mine has a bushing, wasn't aware that they had bearings at one time.
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Old 12-27-2019, 09:55 AM   #19
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Default Re: Pilot Bearing Question

Push fit is anywhere from .001" to .0015". .002" is good for a rotational clearance that doesn't need to be a push fit. I've seen the V8 flywheels with the old phosphor bronze bushing worn egg shaped and they were still working albeit not as well as they should. Now if it was more than .002", then I'd start to get concerned. The input shaft bearing has clearance too or the bearings would last very long.

Rotating bearing fits have to have some clearance or there can be galling from excessive temperature built up. The only time the pilot really turns is when the clutch is released. Folks that stand on the clutch too long will experience more wear. Put the transmission in neutral and release the clutch.
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Old 12-27-2019, 04:02 PM   #20
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Default Re: Pilot Bearing Question

That's true, if rolling bearings run under tension, they are quickly destroyed.

In my case, the worn undersize is 0.007"! This is extreme and the new main ball bearing would wear out quickly again.
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