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?

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).

Re: Pilot Bearing Question
 

I wouldn't worry about .002"

Re: Pilot Bearing Question
 

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.

Tom Endy

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.

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.

Joe K

Re: Pilot Bearing Question
 

I was advised against that. Due to the thinner turning, the nose loses strength and can break due to torsional stress.

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.

Re: Pilot Bearing Question
 

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.

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.

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?

Re: Pilot Bearing Question
 

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.

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!

Re: Pilot Bearing Question
 

.002" is half thickness of a human hair and that of an engine crank bearing clearance.

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.

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.

Re: Pilot Bearing Question
 

For sure? I think the rolling movement when pedaling the clutch is taken over by the roller bearing?

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.

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.

Re: Pilot Bearing Question
 

I agree with Joe K (#6 post). Now is the time to correct the issue since it’s out. The shaft is going to turn in the pilot bearing as it has already so it’s going to wear smaller yet. As mentioned, getting it turned is easy for any machine shop. Also it seems most machinists have their own lathes at home and may do it for you. I’ve had them turned to 5/8” by a retired tool and die maker. The bearing originally was metric at 17 mm. That few thousandths will clean-up most shafts and has never been a problem strength-wise. You can buy bearings at most bearing shops. I get mine on Amazon Prime.