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Old 11-15-2018, 11:09 PM   #1
braol
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Default Main Shaft in Trans is worn...

Hello!
So, I started taking my transmission apart and the main shaft seems to be worn. Where it slides into the Main Drive Gear it is worn around the edge of the roller bearing (see next to tip of screw-driver in picture). The Main Drive Gear also rocks all around in it's ball bearing (see video). My questions for the pros out there are:

1) Is the small 'lip' on the Main Shaft supposed to be there and it is just the roller bearing that is bad? (I got new bearings that I am going to test fit on the shaft when I get it out.
2) Since I don't have the shaft out yet, any theories as to why the shaft rocks so much before disassembly??
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Last edited by braol; 11-16-2018 at 10:17 PM. Reason: add picture
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Old 11-16-2018, 08:27 AM   #2
Tom Wesenberg
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Default Re: Main Shaft in Trans is worn...

The front shaft is held in a straight line by the crankshaft bearing and front tranny case bearing. The output shaft is held in a straight line by the pocket bearing and rear tranny case bearing. Depending on the time period, the output shaft has a built in lip, or a separate spacer for the pocket bearing (transmission main shaft pilot bearing).
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Old 11-16-2018, 10:20 PM   #3
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Default Re: Main Shaft in Trans is worn...

Turns out that my ball bearings were installed with the open faces facing OUT of the transmission!

I just can't seem to download any pictures...
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Last edited by braol; 11-16-2018 at 10:34 PM.
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Old 11-16-2018, 10:37 PM   #4
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Default Re: Main Shaft in Trans is worn...

QUOTE: The Main Drive Gear also rocks all around in it's ball bearing (see video).

I cannot see your video. However, the situation described is normal for a ball bearing supported assembly and should be less pronounced with a new bearing.
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Old 11-17-2018, 10:27 AM   #5
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Default Re: Main Shaft in Trans is worn...

Quote:
I just can't seem to download any pictures...
In the "Quick Reply" section click on "Go Advanced", then click on the paperclip icon.
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Old 11-17-2018, 11:09 AM   #6
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Default Re: Main Shaft in Trans is worn...

I wish I had a brand new as Ford made it transmission to observe what I have seen in what was called out for in the ball bearing fit or classification.I do know from my bearing supplier that there is or I should say was ball bearings made with more tolerance than others,mayby this is good or bad. What I have osberved lately is the China bearings that I had fit on the main shaft bearings with no wobble at all but the much more expensive USA SKF bearings that were matched up from my originals do have a slight wobble or movement not on the press fit but ball bearings themselves. I have observed this in several other original or what I think are OEM bearings but not the China ones.So my conclusion is that some movement or alignment was engineered in so the two shafts would work better together? A tight no wobble bearing would seem to be desired but may eventually build up more heat from friction? I don't know for sure but I do know that with a China bearing you do not get much of a choice in grade or fit as you once did with USA or any of the other countries like Germany ,Italy and Sweden among many others who made very fine bearings.
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Old 12-06-2018, 01:34 PM   #7
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Default Re: Main Shaft in Trans is worn...

All put together now. New main shaft from Brattons was overspec and my gears wouldn't slide on. I am sending it back for a refund.
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Old 12-06-2018, 02:44 PM   #8
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Default Re: Main Shaft in Trans is worn...

The link below will take you to a pictorial document about the overhaul of a Model A transmission. It is long and tedious, 73 pages. On page 30 it addresses the question about the main shaft. Keep in mind there are two different shafts. The early shaft has a bearing spacer that is integral to the shaft. The late shaft has a removable spacer that is shaped like a key ring. It is prudent to replace it at each overhaul as they are usually worn flat on the front surface.


https://www.santaanitaas.org/wp-cont...ugust-2018.pdf


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Old 12-06-2018, 03:30 PM   #9
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Default Re: Main Shaft in Trans is worn...

Quote:
Originally Posted by braol View Post
All put together now. New main shaft from Brattons was overspec and my gears wouldn't slide on. I am sending it back for a refund.
I had the same problem when I bought the transmission rebuild package for my '31 CCPU. Their new main shaft was too big for their 2nd /3rd gear slider. I ended up using my old main shaft and everything worked out fine.
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