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Old 12-16-2019, 11:25 AM   #1
Kentmac
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Default Transmission gear/shaft question

In the process of working on the transmission in my model A and need some advice. I am replacing all the bearings and discovered the main shaft (not gear shaft) has some scoring so I ordered a new main shaft and received it from Snyders. The issue I am having is that the gears were difficult to install on the main shaft and do not slide freely back and forth. I put some grease on the shaft and can move the gears by hand but I think they are too tight. Any advice would be appreciated
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Old 12-16-2019, 11:30 AM   #2
ryanheacox
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Default Re: Transmission gear/shaft question

You do want a reasonably tight fit. Can you slide them back and forth by hand? Someone has a write-up that states the gears should just barely slide down the shaft if it is stood up vertically.


Edit: it is on Jim Mason's website. http://jmodela.coffeecup.com/xmissionrebuild.html

Last edited by ryanheacox; 12-16-2019 at 11:31 AM. Reason: add info
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Old 12-16-2019, 11:36 AM   #3
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Default Re: Transmission gear/shaft question

The gears do not slide easily at all, I can move them but with quite a bit of effort.
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Old 12-16-2019, 11:37 AM   #4
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Default Re: Transmission gear/shaft question

They should slide but have no rocking play so they have to be a close fit. If they won't slide by hand push fit then the shaft may be a bit oversized. That's fine if gears are worn but not so good if gears have no wear. It's a good idea to check the dimensions the best you can and see where the clearance is the tightest. If it's on the OD of the shaft then that should be no problem but if it's in the splines then that could be a problem.
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Old 12-16-2019, 01:58 PM   #5
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Default Re: Transmission gear/shaft question

There is a Ford service bulletin that states there should be .002 clearance between the shaft and the two slider gears. The bulletin went on to say that when replacing any one of the three parts, they all should be replaced as a matched set. One would think that Henry Ford hired Henry Aldridge to sit in the stock room and match up shafts and gears. It was also a good way to increase parts sales. Whatever was the case, Henry Aldridge would have retired years ago, and today there is no such thing as a matched set from a supplier.

When I put a transmission together I check to make sure the slider gears move on the shaft freely and without a lot of slop. It is very difficult to get a match with reproduction parts.

Before I would buy a reproduction main shaft I would have the original that works well with the slider gears repaired. The worn front end bearing surface can be machined down and hardened drill bushings of the proper size pressed on. This is not a difficult machine shop process. Jim's Automotive Services in Costa Mesa, CA 714-546-2969 provides this service.

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Old 12-16-2019, 02:01 PM   #6
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Default Re: Transmission gear/shaft question

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If you want to loosen them up or indicate where the rub is, put a very small amount of lapping compound ( fine or extra fine) on the shaft and slide one gear at a time back and forth on the shaft - this is done with the splined shaft and the gear on the bench, not in the housing. Do all of the gears one at a time. Leave no compound after, wash in solvent and soap after the solvent.
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Old 12-16-2019, 03:08 PM   #7
Jim Mason
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Default Re: Transmission gear/shaft question

Lube with your xmisson lube, stand the shaft on end. gear should slide down by its own weight or with light finger pressure.
I have a mediocre articke on my site, Tom Endy has a better one somewhere.

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Old 12-16-2019, 03:22 PM   #8
J Franklin
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Default Re: Transmission gear/shaft question

I think as long as they can be moved with drag you will be all right. Too loose causes problems with popping out of gear.
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Old 12-16-2019, 03:25 PM   #9
Kentmac
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Default Re: Transmission gear/shaft question

Thanks for all the replies, I tried moving the gears back and forth on the shaft but did not have any luck. I called Snyder's and they acknowledged that there were some problems with some shafts. They are going to send me another and test it with gears before they send it out. I had another suggestion that might also have worked and that was to use a brake cylinder hone, as I didnt have one, I opted for the new one, hopefully it will work.
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Old 12-16-2019, 04:13 PM   #10
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Default Re: Transmission gear/shaft question

See attached article.

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File Type: pdf B9-Transmission Mainshaft.pdf (81.7 KB, 85 views)
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Old 12-17-2019, 01:19 AM   #11
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Default Re: Transmission gear/shaft question

I had the exact same problem with a new shaft that I purchased from Snyders. The solution for me was to mount the shaft in a small lathe and used some medium grit emery cloth with no lubricant. I spun the shaft and looped the emery cloth around it and removed about 0.002-0.003. The gears then slid on the shaft freely with no problems.
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Old 12-18-2019, 11:54 AM   #12
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Default Re: Transmission gear/shaft question

Ditto what you said AGBill. I received a new shaft from Snyders yesterday and there was no way the low/reverse or second/high gears would even go on it (without a hammer). Took it to a friends place this morning, chucked it up in his lathe and after 15 minutes or so with the emery cloth (sneaking up on the proper fit) had them both on the shaft and sliding perfectly.
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Old 12-18-2019, 02:26 PM   #13
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Default Re: Transmission gear/shaft question

Snyders - if you read these posts, you need to do the following:

1. Take all the shafts in stock to a local machine shop and have them remove a few thousandths off the outside diameter of the shaft. Bring along an original sliding gear that the shop can use as a (go/no go) gage for the proper diameter. After the shafts have been modified, put them back on the shelf for sale to customers.

2. Change the existing fabrication drawing for the shaft by reducing the drawing maximum dimension for the outside diameter by 0.003 - 0.004 thousandths. This will prevent future batches of the shaft from having the same problem.

Keep your customers happy!
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Old 12-18-2019, 02:56 PM   #14
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Default Re: Transmission gear/shaft question

Quote:
Originally Posted by AGBill View Post
Snyders - if you read these posts, you need to do the following:

1. Take all the shafts in stock to a local machine shop and have them remove a few thousandths off the outside diameter of the shaft. Bring along an original sliding gear that the shop can use as a (go/no go) gage for the proper diameter. After the shafts have been modified, put them back on the shelf for sale to customers.

2. Change the existing fabrication drawing for the shaft by reducing the drawing maximum dimension for the outside diameter by 0.003 - 0.004 thousandths. This will prevent future batches of the shaft from having the same problem.

Keep your customers happy!
On the other hand, it is possible that the vendors' main shafts are sized to match the gears they sell and are not to the original Ford specs.

Also, I have found that even a new and unused NOS Ford main shaft may well be too loose when mounted with used original Ford gears. In that case, the slightly oversized repop main shaft is a good thing because you can chamfer it down to achieve a close fit for better performance. Call it making lemonade from lemons.

I have also found that original Ford gears may not mix well with repop gears - noisy or jumping out of gear - and it is usually best to install all the gears in one case with one source or the other.
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Old 12-18-2019, 07:06 PM   #15
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Default Re: Transmission gear/shaft question

If they are oversized then that would be handy with an old worn set of gears but they should be marked as such. This has been a problem with some reproduction parts over the years. It boils down to the manufacturer's quality control.
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Old 12-18-2019, 09:27 PM   #16
J Franklin
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Default Re: Transmission gear/shaft question

One size (can) fit all!
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Old 12-20-2019, 02:14 PM   #17
Kentmac
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Default Re: Transmission gear/shaft question

Got my replacement shaft yesterday and installed it today. Quick response from Snyder's.
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