arbor shim size for pinion shaft

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Paul Bjarnason

Senior Member
I am out of town and want to get in an order for some arbor shims for the pinion gear of my '29 Tudor, to reduce the excessive backlash which I asked the Barn about a couple of days ago. I got some good suggestions from fellow Barners which I want to act on as soon as I get home. So I can get the order in tonight, I would appreciate it if someone could tell me what the pinion shaft diameter size is. Also, the usual suppliers do not seem to carry the arbor shims, but I expect I can get them at a machine shop or industrial supply house. Thanks.
 
I measured a pinion gear I have and it measures 1.575”. The shoulder wear the bearing seats measures 1.870”. Hope this helps . Dennis
 
That is not how you do the back lash. Read Tom Endys how to do. Moving the pinion out moves the teeth further apart. You need to adjust the backlash by ether gaskets or shims under ether the bearing or cups in the axle tubes or on the carrier its self.
 
redmodelt said:
That is not how you do the back lash. Read Tom Endys how to do. Moving the pinion out moves the teeth further apart. You need to adjust the backlash by ether gaskets or shims under ether the bearing or cups in the axle tubes or on the carrier its self.
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I must have read Tom Endy's how-to more than ten times. Tom does not mention putting an arbor shim to move the pinion in further on the ring gear. He only mentions moving the banjo shims from the left side to the right side, once the total number of shims has been determined or shimming the ring gear bearings. I will first try what Tom says, but I doubt it will be sufficient as my backlash is so great, i.e., .040 or 1 mm. Perhaps my gear set is so worn I need to buy replacements. We'll see. Will report back.
 
For setting up the backlash in a Model A rear end, I recommend the Best Gasket Company for purchasing rear end gaskets. The Model A rear end gasket set from Best Gaskets has gaskets of several thicknesses so that the proper setting for clearance and backlash can be obtained. The Model a vendors usually only have gaskets available in two thicknesses. There is a shim available from vendors such as Bratton's if it is required to space the bearing races away from the housings.

Setting the rear end up is basically a trial and error procedure and Tom Endy is the man when you have questions.
 
I am not familiar with the term arbor shim, but if you are looking for a shim that fits over the pinion gear sleeve Bratton's carrier shim p\n 6071, which is .005 thick will slide right over the pinion sleeve. This is because all four tapered bearings in the differential are all the same part number. The Bratton shims are designed to be used on the carrier hubs, but they will also fit on the pinion sleeve.


However, installing shims on the pinion gear sleeve is a useless exercise. Adding a shim behind the first bearing pushes the pinion gear further aft. Alternately, taking a cut on the pinion bearing stop will move it in the opposite direction. People who have become convinced that bluing the ring & pinion is necessary through bad information have come to the conclusion that one of these option is necessary. None of this is necessary to properly overhaul and set up a Model A differential.


The first effort in the differential rebuilding process should be to set the carrier preload. This is done through a trial and error effort to determine how many banjo gaskets are required. Carrier shims may also be required in some cases. Once this is done the pre-load on the pinion gear assembly is set by adjusting the two large nuts on the pinion sleeve.


The third effort is to set the backlash. This is done through trial and error of moving the previously selected banjo gaskets left\right. This will move the ring gear either closer or further away from the pinion gear.


Moving the pinion gear fore and aft is not necessary. In 30 years I have rebuilt over 800 Model A differentials and have never found a shim on a pinion sleeve, or evidence of the bearing stop being machined.

If you go to the web site of the Santa Anita A's of Arcadia, California at www.santaanitaas.org , on the home page is my name, click on it to go to a tech library. Go to the differential section and pull up the article dated 2014. This is a tutorial that will explain and show in pictorial detail exactly how to rebuild a Model A differential.


Tom Endy
 
Tom Endy said:
I am not familiar with the term arbor shim, but if you are looking for a shim that fits over the pinion gear sleeve Bratton's carrier shim p\n 6071, which is .005 thick will slide right over the pinion sleeve. This is because all four tapered bearings in the differential are all the same part number. The Bratton shims are designed to be used on the carrier hubs, but they will also fit on the pinion sleeve.


However, installing shims on the pinion gear sleeve is a useless exercise. Adding a shim behind the first bearing pushes the pinion gear further aft. Alternately, taking a cut on the pinion bearing stop will move it in the opposite direction. People who have become convinced that bluing the ring & pinion is necessary through bad information have come to the conclusion that one of these option is necessary. None of this is necessary to properly overhaul and set up a Model A differential.


The first effort in the differential rebuilding process should be to set the carrier preload. This is done through a trial and error effort to determine how many banjo gaskets are required. Carrier shims may also be required in some cases. Once this is done the pre-load on the pinion gear assembly is set by adjusting the two large nuts on the pinion sleeve.


The third effort is to set the backlash. This is done through trial and error of moving the previously selected banjo gaskets left\right. This will move the ring gear either closer or further away from the pinion gear.


Moving the pinion gear fore and aft is not necessary. In 30 years I have rebuilt over 800 Model A differentials and have never found a shim on a pinion sleeve, or evidence of the bearing stop being machined.

If you go to the web site of the Santa Anita A's of Arcadia, California at www.santaanitaas.org , on the home page is my name, click on it to go to a tech library. Go to the differential section and pull up the article dated 2014. This is a tutorial that will explain and show in pictorial detail exactly how to rebuild a Model A differential.


Tom Endy
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Thank you for weighing in, Tom. I have already read your tutorial, probably 10X. It was my "Bible" when I rebuilt my car's rear end and it helped me immensely. The pictures are terrific. On your saying it's a waste of time to move the pinion gear with a shim -- upon reflection, I have to agree with it would not be a good idea fit wise. While moving the pinion gear aft may reduce backlash, it would not hold up over time. The way I think about it is that the pinion and ring gear mesh a certain way when new and, as the gears wear, the pinion gear leaves a wear pattern in the ring gear. Moving the ring gear aft would disturb the way the pinion rides in the worn area on the ring gear. So, I will move the banjo gaskets from left to right, as you suggest -- and, if that doesn't reduce the backlash to .020 or less, I will replace the worn ring and pinion gears. I really do appreciate the tutorial you put together. It must have taken a great deal of time -- and, the photography is great. Thanks, again.
 
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I agree with what Tom says too, but I have built a few quick-change rears and have had to move the pinion towards the ring gear to get proper back-lash. I have never heard the term arbor shim either, but the way you describe your problem, something other than shimming the carrier bearings with gaskets is needed. 1st step would be to be sure all bearings are fully seated, then measure backlash. I have a shim-pack of assorted thickness shims, and cut my own shims the thickness I need. If you want to do a test of how far you need to move the pinion, cut a shim out of a tomato can, they are stronger than beer cans. If you find the backlash changes the amount you want, you know it is the right thing to do and only your labor time is involved. Sometimes you need to think out of the box! Good luck!
 
If the ring & pinion is not damaged there is no reason to replace it. If you are not able to reduce the back lash by moving banjo gaskets you can install shims on the carrier to move the ring gear closer to the pinion. Bratton's sells the shims, they are .005 thick. If you need more shimming you can add additional .005 shims. You will have to go back to the start and re-set the carrier pre-load if you add any shims.


I would get the back lash down to much less than .020. I think it should be less than .010. It is important that you do have some back lash otherwise you will be jamming the gears.


Tom Endy
 
John said:
For setting up the backlash in a Model A rear end, I recommend the Best Gasket Company for purchasing rear end gaskets. The Model A rear end gasket set from Best Gaskets has gaskets of several thicknesses so that the proper setting for clearance and backlash can be obtained. The Model a vendors usually only have gaskets available in two thicknesses. There is a shim available from vendors such as Bratton's if it is required to space the bearing races away from the housings.

Setting the rear end up is basically a trial and error procedure and Tom Endy is the man when you have questions.
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In doing my rear end I found the two available thicknesses of gasket wouldn't cut it. Some measurement with a micrometer brought me to GROCERY BAG material as about the right thickness that I needed. Trace with a pencil, cut with an X-acto knife and into the banjo where it has resided leak free for 30 years.

Glad there are more options.

Joe K
 
I make my own shim and put under the cup. I would rather take the cup out and not remove the bearings on the carriers any more then is absolutely necessary then to install a new bearing.
 
I just took the Jalopy's rear end apart, to fix two things: 1 - Although I had set the pre-load to 20 inch points, it was too much, as the bearing would difficult to turn and went in "fits and starts", like "clank, clank, clank"; and 2 - the backlash was way too much, at about 1 millimeter, i.e., .040 or so. I backed the pre-load off to about 10 inch points. It no longer "clanks", but it still has a little rumble when I turn it by hand. Do you think a little rumble is a problem? Seems like the only way to fix that would be to replace the bearings and race with another new set, as I can't see further backing off on the pre-load, which is now about half what it's supposed to be. Is it possible I damaged the new bearing set with the 20 inch pounds I initially set it to, where it "clanked"? I didn't turn it much, just a few turns. In the meantime, I will move the banjo gaskets around to see if I can reduce the backlash enough. Thanks in advance.
 
I moved as much gasket thickness as I could from the right side to the left, leaving just .003 on the right and .014 on the right. My backlash seemed to be about the same. But, then, I discovered what i thought was backlash between the ring and pinion gears wasn't backlash at all, but play in the spider gears. I figured that out by pulling off the left axle tube and looking at the ring gear when I twisted the drive shaft input -- there was no visible backlash. I pulled the axle shafts out and found that I could twist the left and right and there was play between the two occurring in the spider gears. I reached into the spider gear assembly and found that I could wiggle the spider gears individually, where they contacted the axle ends. So, that's where what I thought was backlash was occurring. Is that kind of "wiggle" in the spider gears O.K.?
 
I moved as much gasket thickness as I could from the right side to the left, leaving just .003 on the right and .014 on the left. My backlash seemed to be about the same. But, then, I discovered what i thought was backlash between the ring and pinion gears wasn't backlash at all, but play in the spider gears. I figured that out by pulling off the left axle tube and looking at the ring gear when I twisted the drive shaft input -- there was no visible backlash. I pulled the axle shafts out and found that I could twist the left and right and there was play between the two occurring in the spider gears. I reached into the spider gear assembly and found that I could wiggle the spider gears individually, where they contacted the axle ends. So, that's where what I thought was backlash was occurring. Is that kind of "wiggle" in the spider gears O.K.?
 
The ring & pinion back lash should be established before the spider gears and the axle shafts are installed.


if you have only a .003 banjo gasket on one side you are likely to have oil leaking on that side. I always make sure to have at least one .010 gasket on a side.


You can add a .005 metal shim under each carrier bearing and you will have to add additional banjo gaskets in order to re-set the pre-load. This will give you more latitude in shifting gaskets left\right.


Tom Endy
 
Paul Bjarnason said:
I just took the Jalopy's rear end apart, to fix two things: 1 - Although I had set the pre-load to 20 inch points, it was too much, as the bearing would difficult to turn and went in "fits and starts", like "clank, clank, clank"; and 2 - the backlash was way too much, at about 1 millimeter, i.e., .040 or so. I backed the pre-load off to about 10 inch points. It no longer "clanks", but it still has a little rumble when I turn it by hand. Do you think a little rumble is a problem? Seems like the only way to fix that would be to replace the bearings and race with another new set, as I can't see further backing off on the pre-load, which is now about half what it's supposed to be. Is it possible I damaged the new bearing set with the 20 inch pounds I initially set it to, where it "clanked"? I didn't turn it much, just a few turns. In the meantime, I will move the banjo gaskets around to see if I can reduce the backlash enough. Thanks in advance.
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There should not be any "fits and starts", "clank, clank, clank", or "rumble" in a tapered roller bearing! If these are new bearings, could they be mis-matched (that is, the wrong cup or cone for this application-I have seen where a cup had the right outer diameter, but wrong I.D.)? 20 in. lbs. is not too much preload. A rumble is usually from pitted surfaces. "Fits and starts" could be debris catching in the rollers, or "dents" in the races. I've seen this when a hammer is used on a cone to seat the cup, or using a press against a cone.
 
The carrier pre-load should be set before the pinion is installed and the pinion pre-load should be done without the carrier installed.
Are you using an inch pound torque wrench clicker type? You need to use a beam or dial type.

Are the bearings and cups new?
Back lash is tested with the carrier and pinion installed by turning the drive shaft. Installing axles and spider gears is the last thing I do.
I made up a spider with connector nut welded to it. Then use a long piece of all thread with socket to fit my torque wrench at the other. I also pointed the end that goes into the connector nut to make it easier to locate it.

I think I spent about 7 hours setting up my first ones. That's a lot of taking apart and moving things around to get it right.
 
OK, I think I got it right, now. I give thanks to everyone for their advice, which based upon the advice, I added to .005 shims under each of the carrier bearings, which gave me latitude to put adequate banjo gaskets and get the backlash right -- under .010. I got rid of the rumble and the clank, clank, clank, by backing off on the pinion pre-load to about 10 - 12 inch pounds. 20 inch pounds was to much. Thanks, again.
 
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