The Ford Barn

larrys40 · 03-17-2019, 06:24 PM

I agree with tom on his assessment. I have also torn down and rebuilt more than a couple hundred myself, i have two to do this week ... and have also never seen nor have ever had the call to use pinion shims. I agree that a carrier shim to move the ring gear closer is the solution. I’ve also never removed any original ones of those either. Are there anomolies,sure. But my bet is that the normal process will correct it with proper installed and parts to spec.

I do start with a.010 gasket on each side and find that’s generally close to the norm.
I do think it’s important to use Timken bearings and races as they are of a know quality and dimension.

Good luck
Larry shepard

steve hackel · 03-17-2019, 11:57 PM

Hello to all; "please" excuse the origin of my question, but with 41 posts and so many different opinions on the subject of shimming the pinion - can one of you post a picture or at least a sketch of how and where you are installing the shims to move the pinion into or away from contact with the ring gear teeth? I am "SO" confused...… Steve

redmodelt · 03-18-2019, 12:42 AM

You pull off the bearing on the carrier and add a shim behind it, or as I do behind the cup in the axle tube.

Tom Endy · 03-18-2019, 01:29 AM

Steve Hackel:

Photo shows a pinion gear: To the left is a shim that slides over the pinion sleeve to up against the stop right before the gear. The bearing goes on next to right up against the shim. This will push the gear toward the rear and away from the ring gear.

If you want to move the pinion gear forward instead of a shim you would have to chuck the pinion in a lathe and take some metal off the stop.

The same shim will fit over the hubs on the carrier assembly. The four bearings used in the differential are all the same part number.

Bratton's sell the shims. They are all .005 thick. If you need more shimming you can stack the shims.

Tom Endy

Dave in MN · 03-18-2019, 08:07 AM

Steve Hackel & Tom Endy:

The photo I have included shows where the shims are added to the assembly to move the pinion gear back. Placing the 5 (.005") shims in the location shown will move the pinion back .025" and decrease the backlash. Because the pinion gear is basically cone shaped, moving it back will cause a larger circumference area of the pinion gear to engage with the ring gear thus decreasing clearance between the gears and decrease the backlash. Left click on the photo and the increased photo size will show where the shims are placed in the assembly.

As Tom Endy states: "If you want to move the pinion gear forward instead of a shim you would have to chuck the pinion (gear) in a lathe and take some metal off the stop."
Taking a cut from the bearing stop on the pinion gear will move it forward in the assembly and increase the clearance and backlash between the ring gear and the pinion gear. FWIW: I have never seen it necessary to take a cut on the pinion gear stop on the rear ends I have worked on.
Good Day!

redmodelt · 03-18-2019, 10:34 AM

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Thank you Tom and Dave. I get it and understand.

steve hackel · 03-18-2019, 12:33 PM

Thanks for all the help and pictures : its just another weapon in the arsonal of tools and techniques needed to do the job the right way the first time!

denniskliesen · 03-18-2019, 03:45 PM

Model A differentials aren't as critical as far as gear mesh, compared to modern and high pressure use. My past experience with differentials has been Construction Equipment. You better make sure if working on one know what you are doing and do it properly, no guess work. Generally the depth of the pinion gear in relation to the ring gear is referred to as cone center. Dave in MN touches on this in his post #45 as saying the pinion is basically cone shaped. To get an accurate cone center means if you knew where the point of the cone is, then that point would be in relation to the center of the ring gear. That is where the pinion depth would need to be. Aftermarket gears and industrial applications have these numbers scribed on the gear set. They usually sell the tools to set and or measure the pinion depth for their gear sets if they are marked.
Otherwise you need to be able to check tooth contact pattern. You don't mismatch those gear sets. Most people will say it's not that critical to know what the backlash is precisely. I have never read or been told who does or has the tool to precisely measure backlash between ring and pinion. Finger feel is not good enough for me. Therefore I made tools to take the guess work or finger feel out of the equation. Granted I have not done hundreds of Model A differentials I have never had a Model A differential fail that I worked on. And I have the tools to accurately measure backlash. But seldom does a Model A ring and pinion that I have been told or read about fail, unless the backlash is set too close or no backlash at all.

03-17-2019, 06:24 PM	#41
larrys40 Senior Member Join Date: May 2010 Location: St Charles , Missouri Posts: 1,998	Re: Move Pinion forward and back per Les Andrews I agree with tom on his assessment. I have also torn down and rebuilt more than a couple hundred myself, i have two to do this week ... and have also never seen nor have ever had the call to use pinion shims. I agree that a carrier shim to move the ring gear closer is the solution. I’ve also never removed any original ones of those either. Are there anomolies,sure. But my bet is that the normal process will correct it with proper installed and parts to spec. I do start with a.010 gasket on each side and find that’s generally close to the norm. I do think it’s important to use Timken bearings and races as they are of a know quality and dimension. Good luck Larry shepard

03-17-2019, 11:57 PM	#42
steve hackel Senior Member Join Date: May 2010 Location: midlothian illinois Posts: 447	Re: Move Pinion forward and back per Les Andrews Hello to all; "please" excuse the origin of my question, but with 41 posts and so many different opinions on the subject of shimming the pinion - can one of you post a picture or at least a sketch of how and where you are installing the shims to move the pinion into or away from contact with the ring gear teeth? I am "SO" confused...… Steve

03-18-2019, 12:42 AM	#43
redmodelt Senior Member Join Date: May 2010 Location: Portland OR Posts: 6,342	Re: Move Pinion forward and back per Les Andrews You pull off the bearing on the carrier and add a shim behind it, or as I do behind the cup in the axle tube. __________________ I know the voices aren't real but damn they have some good ideas!

03-18-2019, 10:34 AM	#46
redmodelt Senior Member Join Date: May 2010 Location: Portland OR Posts: 6,342	Re: Move Pinion forward and back per Les Andrews Sponsored Links (Register now to hide all advertisements) Thank you Tom and Dave. I get it and understand. __________________ I know the voices aren't real but damn they have some good ideas!

03-18-2019, 12:33 PM	#47
steve hackel Senior Member Join Date: May 2010 Location: midlothian illinois Posts: 447	Re: Move Pinion forward and back per Les Andrews Thanks for all the help and pictures : its just another weapon in the arsonal of tools and techniques needed to do the job the right way the first time!

03-18-2019, 03:45 PM	#48
denniskliesen Senior Member Join Date: Nov 2016 Location: SoCal Posts: 877	Re: Move Pinion forward and back per Les Andrews Model A differentials aren't as critical as far as gear mesh, compared to modern and high pressure use. My past experience with differentials has been Construction Equipment. You better make sure if working on one know what you are doing and do it properly, no guess work. Generally the depth of the pinion gear in relation to the ring gear is referred to as cone center. Dave in MN touches on this in his post #45 as saying the pinion is basically cone shaped. To get an accurate cone center means if you knew where the point of the cone is, then that point would be in relation to the center of the ring gear. That is where the pinion depth would need to be. Aftermarket gears and industrial applications have these numbers scribed on the gear set. They usually sell the tools to set and or measure the pinion depth for their gear sets if they are marked. Otherwise you need to be able to check tooth contact pattern. You don't mismatch those gear sets. Most people will say it's not that critical to know what the backlash is precisely. I have never read or been told who does or has the tool to precisely measure backlash between ring and pinion. Finger feel is not good enough for me. Therefore I made tools to take the guess work or finger feel out of the equation. Granted I have not done hundreds of Model A differentials I have never had a Model A differential fail that I worked on. And I have the tools to accurately measure backlash. But seldom does a Model A ring and pinion that I have been told or read about fail, unless the backlash is set too close or no backlash at all.