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Flathead Fever · 05-11-2019, 03:24 PM

I built at least 100 rear ends in my 30-years as a fleet mechanic. On rear-ends you have a drive-side gear pattern setup and a coast-side pattern setup. You attempt to center both sides but its not always possible do to machining differences. Sometimes its a compromise, The drive-side will be set perfect and the coast side might be too deep or way out at the edge of the teeth. You go back and change the drive-side pattern to move the coast side pattern away from the inside or outside edge to prevent noise which is basically the gears chewing each other up. You do this by changing the backlash (moving the ring gear in closer of further away). On an Early Fords this means moving paper shims from one axle housing to the other housing while still maintaining the proper pinion bearing pre-load and staying within the recommended backlash allowances. The other way to change the pattern is to move the pinion gear in or out. Were talking just a little, the thickness of a piece of paper makes quite a difference in the pattern. There were no pinion depth adjustments to change the pattern on Early Fords. That meant the Ford machining had to be perfect on the center section, the axle housings and the gears. Modern cars (1960s to 2000) were not machined that accurate so they use pinion depth gauges to measure the pinons location in the housing and then adjust it by adding shims. 1960s Ford shop manuals have excellent pictures of the different acceptable patterns. The pattern does not need to be perfect on both the drive and coast sides but they need fall into an acceptable range. Depending on which side is off and if its too deep or too shallow the manual tells you if you should take away shims, add shims, increase the backlash or decrease it.

Under acceleration the power is transmitted through the drive-side contact patch. That is where the pinion gear is applying the rotational force to the ring gear. If you apply a gear marking compound ( I get mine from the GM dealer, it worked the best) the pressure between the gears squeezes the compound out and shows you where the gears are making contact. That is while rotating the pinion in the forward direction. Under deceleration the rear wheels are rotating the ring gear so the the ring gear is driving the pinion gear. If its noisy while decelerating the pattern on the coast-side is not correct, the gears are worn or the gears were machined poorly which should have been spotted when the pattern was checked. Its not easy to get a good pattern just by rotating the gears. There needs to be resistance applied to one gear or the other. On the trucks I worked on we would wrap a rag around the pinion and have somebody pull on it while somebody rotated the ring gear on one of the bolts with a wrench. Or somebody would turn the pinion gear while some dragged something against the ring gear to create some resistance. Or I would put the brake drums back on and set the parking brake so the would drag a little creating resistance between the ring gear and pinion. By doing this it would create a nice clean pattern on the gears. Without the extra resistance it was more of a smeared pattern that was not as defined.

The problem with an Early Ford is you do not have access to the gears to see the pattern like you do on lets say a 9-inch Ford rear end. You will probably need to pull axle housing off, slide the gear out, change things. Put it back together with more gear marking compound. Take it a part again, move things around. Put back together and just keep making adjustments until you achieve the best pattern possible.

On later rear ends you have a front pinion bearing on the front side of the housing and rear pinion bearing on the backside. Some places will tell you that under acceleration a front bearing could make noise and on decelerating a rear bearing could make noise. I never had that happen. When a Pinion bearing went bad it made noise all the time. That does not mean that it does not happen.

The last thing would be the pinion bearing pre load being too loose and allowing the pinion gear to move. Your going to need to tear it a part, but check things before you start ripping it a part. Check for any play in the pinion bearings. Check the backlash measurement. Check the side bearing preload to make sure the ring gear is not moving.

I would have serious doubts about the home enthusiast attempting to setup a rear end that had never done one before without some help doing their first one. They need to have an inch-pound torque wrench, a dial indicator, a hydraulic press, gear marking compound and a lot of patience. There is no original literature on gear patterns on an early Fords. When you start using aftermarket gears you need to know what patterns to look for. You might need to improvise and add pinion shims which never existed on the original rear ends. If you do take it a part try to salvage the axle housing gaskets and don't mix up the two sides so you can measure them with a micrometer (another tool you need) These are your shims

The old timers told me on the Model Ts they set the rear-ends up with a business card. If it went between the ring and pinion snugly it was good. If it tore the card the backlash was too tight.

05-11-2019, 03:24 PM	#8
Flathead Fever Senior Member Join Date: May 2010 Location: Yucaipa, CA Posts: 1,093	Re: Help with a noisy Banjo rear end. I built at least 100 rear ends in my 30-years as a fleet mechanic. On rear-ends you have a drive-side gear pattern setup and a coast-side pattern setup. You attempt to center both sides but its not always possible do to machining differences. Sometimes its a compromise, The drive-side will be set perfect and the coast side might be too deep or way out at the edge of the teeth. You go back and change the drive-side pattern to move the coast side pattern away from the inside or outside edge to prevent noise which is basically the gears chewing each other up. You do this by changing the backlash (moving the ring gear in closer of further away). On an Early Fords this means moving paper shims from one axle housing to the other housing while still maintaining the proper pinion bearing pre-load and staying within the recommended backlash allowances. The other way to change the pattern is to move the pinion gear in or out. Were talking just a little, the thickness of a piece of paper makes quite a difference in the pattern. There were no pinion depth adjustments to change the pattern on Early Fords. That meant the Ford machining had to be perfect on the center section, the axle housings and the gears. Modern cars (1960s to 2000) were not machined that accurate so they use pinion depth gauges to measure the pinons location in the housing and then adjust it by adding shims. 1960s Ford shop manuals have excellent pictures of the different acceptable patterns. The pattern does not need to be perfect on both the drive and coast sides but they need fall into an acceptable range. Depending on which side is off and if its too deep or too shallow the manual tells you if you should take away shims, add shims, increase the backlash or decrease it. Under acceleration the power is transmitted through the drive-side contact patch. That is where the pinion gear is applying the rotational force to the ring gear. If you apply a gear marking compound ( I get mine from the GM dealer, it worked the best) the pressure between the gears squeezes the compound out and shows you where the gears are making contact. That is while rotating the pinion in the forward direction. Under deceleration the rear wheels are rotating the ring gear so the the ring gear is driving the pinion gear. If its noisy while decelerating the pattern on the coast-side is not correct, the gears are worn or the gears were machined poorly which should have been spotted when the pattern was checked. Its not easy to get a good pattern just by rotating the gears. There needs to be resistance applied to one gear or the other. On the trucks I worked on we would wrap a rag around the pinion and have somebody pull on it while somebody rotated the ring gear on one of the bolts with a wrench. Or somebody would turn the pinion gear while some dragged something against the ring gear to create some resistance. Or I would put the brake drums back on and set the parking brake so the would drag a little creating resistance between the ring gear and pinion. By doing this it would create a nice clean pattern on the gears. Without the extra resistance it was more of a smeared pattern that was not as defined. The problem with an Early Ford is you do not have access to the gears to see the pattern like you do on lets say a 9-inch Ford rear end. You will probably need to pull axle housing off, slide the gear out, change things. Put it back together with more gear marking compound. Take it a part again, move things around. Put back together and just keep making adjustments until you achieve the best pattern possible. On later rear ends you have a front pinion bearing on the front side of the housing and rear pinion bearing on the backside. Some places will tell you that under acceleration a front bearing could make noise and on decelerating a rear bearing could make noise. I never had that happen. When a Pinion bearing went bad it made noise all the time. That does not mean that it does not happen. The last thing would be the pinion bearing pre load being too loose and allowing the pinion gear to move. Your going to need to tear it a part, but check things before you start ripping it a part. Check for any play in the pinion bearings. Check the backlash measurement. Check the side bearing preload to make sure the ring gear is not moving. I would have serious doubts about the home enthusiast attempting to setup a rear end that had never done one before without some help doing their first one. They need to have an inch-pound torque wrench, a dial indicator, a hydraulic press, gear marking compound and a lot of patience. There is no original literature on gear patterns on an early Fords. When you start using aftermarket gears you need to know what patterns to look for. You might need to improvise and add pinion shims which never existed on the original rear ends. If you do take it a part try to salvage the axle housing gaskets and don't mix up the two sides so you can measure them with a micrometer (another tool you need) These are your shims The old timers told me on the Model Ts they set the rear-ends up with a business card. If it went between the ring and pinion snugly it was good. If it tore the card the backlash was too tight.