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Old 05-09-2019, 03:19 PM   #1
cobra5laddict
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Default Help with a noisy Banjo rear end.

I have a 37 or 38 banjo rear in my 28 roadster with a closed drive / 39 trans. Everything is hearsay because i bought this car unfinished. The P.O simply stated that he installed a matched set 3.54 ring and pinion in the rear. The ratio appears correct not that it has anything to do with the howl I am experiencing. The rear is quiet under acceleration (running 140w gear oil). It howls under deceleration. The howl is the loudest when i fully let off and the engine is slowing the car to a stop sign. any speed from 20-30 mph on up howls) Up until now i've been shifting to neutral when slowing to keep things quieter (it still howls slightly but better).
Does anyone have any suggestions to look at first before i pull the rear out? Not that i have anything to go off of, but i'm doubting that this noise only on deceleration is because of incorrect gear mesh. im wondering if what i am hearing is the pinion walking in and out of the housing. I looked at a few diagrams and i'm thinking perhaps the jamb nuts on the pinion are not adjusted correctly or maybe loose?
I'm also new to closed drive units so i'm assuming that the torque tube would stay attached to the trans and i would unbolt the tube from the housing and disassemble that way, thoughts?
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Old 05-09-2019, 04:07 PM   #2
Ken/Alabama
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Default Re: Help with a noisy Banjo rear end.

Could be the pinion nuts are loose letting the pinion walk in and out. Could have incorrect amount of backlash , that's achieved by using different gasket thickness from side to side between the axle housings and center section. Either way your gonna have to take it apart.It all comes out as a unit, torque tube and all after its unbolted from the transmission. Just I bolting the torque tube won't do it cause the driveshaft is pinned to the pinion and has a bearing,seal and snap ring at the top end.
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Old 05-10-2019, 03:58 AM   #3
Mart
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Default Re: Help with a noisy Banjo rear end.

Yeah, agree with above. Pull the rear and check the big pinion nuts. They have to be at a certain tightness so that the pinion rotates with a certain drag, but then the two nuts need to be locked together tightly and locked with the special tab washer. Doing those nuts up tightly is difficult if you do not have the correct sized slim wrench needed to hold the inner nut.

The helix angle of the gear teeth will pull the pinion into tighter mesh on the overrun.

It needs to be addressed sooner rather than later as abnormal wear will occur if left to run in this condition.

Mart.
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Old 05-10-2019, 05:30 AM   #4
35ragtop
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Default Re: Help with a noisy Banjo rear end.

Hi guys,
Lawrie recently posted a story on here how he put a new set of 354 gears in a banjo and that it needed a .30 thou shim on the pinion to get the correct mesh. Now this observation by Lawrie sent shivers down the spines of us shadetree mechanics who had built these diffs only addressing pinion preload and backlash and and ring preload. Bugger !
I have built diffs that ended up whining because of mismatched or mis meshed gears. If the noise upsets you ,pull it down and do it all again ,check the mesh with bearing blue or whatever. I think that Lawrie was onto something ( check his posts on this). I have been lucky with new gear sets, but yours may have this .30 mesh issue.
regards Dave h
shadetree mech
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Old 05-10-2019, 07:06 AM   #5
JM 35 Sedan
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Default Re: Help with a noisy Banjo rear end.

Not likely that anything can be done to fix that rear as bolted in place. I'd suggest you begin removing the rear and disassemble. If you don't feel comfortable doing the repair, find someone who can do this repair for you. You don't have your approximate location listed in your avatar, so no recommendations can be given for someone to do this repair for you.
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Last edited by JM 35 Sedan; 05-10-2019 at 07:36 PM.
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Old 05-10-2019, 01:42 PM   #6
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Default Re: Help with a noisy Banjo rear end.

Thank you for the feedback. I will update my location but im in Denver CO
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Old 05-11-2019, 10:50 AM   #7
TJ
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Default Re: Help with a noisy Banjo rear end.

Quote:
Originally Posted by cobra5laddict View Post
Thank you for the feedback. I will update my location but im in Denver CO
If you are in Denver contact Bert's Model A Shop. Somebody there will know who can help on the rear end.
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Old 05-11-2019, 03:24 PM   #8
Flathead Fever
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Default 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.
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Old 05-12-2019, 08:18 AM   #9
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Default Re: Help with a noisy Banjo rear end.

Thank you for the in depth explanation on setup! I did talk to Tim at Berts llast month when I was in. I explained what I was hearing and asked if they could work on it. They mentioned that the later v8 banjo was a tad different than the A’s. Their tech would rather not take it on. I understand, not faulting them. They did give me a number for a guy they call aussie Steve. I am going to try and give him a call and see if he can look at it. It’s prime roadster weather so I’m hoping it won’t be down too long.
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Old 05-12-2019, 06:57 PM   #10
Flathead Fever
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Default Re: Help with a noisy Banjo rear end.

The only difference is the Model A and early '32 have a tapered driveshaft with a key way in the pinion gear. Plus the later rear ends have the extra straddle mounted bearing on the end of the pinion which is a stronger setup. Setting up the gear pattern, backlash and pre-load are done exactly the same way. If you cannot set a later rear end up properly you can't do the earlier ones either.

I rather rebuild the later ones. After the battle I had getting a tapered '32 driveshaft out of the '32 pinion gear. A soaking in penetrating oil, a hydraulic press and heat from a rose bud torch would not break that tapered fit a part. I eventually destroyed the end of the driveshaft pressing on it. I should have just torched the gear off or split the gear with a grinder.
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Old 05-12-2019, 09:15 PM   #11
alanwoodieman
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Default Re: Help with a noisy Banjo rear end.

1941 pick up with 3:78 rear gears, had an unusual noise in rear end, owner thought it was trans but could not be convinced it was not. changed trans, noise was still there, turned out the pin in the sleeve coupler on drive shaft had broken and a piece of it became wedged between torque tube and pinion nut and when he backed up it spun the pinion nuts off the pinion. it was the weirdest thing I have seen in over 46 years or working on these Ford!
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