Transmission noise (still!)

JohninKuranda

JohninKuranda

Senior Member
My New Years resolution for 2026 is simply to solve the ongoing issue of the transmission noise of my 1928 35A Model A.

I have jacked up the rear end and removed the transmission 4 times (at least) over the past few years – so much so that I have the process down pat! But the noise still persists. So, before I start the process yet again, I want to pick the barn’s collective brains once more.

The noise is more properly best described as a “whine”. With the engine idling, in reverse and first gear, the pitch of the whine is at its highest. In second gear, the pitch is lower. In third gear, it is lower still. When I push my foot down on the clutch pedal the noise disappears. In neutral, with foot off the clutch pedal, the whine is still there.

When I increase the engines acceleration; in reverse, first and second gears, the pitch increases to higher levels proportionate to the speed of the engine. In third gear, there is very little change in the pitch or overall loudness.

Over the past few years, I have replaced ALL the gears including the main drive gear, cluster gear and reverse idler. I have also replaced the main drive gear ball bearing and main drive bearing. All these have been purchased from Australian suppliers, sourced from reputable USA wholesalers (such as Snyders).

I have read basically every transmission noise post and response on the forum today – what a way to spend much of New Years Day! I have also noted the various comments about the speedometer cable and have removed that – no change. Previously I checked that the starter motor bolts were not causing an obstruction – they were not.

Car background information. This Model A was built with a multi-disk clutch. I live in the humid tropics and it was always clogging up. I changed it several years ago. This meant a replacement flywheel machined down for an early V8 clutch plate. Also, there was a replacement flywheel housing and transmission case. The throw-out bearing has also been replaced.

I have also previously boxed up the transmission case and the gears and shipped the packed several thousands of miles to a specialty Model A and T workshop for them to inspect. All okay. At the time of replacing the clutch, I also installed a “Float-A-Motor” kit.

So, due to the newness of the parts, I do not believe it’s a gear issue. I am left thinking it could be the pilot bearing or the cluster gear bearings. Or perhaps there has been a slight change to the levels of the drive train due to the “Float-A-Motor”?

I would welcome ANY suggestions or thoughts on how to reduce the noise. I get that there will always be some noise (particularly in second gear), but currently the noise/whine is at the point where I feel embarrassed to drive the car. Which is not the space I would to be in.

I would appreciate your thoughts, and a very Happy New Year to you all.

John
 
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Straight cut gears are "always" noisy. Third gear won't be as noisy because the power is a straight shot through the trans in third. I don't know how noisy your trans is but Model A's are definitely noisy in first and second. Check out some YouTube videos and see how noisy your Model A is compared to others. The whine is part of the vintage experience.
 
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Has it been noisy like this since the very first day you owned it, or gradually get louder as you've owned it? Or was there an event, something that was repaired or replaced, and the noise started after that?
 
Was it quiet before the modifications and switch over to the V8 clutch?
Have any of the three caged roller bearings been replaced? Those are known to cause a whine if going bad.
If you do pull it out again I would suggest going ahead and replacing the pilot bearing.
Check the tightness of your float a motor mounts. Perhaps they are tightened too much. I'm not real up to speed on those but if I understand correctly on them the rear two mounting bolts just need to be tightened enough to just start squeezing the rubber mounts.
When using the float a motors some have gone back to the original front motor mount while still using the floaters in the rear and some have removed them altogether and gone back to the original style to alleviate various troubles.

I've often found that float a motor mounts and modern points are two "upgrades" that can sometimes cause trouble for folks.
 
It could be the pilot bearing, or alignment between the transmission and the engine. This is not a fix but you may want to experiment with thicker transmission oil. Try the modern 90W-140 grade 5 gear oil or some thicker stuff if you can find it. Some people have used STP, straight or mixed with gear oil.
 
Some people have used STP, straight or mixed with gear oil
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(Raises hand) Straight STP out of the peal top container here.

Yeah. I know its not a lubricant. Tell that to the transmission.

When I first got the Avatar, my Dad was surprised at how easy it shifted, and how little noise it made.

On rebuilding I found the prior owner had used SAWDUST in with whatever oil he had used. Frankly, even with the STP, I've never been able to bring it back to that same degree of functionality.

Tractor Supply sells 50lb bales of sawdust. $7.99

This latter offered in good fun.

Joe K
 
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TMarsh said:
Sounds like pilot bearing to me.
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Tending to agree. And - allied to the same bearing, that "extension" on the pilot/input shaft to the ******.

I've bushed the extension and turned it using a lathe to a "drive-on" fit with the bearing. You want the shaft to turn supported and centered by the bearing. Some "knurl" the extension to achieve the same result.

Joe K
 
The pilot bearing is only in play when your foot is on the clutch pedal.When the clutch is engaged,the shaft,disc,pilot bearing and flywheel are one piece.The only time the pilot spins while in gear is when you step on the pedal.
any noise while rolling in gear is not from the pilot.The pilot will make noise when the pedal is depressed,and should go away when you let up.
 
Keith True said:
The pilot bearing is only in play when your foot is on the clutch pedal.When the clutch is engaged,the shaft,disc,pilot bearing and flywheel are one piece.The only time the pilot spins while in gear is when you step on the pedal.
any noise while rolling in gear is not from the pilot.The pilot will make noise when the pedal is depressed,and should go away when you let up.
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I think you are confusing "Pilot bearing" with "Throw-out bearing". The pilot bearing is in the flywheel and hold up the end of the main shaft. The Throw-out bearing is what contacts the pressure plate when you depress the clutch pedal.
 
Transmission noise can be misdiagnosed noise originating from the differential. The sound from the rear end can easily transmit up the torque tube and sound like it's coming from the ******. I know first hand. I thought I had a groaning transmission in my Model T until one day the rear end let go.
 
I'm not confusing the two.When the clutch is depressed,the shaft stops turning,and the pilot bearing starts turning.The flywheel is turning,and the shaft and disc is staying still.The pilot is turning at that point.Let up on the clutch,the flywheel,disc,shaft,and all become one big rotating mass.Pilot bearing does not spin when the clutch is engaged.
 
Guy’s, I think the only part that seems to not having been replaced is the pilot bearing.

Whenever I replace or remove the clutch, I always replace both the pilot and throw out bearing .

At this point, if this was my car. That’s what I would do. Replace the pilot bearing.

Happy New Year.
 
Keith True said:
I'm not confusing the two.When the clutch is depressed,the shaft stops turning,and the pilot bearing starts turning.The flywheel is turning,and the shaft and disc is staying still.The pilot is turning at that point.Let up on the clutch,the flywheel,disc,shaft,and all become one big rotating mass.Pilot bearing does not spin when the clutch is engaged.
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Gotcha. I always use a bronze bushing type pilot bearing, don't make noise.
 
Driveline noise can travel long distances from the cooling fan to the rearend ! It would be helpful to hear audio and video with the floor boards removed . The other day I had the clutch cover off watching it working, deciding it was fine but just noisy, reinstalled the cover and was very quiet . With the wheels off the ground car running in gear crawl around with a stethoscope check for the noise. Start removing possible causes of noise like fan belt on the engine and whatever else , lastly remove the rearend and run the car in gear .

Mobile steam cylinder oil 600W will quiet down bearings and gears !!!!!
 
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