| Johns46coupe | -- 10-21-2010 @ 12:36 AM |
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Installed a new clutch, pressure plate, TO and pilot bearings and had the pressure plate balanced with the flywheel after resurfacing the flywheel. Also replaced both front and the rear motor mounts. New clutch works fine except for a very slight occasional chatter. Problem is a deep noise and vibration that occur when the engine is revved up from idle. It's not steady, comes and goes repetitively depending on RPMs. I would say it repeats about once every second around 1500 or so RPM's. It happens in neutral, stopped, in my driveway. Happens whether the clutch is engaged or not. Also happens when the car is driven. Definitely tied to RPM's. Seems like a harmonic type of issue. I've removed both belts and it still happens. Don't see anything touching the frame or wobbling, etc. I'm wondering if it has something to do with the motor mounts and the alignment of the engine and trans. Is there a way to make sure that everything is lined up correctly and in the optimum position on the mounts? This noise and vibration did NOT exist until I did the clutch job. Any help or ideas would be appreciated. John
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| 40 Coupe | -- 10-21-2010 @ 5:10 AM |
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if you do not have the anti chatter rods installed, install them and tighten the engine side nuts. This will hold the engine rearward when the clutch is depressed. there should be no clutch chatter.
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| supereal | -- 10-21-2010 @ 9:07 AM |
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As the periodic vibration didn't appear until you replaced the clutch, It is more than likely the source of the problem. It could be an out-of-balance pressure plate, or one that was bent by not gradually cinching down the mounting bolts, which can bend the plate housing. The clutch disk may have an off center hub. This will create a vibration when it is gripped by the pressure plate, shaking the engine. Many repro parts are suspect, and you may have poor examples. The transmission housing may not be flat against the bell housing if the mounting dowels didn't match the holes. As for clutch chatter, it is characteristic of most old Fords. The anti-chatter rods were tried, and later discarded as an effective "fix". I've had some chatter in all of my old Fords, and I learned to start off in second gear when the low gear power wasn't necessary.
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| TomO | -- 10-21-2010 @ 9:08 AM |
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Did you check the flywheel for run-out after re-installing it. You could have debris on the mounting flange. The engine radius rods were not installed on the 46 cars at the factory and they run from the back of the block to the front cross-menber when installed. It is difficult to alter the alignment of the engine to the transmission and the motor mounts. You could loosen the mount bolts and work the clutch while running the engine to see if that affects the vibration. I would start with a cylinder balance test. Hook up your vacuum gauge and short out the spark plugs one at a time. Watch the vacuum gauge, you should have the same drop as each plug is shorted to ground. Tom
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| Johns46coupe | -- 10-21-2010 @ 9:38 AM |
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Thanks for the replies. The flywheel was checked for runout before it was balanced, then the pressure plate was bolted on in gradually, then the two were balanced together. I cinched the pressure plate gradually and torqued for the final. The chatter is so slight I'm not really worried about it. It's the noise and vibration that I'd like to eliminate. The vibration is slight and of a harmonic nature that increases as RPM's go up. Get's very noticeable at speed but also does it when stopped in neutral regardless of clutch in or out. Did not check runout after flywheel install. I could have a piece of dirt in there but I was very careful to clean the flywheel and the crank. I will do the cylinder balance Tom suggests. How tight should motor mount bolts be, especially the rear one? John
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| TomO | -- 10-22-2010 @ 8:39 AM |
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Tighten the motor mounts until the rubber just starts to compress and then line up the cotter pin hole by tightening more. I agree with Supereal that the source of the vibration is in the clutch, pressure plate or flywheel. There are a lot of sources for rebuilt clutches and pressure plates that do not know what they are doing. They are used to the modern type clutch assemblies. Fort Wayne Clutch has a good reputation. The cylinder balance test will find a cylinder that is not firing all of the time and causing vibration, but that vibration usually shows up at a specific RPM and continues through any higher RPM. Tom
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| supereal | -- 10-22-2010 @ 9:28 AM |
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The revised rear motor mounts for the late 40's Fords didn't appreciably reduce the annoying clutch chatter. The problem is made worse by worn rear spring shackles and/or a weak spring. The Ford configuration of the torque tube rear suspension was continued from the earliest Model T's thru the '48s, when the Hotchkiss system came out in the '49s. The motor mounts in the early type bear the "push" of the rear axle, and the movement is amplified by the clutch linkage. As horsepower increased, so did the chatter. I suspect that the clutch disk hub is off center on your car by a very small amount. We used to reduce out of line problems by loosening the transmission housing to engine bolts and, while the rear axle was suspended on a hoist or jack, running the drive line while retightening the bolts. This allows the pieces to self adjust enough to reduce vibration caused by nonalignment. Just be very careful about crawling under a running car unless it is really secure.
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| 40guy | -- 10-22-2010 @ 2:46 PM |
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This may sound foolish but it happened to me one time. I had a similar noise and noticed the nut that holds the fan to the crankshaft had worked loose. when the centrifugal force of the engine reving would spin the fan forward. I could see where it had been skimming the radiator. Fortunately I caught it in time before any damage was done.
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| Johns46coupe | -- 11-19-2010 @ 11:49 PM |
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Thank you very much gentlemen. Per Super's advice, I loosened the bolts holding the transmission to the motor after putting the back of the car on jack stands. Also loosened the motor mounts. Ran the motor in gear at about 1500 RPM and gradually tightened the transmission bolts to engine by taking each bolt up a little until all were tight and torqued. Then I tightened the motor mounts per TomO. This eliminated the clutch chatter I had but not the vibration of the motor. After a lot of head scratching, I removed the fan belt from the fan (left the other belt on) and the vibration was GONE! I took the fan hub apart and found a fair amount of play between the shaft and the sleeve (I think that's what it's called). Any ways, I now have a fan assembly from an 8 BA motor on (ball bearing I think) and there is no vibration. Not sure if the new fan is the way to go though. It looks a little different and fan blades are shaped differently. Opinions? Thanks again to all who responded! John
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| supereal | -- 11-20-2010 @ 5:19 AM |
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John: The oil reservoir fan hub has always been a weak spot. While the decal still lists "engine oil" as the preferred lube to fill it, 80-90 transmission oil should be used. To be sure the reservoir is filled correctly, remove the filler screw and when the hub won't hold any more oil, with the srew still out, turn the filler hole to the down position and allow the excess oil to drain. Then, replace the filler screw. The fan hub doesn't have any real bushing or bearing, but parts are still available. After going thru several hubs, I decided to "improve" the one on my '47, and made a ball bearing version in our shop. Now, no more hearing the hub squeal when I am on the road. I'm glad the transmission centering trick worked for you. It usually doesn't remove all the chatter, but does reduce it enough to give significant improvement.
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