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Old 11-20-2019, 01:19 PM   #1
Russ/40
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Default Clutch chatter project results

Some time ago I explained my difficulties with clutch chatter, and as I left it last, I was going to add some support to the rear of the '39 transmission.

I picked up a rear Float a Motor mount from Mikes attic sale real cheep. It is the Aluminum version. I used rubber I had on hand and sculpted a cushion to fit between the mount and the lip of the center cross member. The mount was designed for a Model A clam shell, which is 3/8" wider than the V8 clam-shell. I was able to remove material from each side of the V8 clam-shell by elongating the bolt holes. As to location for and aft, the mount was to far posterior which caused interference between the steel top plate of the mount, as well as the aluminum portion. I removed ample material to assure the mount would not scrub metal to metal. Adequate cushion contact has stabilized the rear of the heavier V8 transmission. There is a general feeling of stability now from below which makes the A feel more solid in the seat of your pants. Clutch chatter has almost totally disappeared. It has increased the pleasure quotient a lot and I'm enjoying the ride more than ever. I'm very pleased with the result.

Some pictures below:
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Old 11-20-2019, 01:33 PM   #2
ryanheacox
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Default Re: Clutch chatter project results

Russ, I can't remember, did you have float a motor mounts installed? Either way, glad to hear that rear mount worked out for you.

Also, I really like that battery hold down. Is it available somewhere or was it custom made?
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Old 11-20-2019, 02:01 PM   #3
Russ/40
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Default Re: Clutch chatter project results

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Originally Posted by ryanheacox View Post
Russ, I can't remember, did you have float a motor mounts installed? Either way, glad to hear that rear mount worked out for you.

Also, I really like that battery hold down. Is it available somewhere or was it custom made?
Ryan, No I have stock engine mounts front and rear. Ever since I put the '39 transmission in I have had thoughts that more support there cant be a bad thing and probably would render positive results. I have also come to believe, the condition of the clam-shell can be a factor in smooth clutching. I have been searching for a NOS clam-shell set to test this theory, as the one I used for this change has significant wear.
The battery hold-down I made myself, after finding no other I was satisfied with. Of course it is fitted to a group-1 battery size which is stock. Battery is solidly mounted, and fully accessible. I suppose I could start making them, as a jig to make them would be simple to fab up.
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Old 11-20-2019, 07:30 PM   #4
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Default Re: Clutch chatter project results

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Originally Posted by ryanheacox View Post
Also, I really like that battery hold down. Is it available somewhere or was it custom made?
I agree. Nice job "thinking outside the box" on the battery hold down. I have a 12v battery and it is hard to find a hold down that fits the battery and works with the original box. Yours would work great (with a little modification) and relatively easy to fab.

Nice work on the FAM rear mount.
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Old 11-20-2019, 10:35 PM   #5
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Default Re: Clutch chatter project results

Anyone know for sure how the FAM trans mount relates to clutch chatter ? Could unsupported trans weight actually warp the bell housing and cause clutch misalignment ?
Strange that NOS engine mounts do not have the same clutch chatter issue since the trans is completely unsupported.
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Old 11-21-2019, 12:08 AM   #6
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Default Re: Clutch chatter project results

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Quote:
Originally Posted by Mulletwagon View Post
Strange that NOS engine mounts do not have the same clutch chatter issue since the trans is completely unsupported.
I believe Russ stated he did have stock mounts.
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Old 11-21-2019, 02:35 AM   #7
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Default Re: Clutch chatter project results

Very nicely done Russ. I resculpted an aluminium FAM centre mount to fit with a RHD Mitchell gearchange. Engine supported on rubber FAM at front and rear. All was well until one day clutch judder started. I found both vertical bolts had broken their aluminium threaded posts off the main centre support bracket. Once all welded back with plenty of extra surrounding aluminium, all has been well for many thousands of miles.
But it certainly shows that centre support is a good thing to have, in your and my cases at least. There are some who don't use it and have no problems according to past posts here. But I keep a good eye on mine now in case it breaks again. The cast iron ones must be stronger I guess.
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Old 11-21-2019, 11:54 AM   #8
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Default Re: Clutch chatter project results

What does the steel plate on top of the FAM mount actually do? It looks like it just sits there.
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Old 11-21-2019, 12:31 PM   #9
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Default Re: Clutch chatter project results

It helps provide a trap for the rubber cushion, creating an enclosed space.
It could have been designed differently, especially with the iron version of the mount.
The aluminum version is probably strengthened by it.
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Old 11-21-2019, 12:46 PM   #10
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Default Re: Clutch chatter project results

The steel plate rests on top of the rubber block . The rubber block slightly raises the rear of the transmission and cushions out the chatter .

Some that don't use the center support and have no clutch chatter probably ride the clutch pedal a bit more . The model A isn't a perfect creation .i
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Old 11-21-2019, 02:14 PM   #11
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Default Re: Clutch chatter project results

I wonder if some home made anti-chatter rods (like in the later 4's and V8's) would help/eliminate the chatter you've experienced??
Paul in CT
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Old 11-21-2019, 05:20 PM   #12
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Default Re: Clutch chatter project results

This has been an interesting read. I have an aluminum FAM kit. Might install the clam shell piece and see if there is any difference. Will be interested to hear your findings with a NOS clam shell when you find one.
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Old 11-22-2019, 11:19 AM   #13
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Default Re: Clutch chatter project results

Quote:
It helps provide a trap for the rubber cushion, creating an enclosed space.
Got it, thanks.
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Old 11-23-2019, 10:51 AM   #14
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Default Re: Clutch chatter project results

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Originally Posted by 1931 flamingo View Post
I wonder if some home made anti-chatter rods (like in the later 4's and V8's) would help/eliminate the chatter you've experienced??
Paul in CT


Anti-chatter rods would help some in removing side to side chatter but wouldn't help up and down chatter .

The chatter problem listed above was mostly caused by the heavier 39 transmission and the unsupported length-distance between the engine and the universal joint . Just my thought .
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Old 11-23-2019, 11:24 AM   #15
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Default Re: Clutch chatter project results

Purdy, I never considered side to side chatter to even be a possibility. To my thinking, chatter is a longitudinal issue, and antichatter rods set that distance fast. As longitudinal distance changes, it has a tendency to raise and lower the drineline at the clamshell. I may be tottaly off base as it is impossible to visually witness it. A go-pro camera strategically placed could answer the question - i don't have one unfortunately. Hence, my consideration of a best possible clamshell fitment to test the theory. I attribute my recent significant improvement to the driveline movement being dampened by the added FM cusion.
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Old 11-24-2019, 11:37 AM   #16
Purdy Swoft
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Default Re: Clutch chatter project results

The later V8 models used anti chatter rods to stabilize the floating motor mounts . Model A's didn't use floating motor mounts . Because of the more solid rear motor mounts , the model A motor and transmission was mounted in a more stable manner . In other words if the engine and transmission slightly jumps about when taking off , you get chatter . The reason this problem is referred to as clutch chatter is because as the clutch pedal is released is when the chatter occurs .
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Old 11-25-2019, 12:21 PM   #17
Purdy Swoft
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Default Re: Clutch chatter project results

My thoughts on the anti chatter rods used on the V8 is That there is one anti chatter rod on each side at the rear of the engine . When floating motor mounts are used without anti chatter rods , the engine can slightly move backwards and then forward on each side of the rear of the engine and transmission and cause jerking or chatter when the clutch pedal is released .The anti chatter rods hold the rear of the engine firmly and removes any backward or forward movement . In other words my thought is that if the engine slightly chattered forward or backward on one side it would move at a slight side to side movement . The anti chatter rods are mounted on both sides and prevent slight angled side to side chatter . The rear transmission mount that users the rubber block at the clam shell , slightly raises and cushions out any up or down movement or chatter . My thoughts are if floating motor mounts are used without the rear mount and rubber block , there will be clutch chatter when releasing the clutch pedal .

Another thought is if the frame is slightly sagged at the rear motor mounts the floating rear mount at the transmission alone will raise the torque tube so that it doesn't drag on the service brake cross shaft .
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Old 11-25-2019, 01:21 PM   #18
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Default Re: Clutch chatter project results

Purdy, wouldn't it be tough to try and validate either of our two theorys? A slip joint in the driveline would probably solve the whole problem.
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Old 11-25-2019, 02:31 PM   #19
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Default Re: Clutch chatter project results

Well , I can't see or take a picture of the chattering parts while driving the model A . If it is chattering , this is just my thought . I feel that the unsupported distance between the engine and the universal joint plays a big part . Some of the later V8 Fords had mounting ears at the back of the transmission case that helped , at least the 37 Ford pickup did .
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