High speed vibration
Del Alspaw
I need some suggestions for what and where to look. My 29 tudor has a
vibration when it hits about 50 mph or when you reach top end rpm
between shifting. It seems to be in the drive train. She does not
knock or smoke or use oil (except for the rear seal). I have replaced
the fan and water pump. I went down a grade and popped her out of gear
and she coasted past 50 and was smooth as silk. She is all stock and I
never had the drivetrain apart since I have owned it. I was told the
tranny was fairly new when I bought her. Any ideas? Flywheel? Rods?
Crank? Some folks have told me its due to the solid rear engine
mounts. Does not seem to worse with time or anything just keeps me
from going over 50 and I suppose thats not all bad ... hahaha...
Thank you or time - Del
erics...@gforcecable.com
Vibration just at high speed, that's a new one for me.
Vibration all the time that's common.
I had an instance several years ago where I installed a
new V-8 clutch without balancing it and the flywheel. The
vibration occurred at all speed ranges and all RPMs (it
would not have gone away as it did in your test). It was
bad enough that after about 6 months I had a front fender
crack.
Also, don't forget about the differential. But that's
usually a noisey problem and not a significant vibration.
I remember chasing what everyone thought was a
transmission problem and it turned out I had chewed up a
pinion gear.
I don't feel like that's much help, but I will be
interested in what you find.
Thanks,
Eric Shogren
Shade Tree A's
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Lockwood, Fred C
Top end rpm. What happens if you are in neutral at the same engine speed.
Personally, I would suspect the prop shaft universal joint which is worn and troublesome under load but not coasting. Or the differential pinion bearing.
Others must have had similar experiences.
Fred
________________________________________
From: modelaf...@googlegroups.com [modelaf...@googlegroups.com] on behalf of Del Alspaw [dela...@gmail.com]
Sent: 07 January 2012 06:01
To: Model A Ford Forum
Subject: [ModelAFordForum:443] High speed vibration
--
Bentley Bohanan
really love a Model A that is smooth and quiet, what I call "A Pleasure to
Drive". They are not all like that unfortunately. I spend a lot of time
trying to figure out vibrations, so here are some things I would look for.
If you think about it, there are two types of vibrations, the kind you feel,
and the kind you hear. The ones you hear can be a bolt loose somewhere. You
said yours is one you can feel, so:
You did the right thing by getting the car up to speed, then pushing the
clutch and letting the engine speed drop, this has isolated the vibration to
the engine.
I would say if you have a vibration that is getting worse, then you need to
figure out what's going on. The original 2 blade fans are prone to crack at
the base of the blade, which will cause a vibration, and quickly fail,
taking out your hood or radiator in the process. I have had 4 blade fans
fail as well. You could try removing the belt and revving up the engine to
see if the vibration changes, that would isolate the fan and generator. I
wouldn't drive it like that. Just a quick check won't hurt anything.
Next, the pressure plate can be the problem. Take some time and look down
into the inspection cover on the bell housing, and make sure you haven't
lost a bolt off the pressure plate. There are a lot of bolts and hardware on
there, that can come loose and fall off, causing an imbalance.
If the engine has been rebuilt over the years by a backyard mechanic, then
chances are it was never properly balanced. Of course the flywheel is over
60 lbs, so if the crankshaft was ever ground then the centerline can be off
by a few thousandths. It doesn't take much for a 60 lb weight to vibrate if
its not centered properly. This can only be repaired by taking everything
apart and sending it out for balancing.
If the flywheel has ever run loose on the crankshaft, it will wear out the
mating surface and will always vibrate. No matter how tight you tighten the
4 screws, they are no match for the heavy flywheel. We have learned to test
this surface for a tight fit before assembling the engines.
Next most complicated problem: if the engine has been balanced, but you are
using a lightened flywheel, or a crankshaft with the "Add-On"
counterweights, then the vibration could be a harmonic vibration, which
can't really be balanced out. You may just have to live with it.
The Float-a-motors, will take out a lot of the vibration, especially the
vibration that you feel when decelerating. We use them on almost every car
we build, and I highly recommend them.
Hope this helps
Bentley C. Bohanan
Bentley's Antique Auto Service, Inc
95 W Ridgeway Rd
Maysville, GA 30558
phone 678-407-1947
website www.mymodela.com
email benn...@windstream.net
--------------------------------------------------
From: "Del Alspaw" <dela...@gmail.com>
Sent: Saturday, January 07, 2012 1:01 AM
To: "Model A Ford Forum" <modelaf...@googlegroups.com>
Subject: [ModelAFordForum:443] High speed vibration
> Hello,
Lockwood, Fred C
Del
Bentley's reponse is much fuller and much more interesting than mine. he has worked on a multitude of model A's. Although an engineer by training, I have only ever owned two. Some of his suggestions imply a lot work, I would therefore want to be certain that it is engine related in the means he suggests. The coasting test could mask a problem under load. At least model A mechanics are simple and frugally resolvable given a measure of common sense and reflection.
He mentions harmonics and has tempted me to add an aside. Four cylinder engines suffer from inherent imbalance because, in simple terms, the pistons are not halfway down the bore when the crankshaft webs are horizontal. Vibration can be noticeable, even disagreeable, at critical rpm, the extent being dependent on design features. Modern engines have short strokes, the principal feature which minimises the problem. My model A's exhibited harmonic vibration, but not to a disagreeable level. Bentley mentions design features I am unaware of. Over such a long production run there must have been subtle changes and after all these years after sales add-ons. If it were me I would telephone Bentley for further comment.
I would happy to know how you get on but at an alternative and leisure address: maisonb...@yahoo.fr. As it implies I am these days rater too far from model A's.
Fred
________________________________________
From: modelaf...@googlegroups.com [modelaf...@googlegroups.com] on behalf of Del Alspaw [dela...@gmail.com]
Sent: 07 January 2012 06:01
To: Model A Ford Forum
Subject: [ModelAFordForum:443] High speed vibration
Hello,
--
Bentley Bohanan
time.
Thanks
Bentley
--------------------------------------------------
From: "Lockwood, Fred C" <f.loc...@imperial.ac.uk>
Sent: Monday, January 09, 2012 7:56 AM
To: <modelaf...@googlegroups.com>
Subject: RE: [ModelAFordForum:447] High speed vibration
John Miller
On Monday, January 9, 2012 10:09:04 AM UTC-5, Bentley Bohanan wrote:
Email works better for me, then I can return the comments in my "Spare"
time.
Thanks
Bentley
--------------------------------------------------
From: "Lockwood, Fred C" <f.loc...@imperial.ac.uk>
Sent: Monday, January 09, 2012 7:56 AM
> From: modelafordforum@googlegroups.com [modelafordforum@googlegroups.com]
> on behalf of Del Alspaw [dela...@gmail.com]
> Sent: 07 January 2012 06:01
> To: Model A Ford Forum
> Subject: [ModelAFordForum:443] High speed vibration
>
> Hello,
> I need some suggestions for what and where to look. My 29 tudor has a
> vibration when it hits about 50 mph or when you reach top end rpm
> between shifting. It seems to be in the drive train. She does not
> knock or smoke or use oil (except for the rear seal). I have replaced
> the fan and water pump. I went down a grade and popped her out of gear
> and she coasted past 50 and was smooth as silk. She is all stock and I
> never had the drivetrain apart since I have owned it. I was told the
> tranny was fairly new when I bought her. Any ideas? Flywheel? Rods?
> Crank? Some folks have told me its due to the solid rear engine
> mounts. Does not seem to worse with time or anything just keeps me
> from going over 50 and I suppose thats not all bad ... hahaha...
>
> Thank you or time - Del
>
> --
> You received this message because you are subscribed to the Google Groups
> "Model A Ford Forum" group sponsored by The Shade Tree A's Model A Ford
> Club of Augusta, Georgia: http://shadetreeas.org/
> To post to this group, send email to ModelAFordForum@googlegroups.com
> To unsubscribe from this group, send email to
> For more options, visit this group at
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>
> --
> You received this message because you are subscribed to the Google Groups
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