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1971 CDV - Vibration at HWY speed under load

Started by impalamansgarage, February 09, 2016, 03:21:23 PM

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impalamansgarage

Hello all. When driving my 71 CDV above about 60 mph I hear a vibration coming from the front of the vehicle. Under load going up a hill is much more
prevalent. Letting off the gas makes the sound go away. It is a slowly oscillating vibration. Waw...... waw.......waw.......

I have a car lift and I put the car in the air and ran it up to 70 mpg briefly and could not hear the noise.  The front wheels spin freely and I cannot hear a bearing noise when I spin them by hand. The rear diff gears look good as I check in the diff last night.

I am thinking that this is a vibration coming from the engine. Maybe a bracket is hitting something under load when the engine is providing torque.

Both motor mounts and the transmission mount are new. The AC compressor is also new and works well.

Any thoughts or guidance would be greatly appreciated. The driving experience is ruined by this sound.
impalamansgarage
https://www.youtube.com/c/impalamansgarage
1971 CDV (http://bit.ly/1QylevA)
1981 CDV (Sold)
1992 SDV (Sold)
1963 Fleetwood (Teenage Junker Project - Sold)

bill06447

Axle bearing or U-joint come to mind (pull the RH drum and check for oil a worn bearing will manifest itself as an oil leak first)

Bill

Scot Minesinger

A great place to start is the shop manual at the beginning of the book, it has a thorough chapter on vibration and how to isolate it.  I think you are most of the way there with the only under load at high speed.  There will be suggestions on how to cure this type of problem. 

One of my friends suffered a vibration problem and via the shop manual it was diagnosed as a bad fan clutch, no wonder the water pump prematurely failed before.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

TJ Hopland

I presume a 71 uses the 'CV' type of U joints?   When those wear they can change behavior depending on load.   

I never tangled with them on the Cads but on the trucks if you pulled the shaft assembly and the joint end just flopped loose it was shot.   After you got it rebuilt it would just about hold its own weight and stay straight.   
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

impalamansgarage

bill06447
I've yet to pull off a rear wheel as I have not had this car very long but I will try that.

Scot Minesinger
I just got a shop manual. Good tip. Thanks!

TJ
This is a Deville so it is rear wheel drive. Not sure where you are going with this one.
impalamansgarage
https://www.youtube.com/c/impalamansgarage
1971 CDV (http://bit.ly/1QylevA)
1981 CDV (Sold)
1992 SDV (Sold)
1963 Fleetwood (Teenage Junker Project - Sold)

impalamansgarage

On my 78 vette the AC compressor belt is notorious for vibrating at certain engine RPMs. This is a common problem for vettes of that time period. The AC belt is pretty long.

As you know there are two belts driving the compressor and the PW pump. I will try to tighten them and see if there is a difference. They seem OK but could be tighter to suite me.

One other thing to note is that this car does not have a clutched fan. I guess what you call it is a flex fan.
It appears to be stock. I don't think the sound is coming from there.
impalamansgarage
https://www.youtube.com/c/impalamansgarage
1971 CDV (http://bit.ly/1QylevA)
1981 CDV (Sold)
1992 SDV (Sold)
1963 Fleetwood (Teenage Junker Project - Sold)

"Cadillac Kid" Greg Surfas 15364

Don't forget to check and tighten all the front end sheet metal, bumpers, bumper mounts and grill.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

Scot Minesinger

TJ is right.  If you remove RWD drive shaft and the "universal joint" end that slips into trans tail with drive shaft on your work bench does not stay in the position you move it to, but flops around always going to where gravity pulls it, then it is shot.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

TJ Hopland

Possibly called a 'double cardan joint'?   


Thanks to 4x4shaft.com for the photo.   The ones Cadillac often used were not identical to this one but similar.

They are/were commonly used on trucks apparently due to the more extreme drive shaft angles.   Cadillac apparently used them due to lack of angle and to make sure things stayed extra smooth.   There was a discussion about them a while back and the thought was that rather than place the rear end and engine/trans in the ideal location for the drive shaft to work like most manufactures did Cadillac put them where they needed to be for the rest of the body and styling to work so they gained the look they wanted and 2 more inches of legroom or something like that. 

I'm thinking a 71 had them and my point is that they can act a lot different than the regular single joints when they wear. 
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

cadman56

If the vibration were coming from the driveshaft wouldn't the vibration be much faster than described, like a difference in harmonics?  Seems like to me it might be belt or possibly an unevenly running engine or exhaust resonance?  Just some thoughts.  Larry
1956 Cadillac Coupe deVille (sold)
1956 Cadillac Convertible (sold)
1956 Cadillac Eldorado Seville (sold)
1967 Cadillac Eldorado (sold)
1968 Cadillac Convertible (Sold)
1991 Cadillac Fleetwood Brougham dElegance
Larry Blanchard CLC #5820

impalamansgarage

I have had the drive shaft out recently because the transmission
tailshaft seal was leaking. I replaced the seal.

TJ
The drive "slip yoke" (which inserts into the transmission)
does move freely about but it does not flop around. It seems
tight enough however.

The double cardan joint as you call it does not flop down. It stays in place
when the drive shaft is lying on my roll-around table. I do not think
there is an issue with the drive shaft.
impalamansgarage
https://www.youtube.com/c/impalamansgarage
1971 CDV (http://bit.ly/1QylevA)
1981 CDV (Sold)
1992 SDV (Sold)
1963 Fleetwood (Teenage Junker Project - Sold)

impalamansgarage

#11
cadman56

These were my thoughts as well. I am going to make a PS pump tensioning tool, as outlined in the shop manual, and tighten
the PS/Compressor belts to see what the effect is.

This sound is barely audible between 30 and 55 mph......and I mean JUST barely. Then when you get to hwy speeds it begins
a slow oscillation........ waw..........waw...........waw............. were each "waw" is probably one second apart.

I'm on the verge of buying one of those Steelman Chassis Ears.



impalamansgarage
https://www.youtube.com/c/impalamansgarage
1971 CDV (http://bit.ly/1QylevA)
1981 CDV (Sold)
1992 SDV (Sold)
1963 Fleetwood (Teenage Junker Project - Sold)

dplotkin

Quote from: impalaman on February 10, 2016, 10:51:23 AM
This sound is barely audible between 30 and 55 mph......and I mean JUST barely. Then when you get to hwy speeds it begins
a slow oscillation........ waw..........waw...........waw............. were each "waw" is probably one second apart.
I'm on the verge of buying one of those Steelman Chassis Ears.

Is this just sound, or sound and vibration? Sounds to me like exhaust resonance. Is it a stock single exhaust? have you changed anything?

Dan
56 Fleetwood Sixty Special (Starlight silver over Dawn Grey)
60 Buick Electra six window
60 Chrysler 300 F Coupe
61 Plymouth Savoy Ram Inducted 413 Superstock
62 Pontiac Bonneville Vista
63 Chevy Impala convertable
63 Ford Galaxie XL fastback
65 Corvette convertable 396
68 Chrysler New Yorker

Scot Minesinger

These are very difficult to solve over the internet.  I hope we helped.

Feel very confident you will figure it out.  I just use a pry bar to tension power steering belt - you are making a tool-wow!  That is a testament to your thoroughness, that is what makes me think you will get the vibration resolved. 

Unless a power steering pump pulley is bent or power steering pump is messed this is an unlikely source of the trouble.  Have seen very loose and too tight PS belts and it had no impact on vibration.

My father in law always said "it is something simple", and he was right most of the time.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

impalamansgarage

dplotkin
There is a vibration as well but it is not bad. You can feel it a little throught the gas pedal.

Scot
I usually use a pry bar as well but there is nothing I can see to pry on. When I saw
the tool design outlined in the manual I had to have it! I have two other cars with
this type of pump so I should come in handy.

I'm hoping it's not the transmission..... althoughI've never heard a trans make
a noise like this.... but still.

I tightened the belts tonight with the tool. I'll give it a test drive tomorrow.
I'm not hopeful. We'll see.
impalamansgarage
https://www.youtube.com/c/impalamansgarage
1971 CDV (http://bit.ly/1QylevA)
1981 CDV (Sold)
1992 SDV (Sold)
1963 Fleetwood (Teenage Junker Project - Sold)

impalamansgarage

dplotkin
This car is bone stock except for an after market aluminum radiator that the previous owner installed.
I supposed it might be vibrating against the frame. I can check that.

The exhaust is all stock as well except for a new muffle. It seems to be solid although I've not yanked
on it extensively. LOL.... I will check.

This car was owned by a very long lived fellow and apparently spent some time in storage.
The story from the previous owner was that he old man worked for a Caddy dealer, thus the good
condition of the car. The interior is absolutely original and in fantastic shape. The paint and vinyl top are original as well.
impalamansgarage
https://www.youtube.com/c/impalamansgarage
1971 CDV (http://bit.ly/1QylevA)
1981 CDV (Sold)
1992 SDV (Sold)
1963 Fleetwood (Teenage Junker Project - Sold)

cadman56

One other question - did you purchase both PS/AC belts at the same time?  It used to be you had to purchase a 'matched set' of belts when running multiples on a device.  That meant the belts came from the same manufacturing drum.  They stopped selling matched sets about mid-way through my tenure of owning a NAPA parts store.  Your belts may be the problem.  Also make sure the PS pulley is completely at a 90 deg. to both belts.  If not, one belt will always have a different tension from the other.  Good luck.  Larry
1956 Cadillac Coupe deVille (sold)
1956 Cadillac Convertible (sold)
1956 Cadillac Eldorado Seville (sold)
1967 Cadillac Eldorado (sold)
1968 Cadillac Convertible (Sold)
1991 Cadillac Fleetwood Brougham dElegance
Larry Blanchard CLC #5820

Jon S

Quote from: Scot Minesinger on February 10, 2016, 09:35:32 PM
I just use a pry bar to tension power steering belt - you are making a tool-wow!  That is a testament to your thoroughness, that is what makes me think you will get the vibration resolved. 

I could never figure out why Lincoln (Ford) added a 1/2" drive cutout to their brackets to make belt adjustment a simple task with a 1/2" drive ratchet and Cadillac (GM) made one use a pry bar. 
Jon

1958 Cadillac Sedan De Ville
1973 Lincoln Continental Coupe
1981 Corvette
2004 Mustang GT

Coupe Deville

Quote from: TJ Hopland on February 10, 2016, 09:29:57 AM
Possibly called a 'double cardan joint'?   


Thanks to 4x4shaft.com for the photo.   The ones Cadillac often used were not identical to this one but similar.

They are/were commonly used on trucks apparently due to the more extreme drive shaft angles.   Cadillac apparently used them due to lack of angle and to make sure things stayed extra smooth.   There was a discussion about them a while back and the thought was that rather than place the rear end and engine/trans in the ideal location for the drive shaft to work like most manufactures did Cadillac put them where they needed to be for the rest of the body and styling to work so they gained the look they wanted and 2 more inches of legroom or something like that. 

I'm thinking a 71 had them and my point is that they can act a lot different than the regular single joints when they wear.

For what its worth, my 72' has that same set up in the picture above. I would think 1971 is the same. Like double ujoints in a special carrier.
Also, impalaman start a new thread and introduce yourself. Your 71' looks beautiful. I would love to see it. Post some pictures of your car. Ive got a 1972 CDV with 28,000 original miles.

-Gavin
-Gavin Myers CLC Member #27431
"The 59' Cadillac says more about America than a whole trunk full of history books, It was the American Dream"

impalamansgarage

Quote from: Jon S on February 11, 2016, 10:54:08 AM
I could never figure out why Lincoln (Ford) added a 1/2" drive cutout to their brackets to make belt adjustment a simple task with a 1/2" drive ratchet and Cadillac (GM) made one use a pry bar.

Amen to that.
impalamansgarage
https://www.youtube.com/c/impalamansgarage
1971 CDV (http://bit.ly/1QylevA)
1981 CDV (Sold)
1992 SDV (Sold)
1963 Fleetwood (Teenage Junker Project - Sold)