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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

NO CHANGE!

New rear axle bearings did nothing. Sound is still there. Accompanies a vibration once the car gets around 55 mph. If you go up a hill, at around 65 mph for example, and accelerate the noise and vibration get worse. The vibration will rattle the little metal door on the passenger's cigar lighter.

I started looking that the section of vibration diagnosis in the front of the shop manual. Will start going through those steps tomorrow. From indications it sounds as though it may be a torque sensitive issue.
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

Mr Chevrolet,
From what you have said in previous posts I would be looking at the driveshaft's constant velocity joint.  If worn or if incorrectly installed it will product the symptoms you describe.
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

Agree with Greg. 

Also, you may want to check the rear trans mount as sometimes those go causing a vibration.  If that is questionable, the engine mounts in front should be inspected too.  One of my friends has this problem on his 1975 Cadillac Fleetwood and it has been diagnosed as drive shaft, he is looking for one (the Fleetwood is a little longer than DeVille).  The trans/driveshaft/diff are all similar from 1970 thru 76 (2.93, 3.15 (1970-74), and 2.76 (1975 & 76)).

I think looking at the shop manual under vibration section is a good place to continue the process. 

I have had to replace the rear axel bearings in my two 1970 Cadillacs once they reach about 100k miles.  The noise was just ever so slightly noticeable at the time of rebuild.  Now you are probably set for life on rear axel bearings for this car, one less thing to worry about.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

impalamansgarage

Quote from: Scot Minesinger on February 20, 2016, 08:30:04 AM
Agree with Greg. 

Also, you may want to check the rear trans mount as sometimes those go causing a vibration.  If that is questionable, the engine mounts in front should be inspected too.  One of my friends has this problem on his 1975 Cadillac Fleetwood and it has been diagnosed as drive shaft, he is looking for one (the Fleetwood is a little longer than DeVille).  The trans/driveshaft/diff are all similar from 1970 thru 76 (2.93, 3.15 (1970-74), and 2.76 (1975 & 76)).


I replaced the trans mount recently. Also the engine mounts were replaced by the previous owner and appear new. I checked the bolts on them and they are tight.

One thing I did not mention was that two of the bolts on the drive shaft flange which connects to the diff are replacements. Apparently two of the bolts were stripped out at one point. Some one bored out the holes a little and used slightly larger bolts with lock washers and nuts. It appears to be grade 8 stuff and both bolts appear to be the same length. I have no idea whether or not it is balanced.

I will post some pics of 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

#64
Drive Shaft - All the wet oil is from me using WD40. Not car leaks.
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

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

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

Took another test drive this morning. Varied the throttle in both 2nd and 3rd gear.

In 3rd gear above 50, if you accelerate (without down shifting.... lugging the motor a bit) the problem is very pronounced. Noise and vibration.

If you leave the car in 2nd gear and speed up past 50, the problem is hardly noticeable if at all.

It rears its head when you lug the engine.
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)

Scot Minesinger

I would think that the two good original bolts would align shaft so it is centered.  Plus if it was out of center the faster spinning (non-engine lug) would show itself in vibration fairly independent of anything except drive shaft rotation speed.  This happened to me once on a truck where engine lugging produced vibration, and it turned out to be the automatic transmission (2007 GM full size truck w/V-8).
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

Jeff Rosansky CLC #28373

I am still going to suggest you stick a camera undwr there to see what is actually moving.
Can't hurt.
Jeff
Jeff Rosansky
CLC #28373
1970 Coupe DeVille (Big Red)
1955 Series 62 (Baby Blue)
Dad's new 1979 Coupe DeVille

Roger Zimmermann

#70
Quote from: impalaman on February 20, 2016, 01:10:31 PM
Drive Shaft - All the wet oil is from me using WD40. Not car leaks.
Is that casting part at the differential cracked or is that an optical illusion? (the second picture from the drive shaft)
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101

The Tassie Devil(le)

Quote from: Roger Zimmermann on February 21, 2016, 05:04:26 AM
Is that casting part at the differential cracked or is that an optical illusion? (the second picture from the drive shaft)
A shadow caused by the flash being slightly off centre to the camera lens/CCD.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

Roger Zimmermann

Bruce, I'm not sure that we are "speaking" about the same thing. Have a look at the red arrow in the picture...
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101

TJ Hopland

That looks like a shadow from the rib in the casting. 
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

Roger Zimmermann

1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101

Jon S

#75
Never experienced a problem like this (fortunately), but wouldn't any looseness be more prevalent  when the throttle is released?  I would think under load any looseness/slack would be taken up by the load.  In other words, I would have expected the noise/vibration to appear releasing the accelerator; not under load.   Just my thoughts.

Impalaman - is there a clunking when you release the accelerator and then give it gas lightly in high gear?
Jon

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

impalamansgarage

Quote from: Jon S on February 21, 2016, 10:22:53 AM
Never experienced a problem like this (fortunately), but wouldn't any looseness be more prevalent  when the throttle is released?  I would think under load any looseness/slack would be taken up by the load.  In other words, I would have expected the noise/vibration to appear releasing the accelerator; not under load.   Just my thoughts.

Impalaman - is there a clunking when you release the accelerator and then give it gas lightly in high gear?

No. The drive train is tight.

That is a shadow in that photo but it startled me upon first examination.  :)

The only auto transmission problems I've ever experienced in any car came in the form of slippage. I've never heard an auto trans make a noise like this but I'm started to suspect. Saw this post over
on another forum:

"Took my tranny to get rebuilt. It was planetary gears. They looked all chewed up. Turns out that is the reason I had a very slight vibration in 3rd gear under very hard acceleration for many years. Thanks for the help guys."

http://www.thirdgen.org/forums/transmissions-drivetrain/191228-grinding-noise-torque-converter.html
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)

savemy67

Hello Impalaman,

There are two clues/symptoms mentioned in your prevoious posts that you may want to investigate more closely.  Based on no change subsequent to replacement of the rear wheel bearings, the first clue is the replacement bolts in the differential pinion flange.  Speculating on why the bolts were replaced leads one to think that there was a problem with the differential, the driveshaft and double Cardan joints, or the transmission.  If the car was maintained by a Cadillac dealership, what circumstance would cause a dealership to replace two of the four bolts?  You may need to consider the possibility that at some point there was a significant problem with one of the driveline components.  Since the driveshaft is relatively easy to get to, check it first.  From under the car, give the driveshaft a good back and forth yank near each end of the driveshaft - radially (side to side), not axially (front to back).  Rotate the driveshaft 90 degrees and repeat.  Do this two more times to check for any looseness in the double Cardan joints.  This may expose looseness in the differential and or transmission as well.  To be absolutely sure the driveshaft is perfect, you could take it to a shop that could check it for balance (include the four pinion flange bolts).

The second clue is that the problem rears its head when the engine lugs.  When the speed of the transmission output shaft multiplied through the differential fails to provide enough twisting leverage (torque) required to move the car at that moment, the engine will lug.  One of your posts mentioned lugging in third gear.  At a lower road speed, can you get the engine to lug in second?  If not, that would lead me to consider the transmission may have a problem.  You could do a pressure check on the transmission before pulling it out of the car.  The shop manual should have the specs for pressure testing the transmission.

Diagnosing problems like this can be time consuming.  Using the shop manual vibration diagnosis checklist should help.  By no means am I an expert at these things, but using a methodical approach will minimize the money spent to resolve the problem.  If the worst case scenario is having to rebuild the transmission, would that be a bad thing for a 45 year old car that has sat for a while?  It could put a dent in your wallet, but that pain will subside the more you drive your '71.

Respectfully submitted,
Christopher Winter
Christopher Winter
1967 Sedan DeVille hardtop

dadscad

A damaged flex plate may cause similar symptoms. It could be warped, or cracked, wouldn't hurt to pull the inspection cover and give it a good look with a bright light.
Enjoy The Ride,
David Thomas CLC #14765
1963 Coupe deVille

impalamansgarage

Thanks for the tips guys. I will check those items out as soon as I can. I also plan to go to the transmission shop and have a pro ride along with me and listen to this thing.
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)