VCCA Home Forums TECHNICAL - 1945 AND NEWER 1949-1954 Vibration

1951 Chevrolet Deluxe 4 dr powerglide Original **.
I would own a perfect driving car if I could cure this annoying vibration I have worked on for nearly a year.
Here as best I can describe it is what it does. Up to about 35 MPH it is tolerable after that it is progressively worse. It sounds/feels similar to a bad "U" joint but it isn't that. It is a harmonic type of vibration like a twin engine boat or aircraft "out of sync".
I have replaced to "U" joint and the front D/Shaft bushing and all related parts in the "bell". ( was okay but changed it anyway)
New transmission mount and front motor mounts because it sounds like the engine was sitting on the frame. (no change)
If I am driving 50 MPH and shift into Neutral the vibs stop! (so not the driveline??)
If I rev up the engine and the car is not moving I can feel some vibration at higher RPM but only the vib, not that disturbing harmonic situation.
my car has a 53/54 PG ** because it starts in low and shifts to drive and has a "kickdown" lever on side on tranny but no linkage. I don't think this could have any effect on my vibration problem although it could have been installed wrong??? balance marks not aligned ??
I think the problem could be the torque converter or a bearing/bushing in that area?
If I only drove 30 MPH the car is fine, but I like 50-60 and it is horrible. I am lost for what to do? Any advice???? I have had great help in the past.
You can feel the vibration in the front seat and steering wheel.
Thx
Mike

know we have discussed this before and often wondered if you solved the problem.
Here are some things I would do or suspect.
Loosen all the converter to flex plat bolts. see if you can rotate one or the other and re-bolt .
(there was no index marks)
Remove bolts and I think the converter will move back enough so you can run the engine without turning the converter.
The nose of the converter SHOULD center OK in the crankshaft - I hope.
Converter bushing worn or converter loose on the front pump.
Hard to tell was was screwed up in the conversion and what converter was used.

Mike,

I had a similar vibration with my '49 Fleetline, and it was caused by the exhaust pipe being bolted directly to the support that extends from the frame, with no rubber isolation between the exhaust and the frame. Made a world of difference when I found and installed the correct hanger parts. Like you, I could feel vibration in the steering wheel and in the driver seat--and also about 50 mph.

A quick look under your car can verify this, before you proceed to Gene's excellent (as always) advice.

The proper way to attach the exhaust is described in the shop manual.

-Mark

Been battling the exact same problem, with the exact same car, with the exception of my powerglide being original to the car. My vibration STARTED when I replaced the transmission mount. 35 mph or below, car is fine. Most times I can drive the car at 30 to 35 mph for 25 or 30 miles, and then sneak up to 45 or 50 and it is tolerable. Jump in it and try to drive it 50 mph right off the bat, and it is nasty. I've replaced torque tube bushings, u joints, differential carrier bearings, engine mounts, yoke, re-shimmed the ball twice, tried a different trans mount etc,etc,etc,...... This problem is so frustrating, i would just as soon get rid of the car, except you can't sell it vibrating like it is. I've been working on this problem for two years now, had many suggestions from this forum, have yet to solve the problem. It is going into storage tomorrow, so I guess I'll spend all of my spare time next year working on it. If I solve it next year I will be sure to let y'all know what I find, but right now I don't want to even look at the dang thing! Obviously some of these Chevies are extremely susceptible to this problem, and it is probably one of the reasons they went to an open drive line. Maybe I will get lucky and cream a deer on the way to the storage facility, and just call it good. Take the money and go buy a F**d

Gene, Mark and possible new future Ford owner thank you for the reply!
Gene I found no logical solution so I have been working thru other smaller and fixable problems. I do not have a lift so unbolting the rear mount and unbolting the torque converter and moving it back to rotate the clocking of the engine to T/converter has prevented me from doing so up to this point but I'm am so sick of the annoying sound and vibration I am ready to go to the next step. I even shopped for a lift but at 71 years old I keep thinking I am close to stopping this wrenching and just buy "perfect" cars that need nothing. However I do know that is impossible.
Why if is an out of balance situation or lose bolts is it so smooth at 30 mph and will run you out of your mind at 60?
I wish there was an expert old car shop here or even near Branson, MO.
Bad thing is this Chevy "drives" so well and does most of the other things right, I hate giving up or letting a '51 Chevy whip me. I grew up working on these cars and in fact my parents bought a sweet low mileage '51 PG like this one in 1952 and was the car I started to drive in '53, the very reason I bought it was the nostalgia and the familiarity of it.
Still stumped but not quitting yet,
Mike

You said the vibation quits when you put the car in neutral. Sounds like the vibration occurs when the driveline has a pull on it.

To make sure. with the transmission in neutral, does the engine vibrate when raced at high RPM?
I have had some weird vibrations caused by rear end and or axle bearings.

If it is in the driveline, you can do further troubleshooting by jacking up one rear wheel and then the other and run it at 50 MPH. If you get the vibration on one side only then it is bearings related to that side. If it vibrates on both sides then it is probably bearings that are related to both sides. Be sure to use jackstands and chock the other wheels.

"Why if is an out of balance situation or lose bolts is it so smooth at 30 mph and will run you out of your mind at 60?"

Your vibration concern is a harmonic issue, as you stated.

Compare this vibration which you are experiencing to a wheel that has been mis-balanced or has lost one of its wheel weights.

That tire does not vibrate from zero MPH to whatever MPH. Instead it finds a " specific spot" where the steering wheel could shake out of your hand. Going above or below that certain "spot" or MPH, and the vibration is lessened, if not totally gone.

Although rotating the torque converter to flexplate bolt up positioning may take time, moving one position, then road testing .... I would think this would be a good place to begin, as suggested by Gene.

Another good thought, as stated, is to inspect the exhaust system mounting AND clearances, from the exhaust manifold back.

When accelerating or attempting to maintain a higher speed, the engine assembly is attempting to rotate to the passenger side. When put into neutral, the engine assembly "relaxes", eliminating the torque/rotation.

If exhaust clearances are too close, with engine in off position, exhaust may be "grounding" against frame or body parts, when engine is torqueing to the right.

This might be an "end run" solution for you, but since it sounds like you have a drive line related issue, have you considered changing your ring and pinion differential gears to the 3:55:1?? Your engine will turn slower rpms at 50 and might cure the issue.

On another note, it sounds like an internal engine issue if you've eliminated the drive shaft,clutch, trans, rear components. Possibly main bearings or oil pressure at high speeds. Hook up an oil pressure gage so you can see exactly how much you've got at high speeds. I would also do a compression check to check your cylinder pistons/rings, valves.

Good luck.

Powerglide cars already have the 3:55 ratio in the rear axle. I don't think the vibration lies anywhere in the engine itself. I'm dealing with the same issue, and if you had main bearing problems, the engine would have low oil pressure, and more than likely the rod bearings would be shot too, making a rattling noise. This vibration can be felt through floor pans and steering wheel. With the steering wheel being so big on these cars, it acts just like a big bell

I would go back to the origianl thing where the vibration began.....changing the transmount.
In case #2 he has a 1953 PG in a 1951. The trans. mount is in a different location and of a different type in 1953 compared to the 1951.

Okay here is what I've done and what changed.
First I thought it was the U-Joint because it felt like a U-Joint. While I was there I replaced the torque tube bushing with a "Oakie" bushing which fit so tight the yoke would not turn so I machined off a couple thousands because I could NOT get the bushing out once installed. Final fit was good, but so was the original one. After I replaced the "bell" seals and spacers, installed 1/2 pint ATF in the bell, I test drove it and NO DIFFERENCE!
The feel and sound also felt like a couple of you said when the exhaust pipe is touching the body/frame. I replaced the entire exhaust front to rear including hangers .....NO Difference.
Then I thought well maybe the engine is setting on the frame? When I examined the rear transmission mount and saw how deteriorated it was and soaked with the leaking for 64 yrs PG transmission fluid, I thought I'd found it! I researched the mount thoroughly and bought the mount for a 1951 passenger car and it was identical to the one that came off and bolted right up to the '53 PG because while the cars are different the transmission casting for the mount is the same. Fit was perfect and required no forcing to install. Guess what, NO CHANGE at all!
So I go to the front engine mounts and replace both LH & RH frt mounts.NO DIFFERENCE.
Only difference I see in the 1950-1954 PG's is that an addition of a valve body to cause the transmission to start in low and shift to drive automatically, but the mounts are the same, I think.
Again, it ain't the U-Joint, transmission/engine mounts or the exhaust touching anything.
If setting parked, I rev up the engine I can feel the vibration ...a little but not horrible. If I take the car to 50-60 MPH I want to yell it is soo bad! If I simply let off the throttle and coast down it vib. even down to about 20 MPH. But not too bad.
If at 60 MPH I put the car in neutral and coast it is so smooth and quiet it seems....well normal.
So what is left but transmission front bushing or flywheel coupling? Seems like if trouble was in transmission it would do it while coasting, but I am still stumped. I don't think I can with only a floor jack, unbolt enough to separate the trans from the engine enough to rotate the bolted up coupling of the engine and transmission and re-clock the bolted two together??? I don't know?? And how far apart to they need to be to accomplish this? My shop manual says there are "X" marks that need to be aligned on the flywheel and converter??
It says that once they are together you cannot see the "X"'s???
Moving the shift lever from forward to reverse there is no slack, it is very tight (Drive line).
It is not oil pressure or rod bearing.
If I try to match the engine rpm to approx transmission speed in neutral I cannot duplicate the vibration.
This is frustrating to an old car guy that usually finds the problem but no so thus far!
Mike

You are not being asked to separate the transmission from the engine.

Instead, the plan is to "reclock" the converter to the flexplate ....... one bolt hole position at a time.

One thing I thought of. The trans mount will bolt on to the plate either way, however there is a notch on one side of the mount for clearing a part of the transmission housing. Make sure that the notch is on the correct side.

First I want to thank all of the nice folks for advice so far and I am going to ask for one more thing. BTW I had not discovered the rear (side) engine mounts were bad and because I had already replaced all the other mounts I ordered and just replaced both sides. The left one was broken so bad that it came off as two separate pieces, the rt side was fine but I replaced both. I was hoping that might had been the hidden culprit but not a chance. I wanted to do that before re-clocking the engine/torque converter.
So, here is my question as I am ready to tackle that job. I have shop manual and it does NOT cover that job. Sounds like some of you have, please tell me the sequence and basically how I do this? Is there a cover under the converter that I get to the bolts or where do I go for them and since I don't remember buying that special tool to turn the engine, can I rotate either the torque conv. or the engine with a large screw driver or pry bar? I am hoping all those parts will align after I pull out the last bolt so it will go back together. I need a tiny bit of encouragement before I start.
Also, I know Chevrolet built about a million of these and they didn't vibrate so I know something in my car is just broken, worn out or way out of balance.
Help
Mike

I doubt very much as it would be the side mounts. They carry no weight but just prevent the engine from "twitsing" under power.
Yes, to turn over the engine use a long screw driver
You can access the converter bolts through the opening right behind the side block drain cock.
The offical way to turn over the engine was by removing the tin plate at the lower front of the P.G. unit. A special tool was used to reach up in there to turn over the engine. May be easier to remove the spark plugs and turn over the engine by the fan blade pulling on the fan belt (or making it very tight) so it dosen't slip.
After the converter is unbolted it should push away fron the flex plate slightly alowing it to turn freer.Mark with a yellow tire crayon so you can tell how much the converter or fly wheel has moved and so you can get it back to the origianal psition if necessary.
See shop manual under P.G removal. May help a little.
Good Luck

Knowing how these old fan blades fracture, then fly off like a missile, I would not touch the fan blades, in an effort to reposition flywheel position, etc.

I knew an individual, who lost his life, while under the hood of his 235" Chevy.

He was timing the engine, revving the motor. Fan blade came off, then lodged into his skull, ending his life..

A new fan blade should be on the "to do" list for all of us, with our old Chevys.

Correct. I replaced the fan blade on my cars at the beginning.

page 7-44 shows where you will access the flywheel to converter bolts. Paragraph 19 states that there are 6 of them. After those are out they are saying you can slide the converter towards the transmission. Then you have to rotate either the engine or the converter to line up with next hole, the hole 180 degrees out, whatever you want to do. You will probably have to use a longer bolt to thread into one of the converter mounting hole to pull the converter back towards the flywheel when you get to your new position. Definitely mark the original location, as the factory marks can only be seen with the transmission removed. This is all provided that the converter will slide back far enough to clear the flywheel, and then rotate to the new position without catching on the flywheel

It would also be a good time to see if the converter "rocks" on the front of the transmission.
Also if you can determine what flywheel and converter was used on the later 1953-54 transmission.

Has any new conclusion been reached with the vibration problem?

I had the same exact issue with a 50 PowerGlide. Just like the original poster of this thread. Mine did not vibrate under 40 mph. Between 40 and 55 it vibrated through the floor very noticeably. I replaced u joint, checked exhaust, etc. My car had weak rear leaf springs. Believe it or not, the noise and vibration totally disappeared at all speeds the moment I installed a helper leaf spring kit. The helper springs raised the rear about 1 to 2 inches. The vibration never returned. Perhaps, the driveline angle changing ever so slightly when the springs become week caused the vibration. Returning it to a proper height caused the feel and sound to never return. Something worth trying or taking a look at.

When I have a heavy load in the back of my 1950 a vibration, though not real bad, comes on over 60 MPH.

When "pinion angles" are affected, the vibration goblins can make their appearance.

Is there somewhere to find specs for the pinion (torque tube) angle. I am familiar with the problems of improper drive line angles from my heavy truck experience where it was one of the most common causes of vibration.

I am guessing the driveline angle actually decreases as the rear end is lowered. Is it possible that the vibraton is caused by the U joint splines are in a different position placing a load on the U joint or?