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

A good friend of mine has a '50 Chevy coupe which has a vibration problem starting around 45 mph. If he shifts into neutral, the vibration goes away. If he depresses the clutch pedal, the vibration remains. I was thinking the pilot bushing for the tranny input shaft, but ?????
Any other ideas before we tear into it?
Thanks,

-Bob

I have the same problem with my 1950 Chevy. I have replaced all the gears & bushings in the tranny, the output bushing and replaced the bushing in the torque with an Okie bushing. Nothing seems to help.

I had the same problem 50 years ago with my 49 Chevy. I took it to a local mechanic and he put some kind of clamp on the torque tube. Didn't help a bit. I'm convinced that it is a problem with these years.

I had a vibration in the 52 which at times would also kick out of 3rd aaround 55 mph. The manual addresses this very problem. I tore mine down, replaced the needle bearings,new front input shaft bearing, 2nd gear thrust washer, new bushing at the back of the transmission, and a bearing seal kit from the "Filling station" for the drive shaft. fixed the problem nicely.

I did all that on my 50. Didn't change a thing.

Many years back a friend with a 1949 had this problem AFTER he had the flywheel lightened. (don't remember just what we called it back then).We always blamed it on the flywheel being out of balance.After much hard driving the main bearings pounded out due to the vibration.If I remember correctly - reving the engine up to about 2000 + RPM in neutral would also bring on the vibration.

If your vibration comes only when the drive shaft is turning I would suspect it to be in either the transmission or drive shaft - torque tube area.Also would check for possible bent drive shaft.Note that in 1951 they increased the diameter of the torque tube to make it more riged--perhaps its a good time to consider switching drive line and gear ratio in this car.

These cars are very tempermental in this area.I replaced the transmission mount in my low milage 1950 Power Glide recently.After that it developed a vibration above 60 MPH when the trunk was loaded -as when we travel etc...I loosened and repositioned the mount and vibration is now gone.
Replaced the front drive shaft bushing and U joint on my 1939 - vibration improved was was still there...placed the PC clamp on the torque tube slip joint (as Lykmall mentioned) and car is as smooth as glass at high speeds.Seems that there is no single solotion.

For some reason 1949's and 1952's both had the jumping out of high gear problem when new.The cure from Chevrolet was to install the 1953 main drive gear and main shaft with its double row of needle bearings for better shaft alignment.

An out of balance pressure plate will also cause vibration along with the flywheel.....Also wonder if looseness in the rear end of the drive shaft could contribute to it - such as a loose front or rear pinion bearing??just some more thoughts.

Thank you Chevgene for your thoughts on this issue. I hate to think that I might have a problem in the rear end. I believe that the car has between 110K and 115K miles. Is it likely to have a rear end problem with that kind of mileage?

I have two sets of torque tube clamps. One indicates it is for cars made through 1941, the other through 1942. The dates are probably the year of manufacture. I would like to try one on my 50 but neither seems to fit. The torque tube is larger than the clamps and the nut that retains the seal is larger than the clamps groove. Would there be a newer clamp for a 1950 model? Where would you find one? I keep checking Ebay but haven't found one yet. Incidentally, I don't have the installation instructions for these either.

It was not uncommon to require "rear end" repairs on those any time after 50,000 miles.The most common was the front pinion bearing or the side carrier bearings.

Drive shaft clamps....The "clamp" I have consists of two plates.They have a 1/2 round indentation in them and fit over the back of the U joint ball - at the very rear end of it-and extend to the very front of the drive torque tube-the smaller diameter part-before it, the torque tube, expands to "full size'.They are clamped together with 4 or 6 bolts (can't remember) with coil springs holding tension on the plates.Bolt nuts use cotter pins (castel nuts) to prevent loosening.There are several sizes made as the ball and T. tube diameters changed a few times from 1929 and up.I would think that thw 1937-54 would all be the same as they all use the same ball and the front skinny part of thr torque tube were all 2".The rear half was increased in size from 2 13/16 " in 1950 to 3 1/4"in 1951.This was done to "raise the fundamental frequency of torque tube vibration.With this change , vibrations from other sorces no longer combine with that of the torque tube, over a narrow speed range, to produceed peak vibration point which was encountered occasionally in the past".

I drove many of these cars when new - never noticed a difference in vibrations and they did not vibrate noticably when new-by 1950 standards.But for some reason they were refered to as "Janesville vibrators" in this Janesville assembly plant area.

The rear of the drive shaft is supported by the front of the pinion gear - held by the splines.If the splines are worn could this cause a vibration???Sounds like a good car to install the 3.73 gears in that you have.The new parts, combined with the slower turning drive shaft amy make a big improvement.

Guess I'll learn to love the noise. I don't have the skills to do the job myself. I do think that the change in rear end ratio would certainly help. The clamps I have use 6 bolts and 6 springs. They don't seem to fit the torque but maybe I need a bigger hammer.

Thanks for the great suggestions, fellas. I'll pass them along to my friend.
-Bob

Glyn

Do you recall if the vibration on your car was under both coast and drive? Mine is mostly coast. My guess is that your solution is the way I'll have to go.

The car would move out of 3rd gear at 55 or so with the car just cruising on a fairly level road and some times on the down hill with no load. The vibration came in at about 50 again seemed to be with the car just cruising niether pulling hard or on compression.

If under coast usually the U joint or the bushing at rear of transmission that the front yoke of the U joint rides in (not torque tube)...Bushing is available from Chevs of the 40's.....this is assuming that the torque tube bushings are good.I had forgotten to mention this trans. rear extension bushing earlier--this is used only on 1949-54 cars.The U joint front yoke is usually also worn where it rides in the bushing.

Well, both the u-joint and the bushing at the end of the transmission are both new but the u joint may not be GM so it's possible that is the problem. After market products sometimes are not up to GM standards.

I learned that when restoring my '34----some of the old-not brand name stuff-ie.not Thompsom,Sealed Power etc. were junk years ago.Genuine Chevrolet is best if available.

I found my old u joint that I had removed. The trunnions and bushings are very tight. I measured the front end of the u joint and if I measured correct it is 1.435". A new rear transmission bushing measures 1.440". With only .005 play I think that I might put the old u joint back and see what happens.

The new u-joint was made by an outfit called "Pilot". They were located in Chicago. This would be back in the early 70's.

Bowtie Bob

Did you ever find the cause of the vibration?