1963 Thunderbird vibration

Hello,

I have a vibration in my 1963 Thunderbird.

We have balanced the tires, balanced the drive shaft, checked all the wheel bearings, checked harmonic balancer.. and we still have the vibration, which gets more pronounced as speed increases and it quickens when releasing the gas pedal and coasting at higher speeds.

Although the transmission was rebuilt during the cars restoration...1-1/2 years ago...We’re starting to think the transmission may be the culprit.

Does anyone have any experience with this type of a problem?

Thank you,
Buzz G.
 
Since you balanced the driveshaft I assume you also changed the 'U' joints. A bad one will cause that exact problem. Other than that I would still concentrate towards the rear end. Bushings and other connections. The only other thing I can think of would be motor mounts.
 

Poppy Red

Active Member
I had a vibration on a '66 with the 390 engine. Came in about 2500 rpm, just before shifting from 1st to 2nd. then again, about 45-50 mph. It would also vibrate going downhill with the transmission in neutral and engine idling.
I could replicate the vibration with the car parked, transmission in Park, and raise the rpm to 2500. So, the deductive reasoning was that is was in the rotating parts, which were the engine and the torque converter. Had the torque converter replaced, that moved the vibration from 2500 to 2800!

As you did, I then had the wheels checked and re-balanced, drive-shaft balanced, (with the new universal joint), had the harmonic balancer checked and balanced. had the rear springs re-sprung, as some said the angle of the driveshaft to the rear end could cause a vibration. Checked the motor mounts to ensure they were not faulty, disconnected the belts from AC compressor, alternator, and water pump, no belt driven accessories from the engine, and still a vibration at the same rpm, with the trans in park. I wasn't about to have the engine removed, rebuilt and balanced, due to the cost.
In the end, I could not find the cause, got disgusted, and sold the car. I thought it was an oddity with that car.

I now have another 66 with the Q code 428 engine. and guess what! A vibration around the same rpm. Not as severe as the first car, but annoying all the same. I am presently replacing a broken rear transmission mount, and wonder, if that will solve the problem. Other than that, I have come to suspect the it is a "Ford" fault, and I may not ever find the cause. Again, no plans to have the engine rebuilt and balanced.

Good luck with your vibration. If you find a cause, please do let me know!!!

Cheers
 
How were the rear wheel bearings checked? Was the differential raised and the car put in gear and one wheel stopped and then the other? Is the bushing at the back of the tranny worn and allowing the driveshaft to whip slightly?
 

Poppy Red

Active Member
How were the rear wheel bearings checked? Was the differential raised and the car put in gear and one wheel stopped and then the other? Is the bushing at the back of the tranny worn and allowing the driveshaft to whip slightly?
To Ctitterpainter:

Your questions on the rear wheel bearings or rear transmission bushing could have some effect, (if they were that bad) on a vibration, but it does not explain why I could get the vibration with the transmission in park and no rolling mechanisms in play!
 

64ZCODE

Well-Known Member
Have you checked motor compression? A low cylinder causes vibration at idle and could cause vibration at speed when the engine is under load.
 

Poppy Red

Active Member
Have you checked motor compression? A low cylinder causes vibration at idle and could cause vibration at speed when the engine is under load.
I did check the cylinder compression, put in new spark plugs, checked all the wires, installed a re-built carb to ensure there were no fuel issues causing the vibration. As well, the engine started on the first crank, no misses, and ran very well, no stumbles or rough spots during acceleration. The other thing that mystifies me and all who have commented on this problem, is the fact that it always occurs at the same rpm. Up to the 2500 range, the engine/car runs as smooth as can be.
 
I forgot the small detail that you had the vibration in park. I am racking my brain as when I was in my 20's, my mom had a 65 390 Bird, My dad had a 65 pickup with a 352 stick and I drove a 66 Bird convert with a 428. We also had a 66 galaxy with a 352. I think moms bird had a light vibration under partial throttle that was "the nature of the beast" My bird I can't recall, the pickup always chattered a bit in reverse and the galaxie was so quiet that one did not know if the engine was running or not. That car we bought new.
Could the motor mounts be compressed or rotted to the point that they are no longer effective? or the exhaust system binding as the engine revs?
 

Poppy Red

Active Member
Pretty much "none of the above!" The motor mounts were checked, and there were no noises or rattles from the exhaust or anything else, for that matter.
No noise or rattles from anywhere on the car, just the vibration.
What is mind-boggling is that I thought I had said good riddance to the vibration when i sold the car, (1st one) and was flabbergasted when I have a similar, tho not as pronounced vibration at roughly the same rpm on the 2nd car, with the 428. I have just had the rear transmission mount replaced, along with new front control shafts, bushings and shocks, and that has seemed to have reduced the vibration on this car. Haven't driven it enough yet at higher speeds to have a definite answer.
 

Poppy Red

Active Member
Could it be the flywheel is out of balance?
Thought about that, removed the lower inspection cover, and rotated the flywheel. No sign of where a weight might have been and got thrown off. No teeth missing or any damage. Again, what is the likelihood of two different engines having a flywheel out of balance?
 

Poppy Red

Active Member
Well, surprising as it may seem, replacing the broken rear transmission mount on my present car solved 80% of the vibration. Now, only a kind of a rolling harmonic between 40 and 50 mph.
Suggestion to paxeagle, have you checked your rear transmission mount?
 
Well, surprising as it may seem, replacing the broken rear transmission mount on my present car solved 80% of the vibration. Now, only a kind of a rolling harmonic between 40 and 50 mph.
Suggestion to paxeagle, have you checked your rear transmission mount?
Check your tires. I used to sell Goodyear tires and I found a few that had issues at certain speeds that didn't show up on the balancing machine unless you looked at the tread as it was rotating at a slow speed. Sometimes the tread would wiggle and it would only show up at certain speeds when on the car. That is especially if it only occurs in a range of speed. Go faster it goes away slower, it goes away. I also want to add that in many cases the bead was not seated equally around the rim.
 
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Poppy Red

Active Member
Check your tires. I used to sell Goodyear tires and I found a few that had issues at certain speeds that didn't show up on the balancing machine unless you looked at the tread as it was rotating at a slow speed. Sometimes the tread would wiggle and it would only show up at certain speeds when on the car. That is especially if it only occurs in a range of speed. Go faster it goes away slower, it goes away. I also want to add that in many cases the bead was not seated equally around the rim.
Good suggestion, but not applicable in my case. I put new equivalent OEM size radials on, and had them carefully balanced. Also removed the wheel discs and ride tested it in case there was an imbalance in the wheel discs!! Also rotated front wheels to the back and back to front.
 
Whats the frequency of the vibrations? High frequency indicates drive line issues while lower frequency indicates wheels.
As it varies with load I would check drive line angles. A tired set of leaf springs could allow spring-wrap and if a car is lowered by removing
leafs in the springs it could be even worse
 

64ZCODE

Well-Known Member
Hi Poppy Red. My understanding is a '66 should have a flexplate, not a flywheel. Flywheels were used on manuals, flexplates were used on automatics. If it is a flexplate, is it broken or bent? If it's a flywheel, then it seems someone replaced it in the past and balancing would be something to look at.
 

Poppy Red

Active Member
Hi Poppy Red. My understanding is a '66 should have a flexplate, not a flywheel. Flywheels were used on manuals, flexplates were used on automatics. If it is a flexplate, is it broken or bent? If it's a flywheel, then it seems someone replaced it in the past and balancing would be something to look at.
The '66 390 engines had flywheels. The 428's had a semi-flywheel, (flex-plate) with triangular cut-outs in it. I know this from research done when I got my 2nd car with the 428, and there was some concern that the motor had been changed. It is in fact a 428 with the cut-outs, and there really isn't enough mass (I don't think) to cause the imbalance or vibration I am getting. As I have explained in previous posts, the vibration only occurs about 25 -2800 rpm (40 - 50 mph) I have done many miles of road testing with various situations, and one that more or less eliminates a torque converter or flywheel imbalance is when going down a substantial hill, I can put the car into neutral, let the engine rpm drop to idle, and the vibration is still there. On the previous car, I had the driveshaft with new universal joints and the harmonic balancer checked and re-balanced. Didn't make any difference. On this car I have not had that done. The fact that the vibration is still there going down hill with the trans in neutral and engine idling at the 50 mph speed would seem point to the bits that are rotating. I have eliminated wheels and tires, no problem with with diff, as I had it rebuilt a few months ago, new bearings (wheels included) and a new crown and pinion. That only leaves the drive shaft and universals. Again, I think it is unlikely that the drive-shaft with such a small rotating arc/area would produce the vibration I have. Anyway, it is getting to the point where I have exhausted everything I can think of as well as suggestions from other members and no solution. I am beginning to think it is "Ford" weird event, since I have had 2 different cars, different motors and the same problem at almost the same rpm!!!
Cheers
 
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