Vibration at Speed

[Loyd Smith]

After two years of working on the mechanicals/electrics in the ?55 Pat, she?s purring like a kitten, has plenty of power, stops well and have finally gained enough understanding and experience with the, ?teeter-totter,? principle involved in T/L suspension to get it properly adjusted and working without glitches (after having had control unit converted to solid state). After having got the exhaust system, suspension and body properly isolated from the frame with required replacement rubber and being able to isolate what vibrations, noises, etc were coming from where and eliminating them (new front and rear U-joints, for example, and other things) and replacing the wide whitewall, ?classic,? tires with some that were round, albeit narrow whitewalls, and properly balancing them I now have no trouble cruising the roads comfortably at speeds up to 80 mph.

Lately however I have begun to notice a marked vibration at between about 50 and 55 mph. It is much worse when using the planetary drive side of the Twin Ultramatic than when using the, ?mush,? drive selection and will not go away when in the first, ?Drive,? selection just upwards of, ?Low,? gear. When using the torque converter to direct clutch hookup (second, ?D,? selection up from, ?L?) this seldom occurs, is less severe and will go away, most times, if I let up on power and then re-apply accelerator gently. Am suspecting that I?ve got a problem with the transmission. It is the one portion of the drivetrain that I?ve had no trouble with since acquiring the car. It shifts, in both, ?D,? selections at the advertised speeds depending upon acceleration, almost imperceptibly, does not leak and I?ve never had any problems with it except for it shifting a little hard before I took the pan off, cleaned filter and changed the fluid in it a couple of times. There does not appear to be any direct drive clutch slippage and acceleration is constant with no shudder or chatter after shifting in either drive ? except for the vibration at the above mentioned highway speeds in direct drive. As stated above, this does not occur often when using the torque converter to direct drive clutch, ?Drive,? selection and will go away. When using the two-speed planetary to direct drive clutch, ?Drive,? selection, it will not go away. When it occurs, the vibration lessens somewhat after reaching approximately 60 mph but can still be felt as a vibration.

Any ideas, suggestions or recommendations from any of you more highly experienced ?55, ?56 owners?

[Guest Randy Berger]

If I understand you correctly, Drive-left or "mush" does not vibrate or vibrates much less. When starting out with Drive-right(where the vibration occurs), once you are in direct clutch hookup can you manually shift to Drive-left and have the vibration disappear?

[Packard enthus.]

What makes you think the u-joints you got are any good ? We are getting some really poor quality replacement U joints these days.

Before you do anything else, take your entire drive shaft to a good drive-shaft shop. What about your front U-joint? is that a "standard" type or that goofy "Detroit" type, where the slip spline is nothing more than a pair of rollers?

Have the drive-shaft shop check your drive shaft for balance and "true".

[6219_Rules]

Before you start tearing your suspension and drive link apart, you might check to see if somehow you may have bent a wheel out of round. Driving out to the airport last week, I noticed a marked vibration at about 55-60 mph. My first thought was the drive shaft and 'U' joints, then the bearings, figuring that the modern tire may be rubbing on corners (there is a sound like that). Came to discover, much to my relief, that at some point I ran into a pot hole or speed bump and bent the wheel. It could also have broken the steel belt or gone out of balance. Today I checked it at the Goodyear... bent wheel.

It is not noticable until third or four gear in my '56 Cadillac, so I thought you might check that first. It is simple and cheap. Jack up the car in the rear and put it on jack stands so both wheels are off the ground. Chock the front real well. Then start the car, put it in drive and excellerate it up to 50 or 55... have some one check the rear wheels as they spin to see if they wobble. You can also check the drive shaft and wheel play for problems. Just a thought. Hope that helps.

[Loyd Smith]

Suspension troubles have already been dealt with. Bent wheel (one) and bent hub (one) have already been dealt with. Drive shaft (with, "goofy," Detroit Ball U-joint) has already been checked out and is in balance. Just put new tires on and checked 'em for roundness (one of the new - less than 2000 miles - wide-whitewall radials from one of our better-known suppliers that I just replaced was three-quarters of an inch out of round) and balance, myself, on computerized balancing machine. They're good. This new symptom has showed up since having done all of the above. When I first got the car all of the suspension/steering/body bushings on it were gone, exhaust (what there was of it) was rattling against the frame, kingpins, inserts, idler arm were all shot, engine had one scored cylinder wall, main and rod bearings were shot, carburetor was wrecked (although, to its credit, the old car would still crank and run). First, started with engine and exhaust, then suspension/steering followed by wheels/hubs, etc, I've been conscientiously eliminating mechanical problems and associated vibrations, noises, etc, one at a time as time money and circumstances permit, replacing parts as indicated (I'm PAINFULLY aware of a lot of the junk that is available from some speciality vendors). I am not a novice at this - although probably more years out of practice than some (obviously not all) of you are old and less mentally quick than I once was - so it is possible that I've overlooked something obvious. Randy - I haven't tried shifting as you suggested as yet but will do so immediately.

[Packard enthus.]

I give up - about the only remaining thing I can think of is perhaps your torque convertor "threw" a balancing weight.... ? ? ?

[Guest 1956Packard]

Balance the tires on the car.....?

[Loyd Smith]

Randy - Tried shifting from planetary to, "mush," drive and vibration does go away/becomes almost completely unnoticeable. Haven't been driving the Packard too much this past week or so but, seems markedly improved at speed (55-70 mph) as long as I don't use the planetary drive selection. Do not seem to have any out of round/unblanced tires/wheels.

[Guest Randy Berger]

Glad you got back to us Loyd. I suspect dirt or a gummy valve that is not releasing/applying pressure when the manual valve is in the Drive Planetary position. Try contacting Ultramatic Dynamics and see if he has any suggestions.

I wish I could offer a better immediate suggestion. Please keep us informed.