one Car Two Personalities 1957 Cadillac

[Bill Balkie 24172]

Hello,
  Maybe someone can help.  I drive my car on an average of one to two times  a week .  The car is a 1957 Cadillac Eldorado Biarritz  365 C.I. with the original rebuilt carter Carbs 2X. The car starts right up every time without any issues .The car is a pleasure to drive most of the time .Very smooth strong acceleration  very comfortable . However every now and then it develops rumbling of some type .feels like maybe the tires have flat spots or the drive shaft is out of balance . it is very hard to understand because it does not have this condition all the time .Today I drove the car  to a show for a distance of 25 miles. smooth as silk . On the way home I developed the rumble for lack of better words . The engine temperature  is fine .Does not run hot .This can happen with the car  hot or cold . when this does happen I tried putting the car in neutral  doing about 30 miles an hour .Revved the mother smooth as silk however the rumbling is still there while coasting .I have radial tires  tried increasing the tire pressure but it does come back .I had my front wheel  bearings replaced .What puzzles me is  how can this happen every now and then .In my way of thinking  a drive shaft is out of balance or is balanced ,same with wheels or bearings . The car is not starving for gas . I thought I was getting this rumble with the  back windows up while driving causing some type of turbulence .could it be in the transmission ? 70 percent of the time it is smooth as silk ,30percent  I have a rumble . I had a 57 Seville  that had  a sort of a rhythmic  type of a rumble at 45 to 55 miles per hour and that was a drive shaft out of balance .I have to get to the bottom of this  . Any help would be greatly appreciated .   Bill

[Bobby B]

Could be anything. I would start by checking each tire on a high speed balancing machine first. Lately, they have a tendency to go from the inside out. Eliminate that possibility and then go from there. The problem today with parts is that most of them are garbage. Easy to get a brand new, in the box, bad wheel bearing. Keep us posted.
                                                                        Bobby

[savemy67]

Hello Bill,

Your car is 59 years old.  As Bob said, it could be anything, including the transmission.  What on the car has been completely rebuilt?  How long have you owned the car?

Is the rumble audible only, or do you feel the rumble?  If you feel the rumble, do you feel it through the steering wheel, or through the body?  Does a reflection in the rear-view mirror rotate?

An intermittent problem might indicate a failing component.  You can chase a dozen wild geese trying to find your problem, or wait until something more specific occurs, and then follow-up, provided you do not compromise safety.

Respectfully submitted,
Christopher Winter

[Bill Balkie 24172]

Could be anything. I would start by checking each tire on a high speed balancing machine first. Lately, they have a tendency to go from the inside out. Eliminate that possibility and then go from there. The problem today with parts is that most of them are garbage. Easy to get a brand new, in the box, bad wheel bearing. Keep us posted.
                                                                        Bobby

Hello Bobby ,I have to start somewhere . I think if it were the wheels it would be constant all the time 100%.It almost feels like the engine is missing . very hard to understand because it comes and goes . I think I will start with a good tune up and get all 4 wheels balanced . The tires are about 8 years old B.F. Goodrich Wide white Radials .With plenty of tread .and get the wheel bearings checked out again . I Will  let you know how I make out

[Jon S]

I'm thinking it could be a failing motor mount or transmission mount since it is so intermittent.  They are easy enough to check.

[Bill Balkie 24172]

Could be anything. I would start by checking each tire on a high speed balancing machine first. Lately, they have a tendency to go from the inside out. Eliminate that possibility and then go from there. The problem today with parts is that most of them are garbage. Easy to get a brand new, in the box, bad wheel bearing. Keep us posted.
                                                                        Bobby

Hello Bill,

Your car is 59 years old.  As Bob said, it could be anything, including the transmission.  What on the car has been completely rebuilt?  How long have you owned the car?

Is the rumble audible only, or do you feel the rumble?  If you feel the rumble, do you feel it through the steering wheel, or through the body?  Does a reflection in the rear-view mirror rotate?

An intermittent problem might indicate a failing component.  You can chase a dozen wild geese trying to find your problem, or wait until something more specific occurs, and then follow-up, provided you do not compromise safety.

Respectfully submitted,
Christopher Winter

Hello Christopher , All good questions .I have owned the car for 5 years . I feel the rumble I do not hear it . does not come thru the steering wheel .  It feels like something is loose .   like the car is not rolling freely .  Even when I take it out of gear and coast at high speed ( 35  to 50 ) in  neutral I hear a rumble . Most of the time it drives like a brand new car very smooth . Thanks Bill

[Bobby B]

Bill,
Hi. If you're coasting in Neutral and you still hear a rumble, it's obviously in a ROLLING part of your drivetrain, not a DRIVEN part. Does the sound drop in pitch when you put it in Neutral or stay constant with the speed you're at?  I was going to take another guess at a possible weak U-joint until you said that, but I can't rule that out yet. A bad Torque converter will also do that, but the pitch will vary at different speeds. I'm now leaning towards a rear axle, worn gears, etc. Whine or rumble in coast usually involves the rear end. When was the last time you checked the fluid, and did you ever check it since you've owned the car? Most people never even think of checking a rear when doing anything. They just think it lasts forever. Popping the cover off the rear wouldn't be a bad idea. You can see the pattern between the ring and pinion gears once it's open. Noises that come and go are time consuming to detect. Stay with it, you'll get to the bottom of it.
                                      Bobby

[Peter Nieuwlandt]

Bill,I had something similar on my 56 convertible,I replaced the rear axle bearings and all seals and that solved it .
When i got the bearings out and I turned them you could hear a sound.
Also some time ago on a 1958 Corvette i had something similar,that time it turned that the center nut of the yoke with goes  into the rear axle worked itself loose a few threads…..
I just tightened it with and the problem was saved.
As someone already said in this thread,most collectors forget to look after the rear axle although it very important.

Hope this helps

Peter

[dadscad]

If your car has a two piece drive shaft, I would check the center support and bearing.

[Bill Balkie 24172]

If your car has a two piece drive shaft, I would check the center support and bearing.

Thanks I did replace that mid bearing

[Bill Balkie 24172]

Bill,I had something similar on my 56 convertible,I replaced the rear axle bearings and all seals and that solved it .
When i got the bearings out and I turned them you could hear a sound.
Also some time ago on a 1958 Corvette i had something similar,that time it turned that the center nut of the yoke with goes  into the rear axle worked itself loose a few threads…..
I just tightened it with and the problem was saved.
As someone already said in this thread,most collectors forget to look after the rear axle although it very important.

Hope this helps

Peter

Thank you , very good advice . I think I will have the rear end looked at this week . we keep you informed . Thank you all so much