Closing in on 60 Vibration

[60eldo]

So I was driving today, new rebuilt engine and I still have a slight vib at 15-20 mph then again at 35-40 then it goes away. So I tryed something today. I was on a hill facing down, and as car started rolling down I put it in neutral an shut the engine off. No vibration. Did it again engine running and in drive and vib is back. mmmmm   Is my vib coming from the engine maybe the crankshaft? When I shut it off and rolled whats moving. I no the rear end is, and the driveshaft, but is the trans still turning, and is the engine rotating? HELP this is driving me crazy, 6 yrs of trying to slove this

[Moody]

The engine is not turning. Only the output of the trans is moving. I know some automatics will spin the motor if rolling, but not this one. This problem has been an issue in the past, and there are a few threads on here about it. It's usually related to driveshaft angles.

[60eldo]

 If its the driveshaft angle, then the car should vib when engine if off, but it doesnt

[Clewisiii]

If its the driveshaft angle, then the car should vib when engine if off, but it doesnt

What speed were you going down hill in neutral.

And it is not apples to apples. When the drive shaft is spinning by the engine it is being torqued from engine load and the road. In neutral it has a lot less torque in the system. It has an effect on any vibration.

[60eldo]

I started my speed at 0, then coasted down the hill to 40mph, its vibs at 15-20 and 30-35mph

[dn010]

And it is not apples to apples. When the drive shaft is spinning by the engine it is being torqued from engine load and the road. In neutral it has a lot less torque in the system. It has an effect on any vibration.

Agreed. You can't really diagnose a vibration by coasting down a hill, the only thing you've ruled out is your wheels + brake drum balance that way. It could still be anything in the drivetrain.

[TJ Hopland]

If its the engine you should be able to change the speeds its happening at by forcing it to stay in a different gear.

[60eldo]

  TJ,,,,,WHAT??

[Warren Rauch #4286]

   The June 1960 Roundtable film was "The Critical Angle". It dealt with your problem. It is a little too general to be of much help.But, Message or email me an address and I can send you a photo copy of the hand out.

  Basically  it tells to check for 1) engine vibrations
                              2) out-of balance wheels,tires,brake drums and prop-shaft
                              3)check prop-shaft with alignment tool J-8905
                              4)unlikely-- runout or unbalanced axle shafts,differential carrier,  internal transmission (if high speed (55-75 mph)is the problem)

It mentions that coupe styles before engine # 077573,may have the wrong rear springs. The standing height of the rear should be between 5 1/2 and 6 1/2 inches. If over 6 1/2 replace rear springs,before trying to align the prop-shaft. (I'd try the shop manual for how to measure)

A second odd problem is the rear engine mount. 1959 and 1960 mounts and members look the same,but aren't. The 1959 and past models use a soft rubber mount. 1960 it is a hard rubber mount. The members differ because of this.

There is a picture of the parts of J-8905. The gauge blocks do not have measurements. if only someone has a set,they don't look hard to make.

Warren

[TJ Hopland]

TJ,,,,,WHAT??

If its a certain engine RPM that is setting off the vibration if you manually change gears so it doesn't shift in the usual places you will be changing the ground speed vs engine RPM so the vibration should appear at different ground speeds.  I don't remember the specifics of that transmission, I know it acts a little different than the later ones most of us are more used to.

[60eldo]

 I just tryed something maybe I found it. I sat in the car with a RPM meter, in park not moving, I slowly pressed the gas and at 800rpm and then again at 1200 it had the same vib in the steering wheel. Then I drove the car with rpm guage on my lap and guess what. At 15-20mph car vib and meter read 800 rpm. Then at 35mph, meter read at 1200. BTW when I was going 60mph meter read 1700 rpm.. Im thinking now the only things that are turning when car is in park and reving are the crankshaft, harmonic balancer, flex plate, fly wheel, or torque con. Must be one of these

[Clewisiii]

I think my engine is smooth. But I am honestly crossing my fingers on the harmonic balancer. I did nothing with it but clean and paint it.

[Lexi]

For what its worth. I recently had a ton of carb issues. 3 carburetors later, think I got it finally fixed. That said, one carb came back from a rebuilder and after a few days my car developed a vibration. You could feel it in the steering wheel and even see the rear bumper shake a bit at idle. Smoothed out at higher RPMs on the road. Put on another carb and all that vibration suddenly was gone. I have sent that spare carb back to the rebuilder. Clay/Lexi