Packard Forum Index » V-8 (1955-56)

I get lots of consultation calls and yesterday's was about a vibration. The owner rebuilt the engine himself and has checked most everything he can think of.

1. The rotating assembly, including front damper and flex plate were professionally balanced.

2. A replacement torque converter was used, but these are supposedly neutral balanced at the factory and thus interchangeable.

3. Idle is smooth, as engine speed is increased, vibration comes either in park and in gear, greatest around 1800 RPMs and becomes less noticeable at higher RPMs.

The owner's plan of action is to remove the torque converter and run the engine without it to determine if the torque converter could be the problem. If it is, then he'll have it rebalanced.

He's also found a field balancing service which uses equipment similar to the old Hunter or Bear on-car wheel/tire strobe light. They'll come out and set up under the car to try to locate the area of imbalance.

Before either of these expensive services are undertaken, anyone think of anything he's overlooked?

One area I suggested is to start the engine and retard the timing from 10 degrees initial back to zero and see if that changes the vibration.

jack vines

Did the engine vibrate before the rebuild?????

Try a compression check. Also there is some kind of valve lifter bleed down procedure in the SM.

Is the motor in a Packard, 56J, or Nash? Is the vibration most noticeable when sitting in the car, or leaning over the fender? Are any of the motor mounts "bottomed out", or brittle? Are the exhaust pipes "kissing" the frame anywhere? Are the pipes rubber strap mounted, as they should be? If in a 56J, is the generator bracket kissing the fender apron?

Did he have the rods checked for straightness when he did the rebuild?

Can he "feel" the vibration, in synch with his ears, by laying his hand on the motor? If its a 56J, can he feel the vibration, in synch with his ears by putting his fingertips on the headliner?

The TC was likely balanced at the factory. But if anyone has disassembled it during the past 50+ years it may be out of balance. I recall making an alignment mark across both halves, before dis-assembly. If the halves are not reassembled exactly as they were when balanced, it screws up the balance.
So, if none of the aforementioned fix the problem, it may be in the TC.

I once test drove a 56J with Torque-Flight tranny installed, and it had a pretty bad vibration, coming off idle till about 2000 RPM. I hypothesized it was due to the spool adapter being slightly out of alignment, but passed on buying the car for fear that fixing it coulda turned into a can of worms.