Vibration in the 1800 RPM range - thoughts or suggestions

Posted by Jack Vines On 2014/1/1 18:21:13

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