Hello,I have a 1994 FRT 120 that has a 3406 cat engine. The truck developed a vibration about a month ago. The Kenworth dealer changed all of the U-Joints but the vibration was still there only when loaded. I took the truck back to them and they completed an overhead (adjusted valves only) and now the condition is worse. I feel the vibration all the time now, loaded or empty. Any ideas?? Thanks for your help.
Model: FL 120
Engine: 3406 - 425 hp
overhead, new u-joints
Hi. Thanks for using JA! I will try and help you out.
Most often when a vibration begins on a truck, I first suspect the vibration dampner on the front of the engine has failed. Especially if it has a 2 piece dampner. The tough part is the only way to know if to replace the dampner itself. If you are lick y enough to have another truck that you can swap the dampners on, that is a great idea. If not, the only option is to replace it with a new one.
I the dampner is not the problem, I would next suspect the clutch. I see this from time to time. If yo are able to fell the vibration by reving the engine up to high idle, you can have the transmission removed and the clutch assembly removed, and then run the engine. If the clutch is the problem, you will see the vibration go away.
Please reply back if you need more help.
23 Years Caterpillar Engine experience.