First Order Engine Speed Related Vibrations
IMPORTANT: Anything that is out of balance will only cause a first order vibration, never any higher order vibrations.
First order engine speed related vibrations are unusual on most engines. Only inline 3 and 5 cylinder engines, and V-6 engines without counterbalance shafts have a normal first order vibration. Most first order engine vibrations are caused by an out-of-balance or out-of-round component that is rotating at the same speed as the engine's crankshaft.
Notice: Some engine speed related vibrations are normal; however, they should not be felt in the passenger compartment. Click here to see which vibrations are normal.
On engines that do not have a normal first order vibration, the following components can cause a first order engine speed related vibration.
On engines that do have a normal first order vibration, the following components, if defective or misadjusted, can allow the vibrations to be transferred into the passenger compartment.
Crankshaft vibration dampers are designed to reduce torsional vibration, the small but sometimes dangerous angular oscillations a shaft undergoes, as the alternately ignited cylinders deliver torque spikes to the crankshaft through the pistons and connecting rods. Crankshaft torsional vibration is inherent in all internal combustion engines and can be especially harmful if the damper is defective or damaged. Dampers can be designed to include a counterweight, or in some similar way permit the balancing of an engine if it is not internally balanced, but the damper itself does not balance the rotating assembly, the counterweight does.
Check for cracks, missing bolts, incorrect length bolts, and buildup of dirt and grease.
Check for cracks, damaged teeth, missing bolts incorrect length bolts, missing weights, and correct part for the application.
Check for cracks, damaged teeth, missing bolts, incorrect length bolts, missing weights, and correct part for the application.
Check for missing bolts, incorrect length bolts, and physical damage.
Check for missing bolts, incorrect length bolts, alignment marks with flywheel should be aligned.
Depress the clutch pedal to see if the vibration changes or goes away. If it does, the clutch disk or transmission input shaft may have a problem.
Inspect the disk assembly for damage and missing parts.
Not much to check here except the repair history of the vehicle. Has the engine or crankshaft been replaced? If so, maybe the flexplate or flywheel is incorrect for the new engine or crankshaft.
Check the balance shaft timing to insure correct counter-balancing.
Inspect for missing dampers. Inspect existing dampers for cracking, damage, looseness, and filling with dirt.
Check for grounded out or damaged mounts. This can be done easily by watching the vibration amplitude difference on each side of a mount with the EVA. Place the EVA's sensor on each side of the mount. On a good mount, the amplitude will be higher on the engine side of the mount and lower, if not totally gone, on the frame side of the mount.
Check for grounded out mounts, mounts filled with dirt, or damaged mounts. This can be done easily by watching the vibration amplitude difference on each side of a mount with the EVA. Place the EVA's sensor on each side of the mount. On a good mount, the amplitude will be higher on the transmission side of the mount and lower, if not totally gone, on the frame side of the mount.
Check for grounded out exhaust pipes, rubber mounts that have been replaced with solid mounts, and spring-loaded bolts on flexible exhaust couplings that have been replaced with solid bolts. This can be done easily by watching the vibration amplitude difference on each side of a mount with the EVA. Place the EVA's sensor on each side of the mount. On a good mount, the amplitude will be higher on the exhaust pipe side of the mount and lower, if not totally gone, on the frame side of the mount.
Check for collapsed, grounded out, or damaged mounts. This can be done easily by watching the vibration amplitude difference on each side of a mount with the EVA. Place the EVA's sensor on each side of the mount. On a good mount, the amplitude will be higher on the frame side of the mount and lower, if not totally gone, on the body side of the mount.
If the vehicle has a two-piece or three-piece propshaft, check to see if the front piece of the propshaft has a slip yoke which has been inserted too far into the transmission or transfer case (see image on the lower left). If so, the lack of slip-joint movement can cause a binding in the powertrain mounting allowing normal engine vibrations to be transferred into the passenger compartment. loosen the center propshaft support bearing and slide the propshaft rearward to allow for some slip joint movement (see image on the lower right).
Make sure no hose contact the bulkhead or inner fenders where it should not contact.
Check to see if the mounts for the running boards are bypassing the body mounts (see if the running board mounts to both the body and the frame). Disconnect the mounts to eliminate the running boards as a possible cause of the vibration concern.
Check to see if items like the throttle cable, wiring harnesses, fuel lines, brake lines, transmission dipstick, transmission cooler lines, etc. are making contact with the powertrain (engine and transmission) and the frame or body.
This page was last modified Thursday, March 05, 2009 09:02:44 PM
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