One of the leading complications vehicle owners encounter with their engine is crankshaft thrust bearing failure. This is often a contentious predicament if this takes place, particularly if the failure occurs in a recently rebuilt engine. Many vehicle owners are quick to lay the blame on the engine builder or maybe a failed internal engine component. However, in most instances thrust bearing failure isn't related to the engine whatsoever.
For starters, it is essential to understand what the purpose of a crankshaft thrust bearing is made to accomplish. In general, the thrust restricts crankshaft endplay. By eliminating almost all the forward and backward motion of the crankshaft, close tolerances can be preserved in the complete rotating assembly. Especially at high revolutions, this is extremely critical to maintain the life of the engine.
While it is possible that a recently rebuilt engine can have a misaligned main cap and related bearing, the much more likely culprit is a bad torque converter. The torque converter is designed to push against the crankshaft. Under normal circumstances the amount of forward torque converter pressure is minimal. But when transmission oil exceeds normal running temperatures, the internal pressure in the torque converter greatly increases. Due to the increased pressure, more frontward pressure is placed on the crankshaft. This is definitely the primary root cause of crankshaft thrust bearing damage in vehicles running automatic transmissions.
Whenever a crankshaft thrust bearing fails in a stick shift vehicle, typically the problem is either the result of incorrect throw out bearing adjustment or bad driving practices. Whenever drivers ride the clutch, this places extra frontward force on the crankshaft and can cause the bearing to become damaged.
Out of alignment accessories that are installed on the front of the engine may also result in crankshaft thrust bearing failure. However, this generally only occurs in performance vehicles that have belt driven blowers or other components that are designed to maximize horsepower.
By taking a look at a crankshaft, that has a failed thrust bearing, either the front or rear thrust surface will be badly damaged. In the event the rear thrust is damaged, the harm was most likely caused by the torque converter. In the event the crankshaft damage is at the front thrust surface, then an improperly adjusted accessory is usually to blame.
In the engine building industry, damaged crankshaft thrust bearings are very prevalent. And while many vehicle owners may fault the engine for the damage, in many instances either excessive transmission oil operating temperatures are at fault or bad driving practices in cases of vehicles which have a manual transmission. Crankshaft thrust bearing failure in most instances can be averted by better driving habits or by adding a transmission oil cooler in automatic transmission cars and trucks.
Nov 20, 2011
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