Crankshaft Thrust Failure Explained

One of the leading complications vehicle owners experience with their engine is crankshaft thrust bearing failure. This is sometimes a contentious predicament when this happens, especially if the damage occurs in a freshly rebuilt engine. Many vehicle owners are fast to lay blame on an engine builder or even a failed internal engine part. However, in most instances thrust bearing failure is not linked with the engine at all.

First, it is essential to know what the purpose Crankshaft Grinding of a crankshaft thrust bearing is made to do. In general, the thrust restricts crankshaft endplay. By eliminating the majority of the forward and backward motion of the crankshaft, close tolerances may be preserved within the total rotating assembly. Especially at high RPM’s, this is very important to preserve the lifespan of the engine.

Even though it is possible that a freshly rebuilt engine might have a misaligned main cap and attached bearing, the more likely culprit is a bad torque converter. The torque converter naturally pushes against the crankshaft. Under normal operating conditions the level of forward torque converter pressure is minimal. But when transmission oil is greater then normal operating temperatures, the internal pressure in the torque converter greatly increases. Because of the increase in pressure, more frontward pressure is applied to the crankshaft. This is by far the main reason behind crankshaft thrust bearing problems in vehicles running automatic transmissions.

Whenever a crankshaft thrust bearing fails in a stick shift vehicle, typically the problem is either the consequence of poor throw out bearing adjustment or poor driving practices. Whenever drivers ride the clutch, this applies added forward force on the crankshaft and can cause the bearing to fail.

Out of alignment components that are mounted on the front of the engine can also cause the crankshaft thrust bearing damage. However, this ordinarily only occurs in high performance cars that have belt driven blowers or other parts that are designed to boost horsepower.

By looking at a crankshaft, which has a failed thrust bearing, either the front or rear thrust surface area will probably be badly damaged. In the event the rear thrust is damaged, the harm was most likely a consequence of the torque converter. When the crankshaft damage is on the front thrust bearing surface, then an improperly adjusted accessory is probably responsible.

In the engine building industry, damaged crankshaft thrust bearings are very common. And even though many vehicle owners may fault the engine for the damage, in many instances either excessive transmission oil operating temperatures are at fault or poor driving habits in cases of vehicles that are equipped with a manual transmission. Crankshaft thrust bearing failures in many instances can be prevented simply by better driving habits or the addition of a transmission oil cooler in automatic transmission automobiles.

Jeff is an ASE Certified engine machinist and is responsible for crankshaft reconditioning at his automotive machine shop. In addition to performing machining operations on crankshafts, he also reconditions other essential components which are used in performance engines.

One of the leading complications vehicle owners experience with their engine is crankshaft thrust bearing failure. This is sometimes a contentious predicament when this happens, especially if the damage occurs in a freshly rebuilt engine. Many vehicle owners are fast to lay blame on an engine builder or even a failed internal engine part. However,…

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