Buick Engine >> BALANCE SHAFT & CRANKSHAFT COMBINATIONS

Buick Engine >> BALANCE SHAFT & CRANKSHAFT COMBINATIONS

Balancer Assembly and Crankshaft Combinations On
GM 2.5L (VIN U) Engines

General Motors has provided the remanufacturing industry with another challenge when it comes to assembling GM 2.5L engines with balancer assemblies.
The balancer assembly first appeared in 1987 GM N body vehicles equipped with manual transmissions, such as the Pontiac Grand Am and Buick Somerset. This engine uses a crankshaft with the casting number 10044390. This crankshaft gear features 82 teeth while the driven balancer gears have 41 teeth.

Some OE parts books may list 625 as the casting number for the 1987 model year crankshaft. To-date AERA members have been unable to find crankshafts with this casting number.

Vehicles with VIN Code U engines may also use a crankshaft with the casting number 10044406. Unfortunately, there are two versions of this crankshaft. One version has a 78-tooth gear, which mates with 39 tooth balancer gears. The other version still uses 82 teeth and requires a 41-tooth balancer assembly.
Vehicles with VIN Code U engines manufactured for 1988 model year vehicles should only use casting number 1000406 crankshafts with 78 teeth.

Using the wrong combination of crankshaft and balancer assembly has caused complaints ranging from significant noise in the lower end of the engine, to premature engine failure. AERA members have reported 2.5L truck engines equipped with crankshafts that have a balancer drive gear although a balancer assembly is not used in this application.

For additional information see AERA Technical Bulletins: TB 778. 720, 690R & 511.
The AERA Technical Committee

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