As some of you may know, the idler arm used for 1963-1981 Corvettes was GM #3779184. This piece carried the forging number "3779185" on the arm section. So, when some folks see this number on an NOS idler arm, they salivate at the prospect of acquiring an elusive NOS, original idler arm for their car. The problem is that the Corvette idler arm PART number described above was NOT the only idler arm which used the "3779185" arm forging. Some 1963 Chevrolet series 10 trucks also used an idler arm that used this same component with the same forging number. The finished piece was GM #3817956, though, and the truck part is ABSOLUTELY NOT interchangeable with the Corvette part. Unfortunately, the part numbers for the finished pieces appear nowhere on the idler arm assembly unless the original GM parts tag happens to still be in place. Usually, they're not.
So how does one tell the difference? It's simple. The Corvette idler arm assempbly has a frame bracket section with a single offset. The truck piece has a bracket section with DOUBLE offsets. They can be told apart at a glance.
So how does one tell the difference? It's simple. The Corvette idler arm assempbly has a frame bracket section with a single offset. The truck piece has a bracket section with DOUBLE offsets. They can be told apart at a glance.
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