Idler Arms 3917581A vs 3917581B
 

I have a couple of original 69 Idler Arms here and wondering the significance in the 2 different part numbers? Can anyone with knowledge chime in on this?

3917581A = Heavier Beefy looking Idler Arm
3917581B = Lighter narrower beam Idler Arm

Are they both either manual or power steering? One is lighter than the other in terms of beam thickness?

Here are a couple picture of the two idler arms. The beefier one with the heavier forging is 3917581A and the smaller diameter forging is the 3917581B. Both measure out the same length and same height so it appears it's a difference in the beam thickness and perhaps the strength of one over the other?

One is for power steering and one is for manual steering?

https://i.ibb.co/Tc9rMNW/IMG-2780.jpg

https://i.ibb.co/J3ZkqCJ/IMG-2782.jpg

The thinner idler arm was standard on all '69 Camaro's and Nova's. Not sure when they changed it to the beefier arm but my guess is around 1971. I believe the '70 Nova's used the same thin idler arm.

Manual or power steering used the same arm.

Sometime around the late seventies or early eighties they made a change to the beefier idler arm. It came with a metric torque nut and no cotter pin hole.

- Warren

If u look at my build thread under idler arm our 68z had the 3917581a.

Thanks Chick,

This one came of a low mile car that was restored. It's very clean and I will be using it over the skinnier B version. Love that 68 of yours and thanks for making reference points so easy with your list. It's like point and click. :)

Cheers...Graeme