NOS Idler Arm vs Factory Original

[Edgemontvillage]

I just purchased an NOS idler arm for my '69 Z. I have read there are some differences between the factory originals and NOS service replacements however the part I received was "missing" the cotter pin hole which struck me as a manufacturing defect. I was later told that NOS idler arms used an oval locking nut rather than the common castellated nut and cotter pin combination. Can anyone validate this observation?










 

[WorkinProgress]

Takes an 18 mm prevailing torque nut. Uses no cotter pin. Was the last design idler arm. GM part number 14083585 Group 6.895

                                                                                                 - Warren

[69Z28freak]

Takes an 18 mm prevailing torque nut. Uses no cotter pin. Was the last design idler arm. GM part number 14083585 Group 6.895

                                                                                                 - Warren

I tested the thread on this idler arm and it is a 12 mm coarse thread.

[ZLP955]

Lloyd does the NOS idler arm have a 'C' or an 'O' stamped in between the 2 frame mounting holes?

[Hans L]

Here's a close-up of the idler arm from my Z (04B, Van Nuys Build).   Note hole for cotter pin and "C" stamp.  Car had about 70,000 miles on it, all SoCal.  No reason to believe it or any suspension components were replaced (many still had original factory markings).

[Edgemontvillage]

Lloyd does the NOS idler arm have a 'C' or an 'O' stamped in between the 2 frame mounting holes?

The NOS arm isn't stamped on either side of the bracket that bolts to the frame.

[68camaroz28]

Our 68Z has an "O" stamped idler arm.

[67rs/ss350 68z/28]

My 04D 68Z has the letter "C" stamped idler arm

[1968 Z28]

My 1968, 07C, Z28 has a "C".

[Boston14]

My 1969, 11D (68) SS has a "C".

[Edgemontvillage]

Thanks for the feedback and photos. Its clear the NOS Idler Arm I located is a later, service replacement and differs somewhat from the factory original.  I located a nice original and installed that instead.