1966 Idler Arms

[Peter M.]

The 1966 JM calls for two different idler arms - one for manual steering (3779185) and one for power steering (335GMT3779185B) - What is the physical difference between the arms ? I have a maunal arm on my PS car and am not aware of any issues.

[Joe L.]

Re: 1966 Idler Arms

Peter------

My personal opinion is that different idler arms were NOT used in PRODUCTION on power steering versus non-power stering cars, although different forging numbers for the idler arms may have been randomly used and some folks have ascribed these different numbers as being applicable to power steering and non-power steering cars.

In PRODUCTION, there was only one idler arm PART NUMBER ever used for 63-81 Corvettes. That PART NUMBER was GM #3779184. This piece carried forging number 3779185 on the forged arm. However, it was NOT the only idler arm that carried this forging number on the forged arm. GM PART NUMBER #3817956, which was the idler arm used for some 1963 light trucks, also used the same arm with forging number 3779185. However, for this arm, the vertical, frame-mount component of the arm assembly was different and is not, as an assembly, usable for a Corvette application.

I think that the different forging numbers seen on some original Corvette idler arms, especially the "3779185B" was a method used in PRODUCTION to differentiate and identify the Corvette arm from the truck arm. For whatever reason, it was not used consistently throughout production, but I think that's the reason for the different forging numbers and NOT the p/s versus non p/s issue.

[Peter M.]

Re: 1966 Idler Arms

Joe
That help solves the mystery for me as to why every 1966 I have looked at in the past 3 years whether PS or Manual had the same idler arm #. Perhaps this information will find it's way back to an amended 1966 NCRS judging manual. I will check that out. Thanks
Peter

[Mike M.]

Re: 1966 Idler Arms

joe: did the truck idler arms have or lack the grease fitting? mike

[Joe L.]

Re: 1966 Idler Arms

Mike-----

The truck arms did not have any grease fitting. I have a few of them [none for sale, but who would really want them, anyway?]

[Mike M.]

Re: 1966 Idler Arms

joe: does the early 60's chevy truck idler arm have an offset(about 1/2 inch) in its piece that attaches to the frame of the truck(as opposed to a flat bracket that attaches to the c-2 vet frame. thanks, mike

[Mike M.]

Re: 1966 Idler Arms

PS joe. went to barn, got my stash of idler arms, wire brushed the used ones i've picked up at carlisle over the years and here's what i have. Six of the used nonZerk fitting idler arms have the following forging #s in the forged arm 3779185 with a 2 1/2 " gap then GM forged near the pivot end of the arm. One of the used idler arms has the following forging data: 237 GMT 3779185A. note reversal of # and GM logo on the two different idler arms. Must have been different suppliers, huh? regards, mike

[Joe L.]

Re: 1966 Idler Arms

Mike-----

Yes, the truck arm has a 1/2", or so, offset on the frame bracket which is unlike the Corvette piece.

The idler arm with the "GMT" forging mark was forged at the GM Tonawanda forge (now part of American Axle and Manufacturing Corp.). The others may or may not have been forged there using different forging dies. These arms were manufactured over a period of about 20 years, so many different forging dies may have been used. Whether or not these arms were also forged at other locations or by other non-GM entities, I don't know.