Pitman arm nut and socket size

[Gary B.]

Gary

[Edward J.]

[Gary B.]

[Gary R.]

Re: Pitman arm nut and socket size

The original nuts are thinner then new ones. I use 1 5/16 socket on all of them without a problem. I always install a new nut and torque them to 145-150ft/lb with new lock washer. I will check both new and original when I go back out to my shop and let you know the dimensions.

[Gary B.]

[Alan D.]

Re: Pitman arm nut and socket size

Although not for 66 (it's a Mar64) mine has never been off, measures 1.34

[Gary B.]

[Alan D.]

Re: Pitman arm nut and socket size

1.323 - need to zero first And lots of blackout on it still which I believe GM used.

[Gary B.]

Re: Pitman arm nut and socket size

Akan,

Counting the layer of paint, it sounds like you have the proper sized nut.

Gary

[Gary R.]

Re: Pitman arm nut and socket size

I checked an original 7/8-14 nut and a new one I use as well as the 1 5/16 3/4" drive socket I use.

original nut= .439 thick, 1.305 hex across the flats
new nut= .500 thick, 1.305 across the flats
socket - 1.350 between flats, I don't have a metric socket to compare but never had a problem torquing the nuts.

Then I checked the nut on an original 68 box I am starting on today- same size as the original nut I previously checked.

[Gary B.]

Re: Pitman arm nut and socket size

Gary,

I assume your new nuts are not from Long Island Corvette?

Gary

[Gary R.]

Re: Pitman arm nut and socket size

They are not from LICS, they are standard plated 7/8-14 nuts.

[Gary B.]

[Joe L.]

Re: Pitman arm nut and socket size

Gary,

The 33 mm socket I just bought is 1.308” between flats. It fits the 1.280” nut from Long Island Corvette much better than a 1-5/16” socket, which as you measured is 1.350”, not the nominal 1.3125” value. For the 1.305” nuts you buy, the 33 mm socket might be too tight of a fit.

Gary

Gary------


I have had this problem with the fitment of the 1-5/16" socket on the pitman arm retaining nut. I consider the fitment of the nut in the socket to be "sloppy". However, a 1-5/16" socket will work but I use only a 6 point socket, never a 12 point. The industry standard across-the-flats size for a 7/8-14 nut (which is what the pitman nut is) is 1-5/16".

Unknown to many, there were actually 2 different nuts used. 1963-74 used nut GM #258779 which is an ancient part number. 1975-82 used nut GM #5667628. The former was discontinued in April, 1975 and replaced by the latter for SERVICE of all 1963-74 Corvettes. I actually have examples of both nuts and they appear to be identical in every way. Measured with my digital caliper I find both to be 1.285" across-the-flats. This is actually equivalent to 1-9/32". Once-upon-a-time I looked for a socket of that size and never found one.

A 1-5/16" 6 point socket is 1.3275" across-the-flats. With the pitman nut at 1.285", I think this explains the sloppy fit. But, it will work. The 33mm socket might be a better solution.

[David B.]

Re: Pitman arm nut and socket size

Part #s really help: 258779 & 5667628 are Saginaw Steering Gear Division numbers used by all GM Divisions. Listed in GRP. 6.861