'70 Z-28 Manual Steering

70moneypit

Veteran Member
Jul 18, 2012
169
North Texas
FlaJunkie said:
Anyone else with early 70 Z28's have the 3864881A pitman arm? PS/non-PS?
Very confusing into. That pitman arm is correct for any power steering optioned 1970 Camaro, according to the catalogs. It does not appear to be correct for a manual steering car, but maybe in the early part of the year they did not have all three different types?

The early suffix coded "A" version of 3864881 must have been superceded by revision "B" by at least May. Of course, there could have been an overlap in usage of the older "A" and the newer "B", as it could have theoretically taken them a few weeks to use up all the "A"s in the bottom of a bin if "B"s were piled on top of them before the bin was completely empty.

The fact that the actual basic numerical part number did not change (on either the part or in parts catalogs) would indicate it was a minor revision of the same design and the two versions are/were totally interchangeable.
 
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DCL70

Veteran Member
May 5, 2007
2,063
The South of N.H.
FlaJunkie said:
I am an 02C manual steering and I have never changed the pitman arm. Mine is an 3964881A. Wonder what the letter difference is?
Also wonder what the GMT 1 means? General Motors Tonawanda Plant #1?

My 1938-1971 Chevrolet Price Schedule (March 1971) has a list of abbreviations on the 2nd page.

GMT - Parts or Accessories stocked at General Motors Truck Division Warehouses.

Did GM have their own foundry that made suspension parts for trucks and cars?
Just an idea......

Dave
 

FlaJunkie

Veteran Member
Lifetime Gold Member
Mar 24, 2001
6,459
Rockledge, Florida
DCL70 said:
GMT - Parts or Accessories stocked at General Motors Truck Division Warehouses.

Did GM have their own foundry that made suspension parts for trucks and cars?
I have read that they did have a truck parts foundry...I just never knew much more about it.

So, looks like they made this pitman arm at a GM plant.

I would still like to ask any other 70 Z28 owners with manual steering what their pitman arm part number is.

I wonder what the specs are on the 3964877? A pic of one would be nice!
 

DCL70

Veteran Member
May 5, 2007
2,063
The South of N.H.
Has anyone ever seen a Pitman arm with a "3964877" casting (or forging) number?
The GM part number is generally not the same as the casting number but is some cases it is.

Isn't it possible that the GM # 3964881 and GM # 3964877 Pitman arms are made from the same casting (or forging) with "3964881" as the casting (or forging) number?

Is the hole size in the Pitman arm the same size for both the manual steering box and the power steering box?

Is the hole size in the Pitman arm the same size for the different centerlinks?

My 1990 TRW Chassis parts catalog (for 1979 & prior models) does not even list a Pitman arm for the 1970-1979 Camaro models as it is a "Non wear" item.

The TRW #DS829 centerlink is listed for 1970-1971 Camaro models w/SHP 350 & P.S. and all 1974-1979 models. The TRW #DS830 centerlink is listed for 1970-1973 Camaro models w/P.S. (exc. SHP 350 and 1973 models w/AC.).

My 1970 Chevrolet Parts Catalog (Oct. 1970) lists the following part numbers for the centerlink (aka "Relay Rod" in Gr. 6.870):
3964873 - 1970 Camaro w/SHP 350 & 70 Camaro w/P.S.
3964883 - 1970 Camaro (exc. P.S., SHP 350)

My educated guess is the difference is just the centerlink (aka Relay Rod) length.

Dave
 
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Gary S

Administrator
Lifetime Gold Member
Apr 14, 1999
24,524
Bismarck, North Dakota
70moneypit said:
The early suffix coded "A" version of 3864881 must have been superceded by revision "B" by at least May. Of course, there could have been an overlap in usage of the older "A" and the newer "B", as it could have theoretically taken them a few weeks to use up all the "A"s in the bottom of a bin if "B"s were piled on top of them before the bin was completely empty.
.

My 4/70 car has an "E" version of the 3864881.
 

Mulsanne Blue

Veteran Member
Mar 31, 2009
234
Goshen, Indiana
Top is the 3964883 for manual steering and the bottom is the 3964873 for power steering. Note the off-set difference at the pitman hookup. All manual steering use the 3964883 center link. The different off-sets evidently require different length pitman arms. So, here's my hypothesis: All p/s use the 3964881 arm, the manual uses the 3964851 arm with the 7809668 (cast no.) steering box, and the 3964877 with the 5679142 (cast no.) box. The 3964851/7809668 is used on manual non-HP cars, and the 3964877/5679142 is used on the manual Z-28's.

The only manual steering untouched Z that I know of is clill's 1,100 mile car. Charlie, could you check to see which pitman arm is on yours? Should clear up some things :) .
[URL=http://s716.photobucket.com/user/kmas5/media/CenterLink_zps277ebbf0.jpg.html] [/URL]
 

70lt1z28

Veteran Member
Gold Member
Oct 3, 1999
4,837
Beavercreek, Ohio, USA
What I've always suspected and seems to be confirmed by the Camaro Supplement to the Chassis and Overhaul Manual page 13 is that the Z28 had the same manual steering box as the 6 cylinder and only increased the steering ratio by using the long 3964881 pitman arm. This then necessitated the use of the power steering center link and its corresponding idler arm. This only applies to the Z28. So, to change from power steering to manual only requires locating a 6 cylinder power steering box and some workout time at the gym to beef up those arms.

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