Pitman arm compatibility

[billbob1936]

Hello. I'm searching for a fast ratio pitman arm/idler for my '73 Challenger but finding compatiblity conflicts during my search. I seeing listings for the arm up to the year of 1972. Did something change with the arms starting in 1973? Here's a photo of my setup.

 

[Vaanth]

Hello. I'm searching for a fast ratio pitman arm/idler for my '73 Challenger but finding compatiblity conflicts during my search. I seeing listings for the arm up to the year of 1972. Did something change with the arms starting in 1973? Here's a photo of my setup.

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Two output shaft, or sector shaft, sizes were used in 1962 - 1989 rear wheel drive car power steering gears (through 1993 in vans). A 1973 Challenger with power steering was originally equipped with a large sector shaft power steering gear, with matching large sector pitman arm.

The different shaft sizes and applications are as follows:

Large Sector:
All 1973 and later A, B, C, D, E, F, J, M-bodies, all E-bodies with the "TA" box, all C-bodies and D-bodies (Imperial), and all 1971-1993 B-series vans were originally equipped with the large sector shaft power steering gear. The large sector shaft roughly measures 1-1/4" near the top of the splines on the shaft. The original nut that retains the pitman arm on the shaft has a hex size of 1-5/16".

Small Sector:
All 1962 - 1972 B-bodies, 1960 - 1972 A-bodies, and 1970 - 1972 E-bodies (except cars equipped with the "TA" box) were originally equipped with the small sector shaft power steering gear. The small sector shaft roughly measures 1-1/8" near the top of the splines on the shaft. The original nut that retains the pitman arm on the shaft has a hex size of 1-1/8".

For some more information and comparison of pitman arms, refer to the following:

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The following image shows a small sector shaft pitman arm for pre-1973 vehicles (top) and 1973-later vehicles (bottom):

Measuring the actual spline diameter is a little ambiguous, but the following images show measuring, roughly, the diameter of the opening at the top inner edge of the splines. Note that the measurement is a little smaller than the outer edge of the splines and less than the measurement of the sector shaft splines slightly above where the pitman arm sits. The steering sector shaft is tapered for a wedged fit to the pitman arm itself.

The following image shows a small sector shaft Moog K-780 pitman arm for pre-1973 E-bodies and B-bodies measured:

The following image shows a Moog K-7076 pitman arm for 1973 -1974 E-bodies, 1973-later B-bodies, and more measured:

C-body pitman arms are all large sector. The arms are longer than those on the smaller cars. The longer C-body pitman arm also has different positioning, or "clocking" of the master spines, so it cannot be directly used on a E-body, etc. The following image shows a C-body pitman arm measured:

The following image shows a C-body pitman arm and early B/E-body pitman arm compared:

The original T/A fast ratio pitman arm is longer than the "standard" pitman arm and fits a large sector shaft. The following image shows a T/A fast ratio arm on a T/A steering gear:

The T/A fast ratio arm is marked as shown in the following image:

The aftermarket fast ratio pitman arm from Proforged, part number 103-10031, fits a small sector shaft. A Proforged 103-10031 is shown in the following images:

Firm Feel lists both small sector and large sector fast ratio pitman arms:

• Small: PAFRS0
• Large: PAFRL0

Link: Firm Feel Fast Ratio Pitman Arms

The following image shows a Firm Feel pitman arm:

 

[billbob1936]

Great write up Vaanth! Other than Firm Feel, I have not been successful finding a large sector unit (and matching idler arm) for my 73 Challenger. Bergman auto is currently working to see if they can find the right parts.

 

[Challenger RTA]

Are you aware that you have to change the idler arm to keep the steering geometry correct. C body idler arm K7014 . Just want to say it to be sure.

The original TA box was just a C body box that was modified and cast with the TA designation. It has a larger sector gear than other 70 B and E cars. They also modified the box with internal stops so it stops before it can contact the frame. So the sector for a TA is not just a C body sector.

 

[Challenger RTA]

'73 Challenger Resto-Mod - Steering Geometry correction effort

This is another "retro post". This was work I had done prior to putting on the wider tires. The problem was that I had my power steering box rebuilt by Steer and Gear, to the TA specifications. I purchased the longer pitman arm and the longer idler arm which was not part of the original TA...

• Buckminster
• Jul 5, 2024

 

[billbob1936]

Are you aware that you have to change the idler arm to keep the steering geometry correct. C body idler arm K7014 . Just want to say it to be sure.

The original TA box was just a C body box that was modified and cast with the TA designation. It has a larger sector gear than other 70 B and E cars. They also modified the box with internal stops so it stops before it can contact the frame. So the sector for a TA is not just a C body sector.

Ok, so after reading that, would it be a more simple plan to just go with a fast ratio steer box with internal stops, and just forget about changing the pitman and idler arms?