WTB TA steering box
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340challconvert
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I believe the internal difference were the “stops” to prevent the wheel from turning extreme left and extreme right so the 15” wheels/tires would not hit the frame rails due to the longer pitman arm.
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340challconvert
Well-Known Member
Brian, you are correct in that there was only one pitman arm diameter size on Mopar boxes until 1973 (the smaller 1 1/8 vs the larger 1 1/4)
Information on an article I read:
It seems there wasn't ever a fast ratio power box with a different worm pitch. The "fast ratio" power boxes were just like a regular box internally except they had a shorter travel built into the box and a longer pitman arm.
Fitted to the T/A and AAR (they were actually an option and also fitted to some JS and BS cars in 1971).
An original "fast ratio" box is either from 1970 or 1971 and therefore it will have the same sector shaft as those years (the smaller one).
What created the reduced turning ratio was the longer pitman arm. It changed the number of lock to lock turns from 3.5 to I think is 2.7.
Information on an article I read:
It seems there wasn't ever a fast ratio power box with a different worm pitch. The "fast ratio" power boxes were just like a regular box internally except they had a shorter travel built into the box and a longer pitman arm.
Fitted to the T/A and AAR (they were actually an option and also fitted to some JS and BS cars in 1971).
An original "fast ratio" box is either from 1970 or 1971 and therefore it will have the same sector shaft as those years (the smaller one).
What created the reduced turning ratio was the longer pitman arm. It changed the number of lock to lock turns from 3.5 to I think is 2.7.
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Mopar Mitch
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The pics above are what is the T/A factory setup. The casting on the box calls out TA (I'm not sure about the numbers vs a standard PS box). The FAST RATIO pitman arm is required to make it the "fast ratio"....12.7:1, 2.7 turns lock-to-lock). Realistically, you could install a longer aftermarket "fast ratio" pitman arm and get the same results. Yes, the tires will rub the frame rails... (pending the size of your tires) regardless of your setup.
Now, if you don't know this already, the factory never properly installed the longer required Idler Arm... to match the correct turning radius of the longer "Fast Ratio" pitman arm. The factory result is that the Driver side front wheel turns quicker than the passenger side wheel, and the radius is different per left turn vs right turn. All that is needed to correct this factory oversight is to install the longer idler arm from a ~70 C-body (Fury, etc). In other words, there was never such a thing as "fast ratio idler arm"... anyone (Firm Feel, Hotchkis, PST, etc) who refers to having "developed" or created such a thing is just plain wrong... jumped onto the band-wagon of calling it such a thing... its simply a C-Body ~70 idler arm... always has been... always will be... go order it from Moog or other.
Avoid the Federal-style power steering pump (as was factory for T/A setup, or, to the best of my knowledge, most all of the Mopar HP engines which also had a 3.55 or numerically higher rear gear ratio). The Federal PS pumps cannot, keep up with rapid L-R-L-R motion assist, even much worse as RPMs would be on the higher end, such as 3-4-5000rpms... performing a pylon slalom manuever. ONLY use the SAGINAW style PS pump.. a superior unit found in the common 3.23, 2.94, 2.76 rear end ratio Mopars. There are some newer light-weight style PS pumps recently on the market, but I don't know about their reputation, especially for quick L-R-L-R autocross manuevers (again, typically at higher RPMs).
If you further want to enhance the steering response, regardless of which PS box, consider a smaller diameter steering wheel.. quicker reaction time.. less actual time top physically turn the wheel. I've tried progressively smaller wheels... the Mopar factory TUFF wheel is smaller, but slippery... there are some aftermarket brands that have a better grip. I've ultimately settled on an 11.5" diameter (~5" deep) "Superior" brand wheel.. thick rubber grip... amazing results!
Now, if you don't know this already, the factory never properly installed the longer required Idler Arm... to match the correct turning radius of the longer "Fast Ratio" pitman arm. The factory result is that the Driver side front wheel turns quicker than the passenger side wheel, and the radius is different per left turn vs right turn. All that is needed to correct this factory oversight is to install the longer idler arm from a ~70 C-body (Fury, etc). In other words, there was never such a thing as "fast ratio idler arm"... anyone (Firm Feel, Hotchkis, PST, etc) who refers to having "developed" or created such a thing is just plain wrong... jumped onto the band-wagon of calling it such a thing... its simply a C-Body ~70 idler arm... always has been... always will be... go order it from Moog or other.
Avoid the Federal-style power steering pump (as was factory for T/A setup, or, to the best of my knowledge, most all of the Mopar HP engines which also had a 3.55 or numerically higher rear gear ratio). The Federal PS pumps cannot, keep up with rapid L-R-L-R motion assist, even much worse as RPMs would be on the higher end, such as 3-4-5000rpms... performing a pylon slalom manuever. ONLY use the SAGINAW style PS pump.. a superior unit found in the common 3.23, 2.94, 2.76 rear end ratio Mopars. There are some newer light-weight style PS pumps recently on the market, but I don't know about their reputation, especially for quick L-R-L-R autocross manuevers (again, typically at higher RPMs).
If you further want to enhance the steering response, regardless of which PS box, consider a smaller diameter steering wheel.. quicker reaction time.. less actual time top physically turn the wheel. I've tried progressively smaller wheels... the Mopar factory TUFF wheel is smaller, but slippery... there are some aftermarket brands that have a better grip. I've ultimately settled on an 11.5" diameter (~5" deep) "Superior" brand wheel.. thick rubber grip... amazing results!
rklein71
Well-Known Member
This is what I like about these posts, I am always learning something. Change of speed here. My 383-s was ordered with a fast ratio box which did have a different ratio built into the box. Rod
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