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I have a friend that wants me to replace the steering gear box on his 74 Delta 88 w/455. Rockauto shows the non-A/C gear box is the same as 72 Cutlass but if it has A/C it calls for a different part number. Can anyone please share what the differences are between A/C and non-A/C gear boxes?
The parts book confirms that they are different. 455 cars without A/C use PS box assembly P/N 7818145. With A/C use 7825371. The '371 box was also used in Ninety Eights and Custom Cruisers. I suspect the difference is in the diameter of the torsion bar that operates the servo valve that directs the pressurized fluid in the box. A smaller torsion bar twists more easily when you turn the wheel, which reduces force required at the wheel. I'm guessing the smaller bar was used in the heavier cars (Ninety Eights, wagons, and D88s with the added weight of the A/C system). Here's more info on the torsion bar.
Here's an example of the differences in that torsion bar in Saginaw boxes.
I should've just sent you a message as I figured you would be the one to respond!!
Thanks for the elaborate response, makes perfect sense if the torsion bars are different diameters.
Originally Posted by joe_padavano
The parts book confirms that they are different. 455 cars without A/C use PS box assembly P/N 7818145. With A/C use 7825371. The '371 box was also used in Ninety Eights and Custom Cruisers. I suspect the difference is in the diameter of the torsion bar that operates the servo valve that directs the pressurized fluid in the box. A smaller torsion bar twists more easily when you turn the wheel, which reduces force required at the wheel. I'm guessing the smaller bar was used in the heavier cars (Ninety Eights, wagons, and D88s with the added weight of the A/C system). Here's more info on the torsion bar.
