RRSG - Reverse Rotation Steering Gear was used on 1972 - 1978 Dodge W series trucks, if I am not mistaken.
The RRSG setup changes how the force from steering is applied to the frame. See pic below.
Several 1st gen owners on another Dodge Cummings forum have done the RRSG upgrade with positive results.
Swapping from the cross-over type steering box to the push/pull type is not a great upgrade. It's not that it won't work as you expect, but, if you have any future plans for lifting the truck, the push/pull steering box will result in significant bump steer. The achilles heel of this arrangement is the very short drag link. Should you want to add lift, the link becomes angled, thus further shortening the distance between the axle and steering box. This makes the tires naturally steer to the left, and limits steering to the right. When you hit a bump in the road, the suspension flexes and changes the angle of the drag link, resulting in an instant change in distance between the axle and steering box. This causes the steering to rapidly turn as you hit the bump. Without a suspension lift, the system works fine because the drag link is parallel to the road surface and any bumps you hit will not cause the drag link angle to change much, but if you lift the truck, the angle of the drag link already present, will magnify the bump/steer effect. There are push/pull drag links for lifted trucks which are adjustable and have an "S" bend in them to reduce drag link end bind, but since both ends are not parallel to the road surface, bump stop will still be an issue. The current side to side or cross over set up is the better overall system. The drag link on these is much longer which means they have reduced angularity when the suspension is lifted and that will result in far less bump/steer.
OTOH, if you're willing to make modifications, you can vastly improve the push/pull box by mounting it further forward on the frame, so that the pitman arm is at the same plane as the spring hanger (Most big rigs are set up this way) This will allow the drag link to swing in the same arc as the forward half of the leaf spring. This helps to neutralize bump steer.
Ed
I'm adding a correction and re-suggesting my comment with more explanation…. My correction deals with my comment over the cross-over steering part. Dodge didn't use cross-over style steering (A drag link which connects from the pitman arm, crosses over to the passenger side and connects to a steering arm on the pass. side of the axle) They were using a push/pull arrangement. They used two different steering boxes. They work the same basic way, but differ in where the sector shaft exits the box. Both use a push/pull type drag link.
I'm assuming you ran across an article which suggests using the older style steering box which has the sector shaft exiting the box from the side and not from underneath. I'm guessing that the author of the article is suggesting the older style box because of the way the force is applied to the frame. Heres my take. When you steer, the steering box creates significant "torque"to turn the pitman arm, which steers the tires. The force created by the newer box design (Sector shaft exits the box from underneath) tends to be directed in a side to side "push" This force can sometimes be significant enough to cause the box to try to separate from the frame or cause the frame to crack, or pop rivets within the vicinity of the steering box. The older style with it's side mounted sector shaft doesn't apply a side to side force, it creates a vertical rotational force which is better absorbed by the frame. (the force applied follows the direction of the frame rail) In theory, the older style would be better due to how it applies steering force to the frame.
The problem is, both types of steering boxes use an inferior push/pull style drag link. If you lift a truck with a push/pull style drag link, the angle created will produce bump steer because the short drag link cannot accommodate differences in distance between the pitman arm and steering arm on the axle, as the suspension flexes. The best solution is to convert the steering to use a cross-over style drag link, which is much longer and less prone to bump steer. The old style box cannot be converted. The new style box can be used, due to the location of the sector shaft being under the box. From there, a new longer drag link can be mounted to the pitman arm, cross-over to the other side and mounted to a steering arm, located on the opposite side. This is a far superior system and will accommodate more lift with less tendency to cause bump steer. The force applied to the frame can be reduced by spreading the load, via reenforcement to the frame rail. The old style box can be improved by relocating the box forward on the frame rail so that the drag link is the same length as the forward part of the leaf spring (From hanger to axle mount) This will help to reduce bump steer (So long as both are parallel to each other), but it doesn't solve binding at the drag link ends when the suspension is at max flex.
Ed
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