Re: '55 Ultramatic won't go into reverse

Posted by HH56 On 2016/10/14 21:08:42

There are no cables used on Ultramatics.

One question would be if there is any slop in the shift lever. Reverse is the last position the manual selector valve can travel to and your idea of not traveling far enough may be valid. There are some wear spots but one place to check is the bellcrank assy. That is mounted between the frame and engine. It transfers the vertical rod motion from the gearshift lever to horizontal movement going to the trans lever. It has some rubber bushings and also a mount on the engine side which can loosen. Make sure there is no lost motion there.

One issue with Twin Ultras is an internal setscrew which can strip out of a potmetal lever. If it has loosened, the lever which moves the valve may not be able to pull it to the required position. There is a stop the setscrew also holds and that could be out of position blocking full travel. I would check that loose screw possibility by removing the long rod from the lever on the drivers side of transmission. Grasp the lever and move it thru the positions.

Park and Neutral share a position on the valve. Assuming the gearshift lever was in park when you started, the valve should be in the neutral detent when you start. Moving the lever out of park to neutral is a fairly long throw and then it will be very short movements between the other selections. A strong detent should be felt at each stop. Including neutral, there are 5 in total. The final one is reverse and should feel like the others. There should be a minimal amount of slop in the action. After you go thru and check the number of detents, move the lever in the opposite direction to about the middle and check the amount of movement. There should be almost no motion at the end of the lever when it is in a detent. If the end of the lever moves more than a tiny bit as you try to move the lever back and forth the setscrew may be loose.

Another issue is a pin which holds the piston to band levers so they pivot to tighten the bands can break. If that has happened the reverse piston may be operating but without the full lever action, it may not be able to tighten the band enough to keep the planetary ring from rotating.

If everything in the linkage checks good, it is possible one of the valves has stuck. In addition to the manual valve there is a small auxiliary valve which has to move so fluid can bleed out of the other side of reverse piston. After years of sitting it is possible that valve cannot move to allow fluid out and the piston cannot move.