Re: '55 Ultramatic won't go into reverse

Posted by HH56 On 2017/3/20 14:21:24

All the valves and the three separate sections of valve bodies containing them are shown in the Twin Ultramatic section of 55-6 service manual but here is a photo of the 55 valve body containing the reverse shuttle valve.

The struts are located directly above the two piston (or brake) assemblies which are connected to the valve bodies. In addition to what is mentioned in the manual re proper positioning of the strut (means make sure the little inch long piece of metal connecting the band to the actuator is actually in position so the piston can bring in the band) there is a pin which forms the pivot for the actuator. That pin has a groove in the middle which has proven to be a weak point and many of the 55-6 pins have broken. If a pin breaks it can come out and actuator no longer has a way to transmit piston force. Also make sure the band adjustment is good. If the band has worn excessively for whatever reason, the piston cannot clamp it tightly enough around the reverse drum to stop drum from rotating..

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