us gear dual range

[ajg6989]

My 86 suburban with 6.5L diesel has a US Gear dual range and its stuck in low. I was driving home the other day at 60mph and it went from high to both lights then to low and has since stayed in low. When it jumped into low I lost my rpm gauge until today when it started working again. I checked the fluid level on the side of the unit and its good. I also checked the fuse that comes off the switch under the dash and it was good. I can get up to 65mph but the gauge is showing 3200rpms. I tried going up to 30mph hitting the button and letting off the accelerater but its still in low. Any Ideas was thinking maybe the relay?

[carco]

Been a long time, they used to be built by Doug Nash. I would chk the wiring be sure B+ and grounds are good to the points intended. If the wires shorted somewhere it may have shifted its self and is now locked due to lack of proper circuitry. Chk the 2 speed shift motor, that it does work, the older units had a shift motor the same as medium duty trucks in the 90's. just a few thoughts,, HTH......................