I have a Montero '94 with 3.0 auto. Lately I noticed that transmission doesn't go into overdrive. The switch on shifter seems to work, because the OD light goes on and off if I play with switch, but no change in gear on highway speed. Does anyone know what could be the problem and is there any easy fix or something to try? Transmission oil looks clean, and doesn't smell burnt. All other gears shift good and don't slip.

Raider 6.0 V8 386hp, 397ft lb, 3?exhaust, Megasquirt ECU, EDIS ignition, Innovate LC-1 WB Lambda, NV4500, NP241 with JB conversions ?super short? SYE kit