I've Googled, checked forum boards and haven't been able to find my issue. Truck is an 87 4Runner and transmission has at most maybe 3k on it since rebuild, but it was also 6-8 years ago. Truck was hardly driven as I was working on rebuilding other parts of the truck plus life got in the way. So, you can feel the transmission shift but it's like it doesn't actually shift. Starts off taking 1st a split second to engage then shifts to 2nd almost immediately then to 3rd then OD but rpms never really drop. Ran through gears manually and once I hit 3rd pressed the OD button just to force the shifts. End turning 3k rpm at 30 mph in OD. There's no CEL flashing or OD light either throwing codes, fluid's clean and doesn't smell burnt. Anyone have a direction they may point me for troubleshooting and testing? Problem with transmissions like this is determining if it's a mechanical or electrical issue. Need to add I've been driving the truck recently with no signs of issues. Parked one day and the problem happened as soon as I drove it the next day.