2nd Gen Automatic Transmission Don't Shift Into Fourth Gear

Hi,
My '91 T4R doesn't shift into fourth gear. I have no codes on the OBD1 and O/D light turn on and off. Any ideas ?? Can it be a solenoid ?? Truck has 45K. Spent many years parked.
Any ideas will be greatly appreciated.
Thanks guys !!!

 

check your overdrive button. The light might be out and you might have the overdrive off engaged. Always start with the easy stuff first…

 

You could also do a few drain and fills on the tranny. Fluid is probably very old. Also your 4Runner will not shift to 4th while the tranny is cold. Make sure you have it warmed up properly. Mine takes about 3 to 4 miles before it shifts to 4th.

 

I would buy a new solenoids off eBay, drop the pan drain it change the filter put all new solenoids in..