Hello and thank you for using just answer!
Is this an automatic or manual transmission truck?
Are you only trying to replace the transmission fluid or are you trying to service the 4x4 also?
It has a manual 5-speed transmission (R150F).
Need to just replace transmission fluid.
All other fluids have been replaced. All fittings have been greased. Manual hub bearings and seals replaced. Brake pads and shoes have been replaced. Brake lines have been flushed and new brake fluid added. Radiator has been replaced; new coolant added. New tires. New Shocks. Halogen headlight upgrade. New timing belt, pulleys, tensioner, water pump, oil pump. Replaced stock fan with electric.
Thank you for the reply and clarification.
This transmission takes standard gear oil.
If you look at the BOTTOM of the transmission case you should see a 22mm (7/8 inch) drain plug, this is the one you need to pull. Then there is another matching plug on the side of the transmission case to fill and flush this unit.
The 2 plugs you described earlier on the back are for the transfer case and are not linked with the transmission fluids.
Actually, the drain and fill plugs on this chain driven transfer case are on the back end. No problem with them.
Now, in the daylight, I see what I mistook in the near dark as an additional drain plug; definately not a drain plig.
However, for your information, the R150F transmission has a 15/16 drain hole near the bottom of the transmission that faces the passenger side (front drive shaft side) and is 13 1/2 inches back from the front of the bell housing.
The fill hole is 15/16 on the drivers side of transmission, about 1/4 to 1/3 up the side, and 13 1/2 inches ffrom the front of the bell housing.
I have used Redline MT90 (75W-90, GL-4) synthetic gear lube in several transmissions. Shift is smooth and runs quiet. Use Mobil 1 (75W-90, GL-5) in differentials for many years. Have had no problems; very minor oil seepage around gaskets, no seal leakage.
Thanks for your time!