put my ohmmeter on the solenoid resister measured between +B and other terminals. The reading was 3.8-3.9 ohms. Should I replace the solenoid resistor. According to my Toyota Repair Manual (for my '87 Runner) the readings should be between 2-3 ohms.

1987 Runner 22RE Auto Trans.

 

If your truck is still starting and running ok, I wouldn't worry about it. You are talking less than 1 ohm, the discrepency could be in your multimeter. Your 30-50 dollar multimeters or even a 100 dollar meter really doesn't have a lot of accuracy built in. Just as an indication of what industrial grade accurate multimeters cost... the least expensive models we use at work are Fluke 87's which are around $550.00 and the other models go up from there.