4WD not working....still

Hey whats up, so 4wd and rear elocker have not been engaging, after buying the truck last February my 4wd would work and it gradually started to decline since, and now is toast. After reluctantly bringing my tacoma over to a toyota dealer, they tell me my transfer case ADD is not working properly, quoted $1,760! No way I'm paying that. They also tell me my front differential ADD is not working properly, adding another $455...They also stated that the actuator switch* in the transfer case may be the ONLY problem, and once replaced, could fix everything, so I'm at a loss for what to do honestly. Hoping for some advice from you guys, thanks. -Will

 

Start with a repair manual and do your own diagnostics . Checking for proper voltages at the transfer case would be a good place to start .Do you have a digital volt / Ohm meter ? Do you have a service manual ?