I just got myself a 90' 4 runner 4x4 with the ADD system. When I shift into 4HI the ADD system will engage but the cars feels like its really bogging as soon as I left off the gas or clutch in, so much it will come to a complete stop somewhat abruptly. Also, if I go back into 2HI the ADD remains engaged and still bogs, until I come to a stop and reverse about 1ft, then the 4wd light will go off and I can drive in 2wd mode without bogging.

This is my first truck nevermind yota truck, is this normal? I thought the ADD should disengage when I go back to 2HI again, not only when I go in reverse reminiscent of pre89 auto hub days.

 

I have a 90' 4 runner 4x4 v-6. I am not wanting to sound stupid but what is a ADD system?

 

Probably automatic disconnect driveshaft, something like that. Some 4WDsystems have permanently engaged hubs and the front driveshaft (or halfshafts) disengage(s).

 

Check the alignment of your transfer case and check the oilin the case and the front diff. It sounds like you're bogging down from the 4WD catching and getting stuck from poor lube.