Offroad-Express

I just bought a LJ78 Prado and when I got home I decided to have a play with the 4wd. But no joy, front wheels won't engage with the H4 button or L4 lever. The hubs have been changed for manual ones and seem to be working. I locked the hubs and jacked each front wheel up individually and when I turned each wheel the front driveshaft turns. So I believe the transfer case isn't engaging. Any ideas? Or common problems with these?

from memory, there are two solenoids that control it, in the engine bay, drivers side on the firewall, two little black cylinders,


(picture is just a random one so dont worry about arrows)

one will be going off to the transfer case and one to what was your electric hubs. it would be worthwhile testing those by directly plugging the inlet to outlet, that would tell you if it was something in the transfer case or the electrics & solenoids

^^^^^ Yep sort of but electric hubs work on electricity not vacuum, the 2 solenoid's on the firewall switch the transfer case between 2wd and 4wd, one pulls the diaphragm actuator across to 4wd and the other pulls it back to 2wd, its not uncommon for one of them to fail (usually the 4wd one ) you can swap the 2 outlet side hoses over and see if 2wd mode puts it into 4wd, its also worth checking the vacuum hoses are all intact (not perished or damaged ) and have vacuum right down to the diaphragm actuator on the transfer case, the rubber diaphragm in the actuator can also suffer from old age and perish or split, the solenoid's are often colour coded brown=2wd and blue=4wd

Got it working !!! The previous owner had removed the A/C pump and left the vacuum line unplugged when they finished. All I had to do was remove the "T" so now it just takes it's vacuum from the alternator.
Another helpful thing I learnt in another thread was, even though I have manual hubs, I should still press the hub lock button when I engage them because then the 4wd light will work and also I won't forget they're locked.

the electric hubs will fail at some point 3 options oldblue's hub mod , adaptors and manual hubs, and hilux stub axels mod

I've already got manual hubs on this one, but thanks for the tip