LJ72 4WD setup (need help fixing)

[kylepacemt]

Hi, i'm relatively new to the Landcruiser market as I bought my 1990 LJ72 (Square headlight) back in March and i've been doing some TLC to get it back to its former glory.

I need some help in understanding the proper way the 4WD (2wd > 4wd) mechanism works so I can troubleshoot my issue.

Basically my 4H button (temp 4wd) does nothing, no 4wd light comes on the dash when its pressed on. My low range selector works fine but its still in 2wd, and I also tried locking my mechanical front wheel hubs but still nothing.

Tried troubleshooting a bit but need a better understanding of the 4wd system.

Up until now i know there is an actuator in the transfer case that should have vacuum piping running up to the vacuum solenoids.

Are there any relays that control this mechanism and the vacuum is generated via the alternator vacuum pump ?

I am asking so I can diagnose the issue and hopefully solve it. Thanks in advance for any help

 

[Shayne]

Quick answer because I don't know the 70 series very well but i would imagine its permanent 4wd though i believe some have a 2wd option at the hubs on the front wheel ?

H= high ratio gearbox for on road driving ,

L = low ratio gearbox for off road driving

 

[kylepacemt]

Quick answer because I don't know the 70 series very well but i would imagine its permanent 4wd though i believe some have a 2wd option at the hubs on the front wheel ?

H= high ratio gearbox for on road driving ,

L = low ratio gearbox for off road driving

Hi, Thanks for your reply

to my knowledge its permanent 2WD and 4WD is temporary. In fact high/low gear shifter has written 2H>4L. The problem is i can't seem to get the 4WD light to go on in the dash and locking the front hubs and shifting the lever to 4L only gives me low gear on the rear axle so still in 2WD.

 

[Jasper Kotze]

Hello,

What I would suggest i mabe put the vehicle on 4 jack stands and test, because it could be the hub locks as well(unless you have the manual hub locks).

H4 button locks the front drive shaft to transfer case gearing. HI-R/Low-R gear lever select HI-R/Low-R respectively.

Seem like there is a relay like you said. Hope this helps.

See wiring diagram below :

 

[kylepacemt]

Hi Jasper Kotze

Thanks for your reply. The wiring diagram is very helpful thanks !!!

Regards my drive train, I have manual front locking hubs, but I need to get the electrical part sorted as the wires from the transfercase > vacuum solenoid > 4wd indicator relay > 4h switch are messed up as unfortunately the previous owner didn't have a clue regards electrics so most of my wiring was busted so I am getting that sorted atm.

Thanks a lot I will check again once my LC is back from the shop as I took it for an injection pump rebuild as it was leaking heavily.

Regards,
Kyle