jen88

Hey, i have a '92 pickup, manual transmission, have a problem with my ADD system. When i gear into 4wd, the drive shaft up to the front diff turns, but i get no power to the front wheels. also no indicator light on the dash. I understand that the ADD system in these trucks is often a problem, and theres many places it could go wrong.

I cant afford at the moment to put in auto hubs, which i have been reading is a good way to bypass the system all together. So im looking for a troubleshooting checklist of sorts, or the top problem areas that i could check to try to get the system operational again.

im new to toyotas, i really appreciate the help. thanks!

wyoming9

iTrader: (1)

If your not getting the light on the dash.

I would look at the power supply 10 amp gauge fuse

The ADD relay which is up under the dash to the left of the radio.

Then check that the switch works like it should .

Work through the electrical side making sure that all works.

Then on to the vacuum system.

The 2 VSV ( Vacuum switching valve) control the servo motor that engages and disengages the ADD differential .On the right inner fender.

If you were close I would be glad to help in person.

Toyota recommends to switch this system often to keep it from getting stuck which happens often it seems

The manual locking hubs may be the most cost effective repair .