I was wondering if anyone could simplify the actual workings of my 4wd system in my 1989 Toyota pickup 3.0 5 speed.? I am familiar with it having auto lock hubs but are they electrically or vacuum operated.
New to the forum and to Toyota trucks.

 

Now Do you have hubs or just drive plates ??

Then Toyota did have automatic Hubs which were one of there engineering blunders .

If You indeed have the ADD system it is an electrical /Vacuum system Which was first introduced in 1989

They do have a tendency to quit working if left unused for long periods of time.

Doing a Search with your favorite search engine Toyota ADD should give quite a few articles to explain it.

 

Don't listen to him; he was upset when Toyota put in electric starters and took out the place to put the crank.

All Answers are found in The Good Book: http://personal.utulsa.edu/~nathan-b...26addcontr.pdf A switch on the transfer case actuates two VSVs (probably on the passenger-side apron) which switches vacuum between two lines down to the actuator on the ADD.

 

So many cranks and no engine to use them on!!

If you like Automatic Hubs more power to you !!`

 

Thanks for the info guys. After posting last night I went and took a closer look and found that it is an ADD system. Vacuum operated to engage front axles. And NO,I do not prefer auto lock hubs.I would rather have to dive in to 3' of mud and thorns to llck my hubs manually than to rely on auto locks.😁 But that shouldn't happen anyway, they should have been locked already!
Thanks for the info.