QUESTION: 4wd broken; I hear no "click" under dash. Does this mean I should check the relay first? Where is the ADD relay for my 1996? I looked for it for like an hour last night. I found "markers" and "starter" and "fuel pump" but no ADD.

BACKSTORY: Well, I'm new to the site but not to my T100. I've had my maroon 1996 T100 SR5 4WD since 2001. It's been my daily driver off and on for 12 years...got 223k and running strong.

That said, my 4wd stopped working a couple years ago. I don't need it much, so I never devoted much time to working on it.

And, yes, I've done my research. I've read probably 20 different articles about the ADD system and the actuator and vacuum routing and switching to manual hubs (which I may do in the near future).

However, today we have 7" of snow here in Maryville, just southeast of Knoxville, TN, and I would like to see 4wd today to go have some low-impact fun!

I spent a couple hours working on it last night, plugging and unplugging vacuum lines. I could NOT find the relay under the dash. Is it further up, actually under the instruments, rather than down in the footwell? So I have to take the dash more apart than I already did? I removed the lower panel already with the clutch overridge switch and all that (and could not get the hood latch cable disengaged).

I am going to check the lines at the actual actuator in just a bit, and probably pull the actuator just to see what's up (maybe it's just stuck), but my main question after all this is:

Should I hear the "click" under the dash before anything else happens? In other words, does "no click" mean "bad relay"?

THANKS EVERYONE!

-Lee in Tennessee

 

Update: I pulled the actuator. The gear oil in the differential was nasty, so I'm changing that. I am replacing the vacuum lines coming down from the vacuum switch valves. Nothing is obviously wrong, but I am hoping that just having everything apart and replacing some probably culprits may make things magically start to happen again.

One note: The sleeve that is moved by the actuator inside the differential doesn't seem to move much, perhaps 3/4" left and right? I guess it moves the same distance as the fork in the actuator, but it seems like less. It would not move far toward the passenger side to expose the gear. We'll see....

 

UPDATE: I read this excellent article on the ADD system.
http://www.off-road.com/trucks-4x4/t...tem-19259.html

I changed the front differential fluid, changed some vacuum lines from the VSVs (still not sure if those work).

Then I ran a vacuum hose directly to the actuator and it works...it locks the front drive shaft to the front differential. However, still no 4wd! No light, no relay "click" in the cab, and no 4wd.

Does this mean that the transfer case is not transferring the power to the front drive shaft?

 

Without a manual in front of me I can't be certain, but I think the light / click circuit is sent from the ADD. I pulled my ADD and had to jumper the wires at the connector on the driver side of the engine for my light to still come on.

If you are worried about it actually being in 4wd, pull the T-case lever back into 4wd and try turning the front drive shaft.