Hi all.

Have a 1996 JDM Surf. Recently the 4WD stopped working. Indicator lights keep flashing. Truck will not shift into 4x4 despite several attempts, (shifting from reverse / neutral / drive etc.). 4LO gearing there.
Internet said the ADD solenoid is a common issue. Replaced it with not change. Vacuum lines are in good shape and tested out as well sealed.

Any thoughts?

Thinking about abandoning the ADD option and going with manual hubs. What would be the byproduct of this? I gather the main vacuum line that activates the ADD should be disconnected and the worst case is the shift on the fly 4X4 button will no longer work.

Anything else I should consider?

 

Is the ADD actually engaging? Jack up one front wheel, put it in 4WD, and see if the wheel turns or not.

If it is engaging, then it might just be the switch on the front diff not indicating that it is engaged.

If it isn't, and you're sure the solenoid is sending the right vac down the right lines, then there might be something wrong with the actuator.

 

No - For sure not going into 4x4. The actuator I installed was used - perhaps 2 in a row not doing their thing.

 

There's a thread in this forum about the 4WD on 1999-2000 4Runner Limited not working properly. Most of the 1996 N185W Hilux Surfs have the Multi-Mode 4WD system which is the same with the Multi-Mode 4WD used on the 1999-2000 4Runner Limited. Perhaps the solution to your problem is in that thread.

EDIT:
https://www.yotatech.com/forums/f2/4...er-ltd-131201/
https://www.yotatech.com/forums/f2/a...thread-284592/

 

I would start with the position switches. There is one on the front diff, and then a few on transfer case as well. Test them with a multimeter to make sure they have good conductivity their the entire range of pushing the plunger… not just top and bottom.

if they all check out okay, next check that vacuum applied to either side of the diff switch ACTUALLY moves the shift fork.

if that checks out okay, take the round cover with the three bolts off the transfer case actuator and check if the contacts are all clean. (You can check my build thread I have some pics)

 

Good stuff.

Vacuum lines are nice a sealed. I did notice the one end of the front diff ADD seems to be bypassing when vacuum is applied. I can hear it in the actuator, no clicking or any indication its trying to switching to 4x4. Switching the vacuum lines makes no difference. I would gather the ADD should be sealed on both ends??? I am leaning towards this used unit being duff.

I removed the 2 x plunger relays and there is no moisture and they move freely. I did not test for continuity - will do this later.

I noticed another vacuum operated pot on the transfer case - What doe this do??

The help is appreciated. My first Toyota so I am learning all the in's and outs'.

 

Back on the front diff, use a mighty-vac (or even just sucking on the hose by mouth) and see if applying vacuum to each side of the actuator makes it manually move. The ADD mechanisms may be gummed up and not shifting if they haven’t been exercised in a long time.

 

Morning.

For this ADD - when I apply vacuum to one side of the ADD it stays sealed. When I apply vacuum to the other side I can clear hear the vacuum bypassing in the ADD pot. I assume this should not happen.

My issue is Ive been told this part new is 6-8 week lead time and $700 from my local small town parts shop. The ADD that is currently installed is from the local wrecking yard. It seems I have two bad ones in a row.

 

are all your tires the same size? i read of a guy having trouble with his 4WD system and had replaced several parts and didn't solve the problem. later on it was found out that he has 32" tires up front and 31" tires in the back.