sorry-just noticed in an earlier post that you do have auto 4wd so my vacuum trick will not prove anything as the slip shaft is always engaged in any mode. Keep us posted as .....it sounds like you may have 4wd. Maybe too greasy to tell for sure. Maybe your tires are not the best...If you have a floor jack and a blacktop drive or a garage bay jack up the rear end from the pumpkin. Start it up, put it in 4wd, then drive and slowly release the brake. If the front wheels pull the vehicle(careful-slowly is all you need) then you have 4wd and you issues are with the items I previously stated. PS not sure about the RPM's as I never paid attention as long as it worked. I think, in conclusion, you have to determine if the 4wd is working as you may be ok. And I usually do the 4wd trick in 2wd as the vehicles I'm doing it on-the 4wd is not working. Not sure this is an issue with yours(being in 4wd) as it may already be working and this procedure not neccessary. JP

 

I'll give that a try when I get some time....maybe Sunday. I just don't get why I can get it in 4L but the light will never turn solid.

 

I put the truck up on a floor jack and neither 4H or 4L worked. I took the battery out just to make sure the actuator was still good. Everything down there looked brand new. The cable was pulling freely. What is the thing directly over the distributor on the fire wall? It has to do something with vac. I am again stuck, someone give me more ideas please.


Where is this switch that is on the transfer case? I have the NP8.

 

The vacuum switch on the transfer case is located around towards the top side of the transfer case on the driver side.

Check out THIS POST for a picture of the transfer case.

When you say that neither 4L or 4H worked, were you referring to neither worked at putting power to the front axle? Did the front driveshaft spin?

 

didn't the first post near the end say-auto 4wd? Wonder if there possibly is an issue at or near the vacuum celonoid above the cap, on the firewall? I've gotta run now but Kyle if your out there-maybe you can let him know(if that is indeed the style he has on his 01?) about this celonoid-the vac. need to it and thru it???JP PS good luck

 

Woops... Made a mistake without checking things. I am sorry, yes, NP8 is the active 4wd transfer case. I was thinking NP1 instead of NP8 even though I typed it out...

 

It didn't get any power to it. I couldn't tell if the front drive shaft spun or not as I was by myself and I really didn't want to get out to the truck with it in gear.

As I read numerous posts that this vac switch often goes bad due to the gear lube in the t-case getting sucked up into the vac lines. Is this correct? I would check this by taking out the switch and doing a visual inspection on it?

Is this the solenoid that you are talking about and what I asked what it was in my previous post? If it is, is there a procedure to check and see if it works?

 

The picture is quite small, but that looks like it.

When the vacuum switch fails, it allows transfer case fluid to get into the vacuum lines.

As far as testing the solenoid, I would start by testing that you have +12V across the connector when in 4HI. If you do, then plug in the solenoid. Next, determine which vacuum line runs to the transfer case switch and which runs to the front axle actuator. With the engine running, the vacuum line running to the transfer case should have vacuum. If it does not, then you have a problem at the vacuum switch on the transfer case. If it does, then hook it back up to the electric vacuum switch and remove the other line. If you have vacuum at the port where you just disconnected the vacuum line, then the switch is working. To verify, remove the electrical connection. It should close the valve, leaving no vacuum at the port to the front axle actuator.

 

I just went out with my multimeter, I didn't get any type of reading what so every but I can tell that there it power to the wire because whenever I touch the wires it sparks, I think I'm getting power from the TCCM, I will check tomorrow with a test light at the shop and put it up on a lift so I can get under and check the the vac switch an the t-case.

 

I'll have to look at one today but...I don't believe that this 'auto' optioned 4x4 system has a transfer case switch. I think you'll find constant engine vacuum going to the top most port and then at your command-vacuum continues thru after a 4 wheel drive command. So....check for vacuum to one(probably top)side, then thru it when eventually in 4wd. But if you don't have 12v to it...And forgive me for not reading thru all these posts but, did you ever change the dash switch? These are known to fail as I keep one in stock at my shop(indicating to me that it is a failing item). Keep us posted. JP