4WD not engaging

[TBuzz]

Ok here's the issue and thanks in advance for any ideas. Went to climb some rocks and realized the front end was not pulling. I have a 2000 v6 auto with j shift 4wd. I recently replaced the front diff so I have had the add apart and the vacuum and electrical connections as well. Everything worked fine before, so it must be a result of my re installation. Here's the symptoms

1) while in 2wd and wheels on the ground the front driveshaft spins free
2) engaged in 4lo wheels on ground the front drive shaft will not spin
3) engaged in 4 lo N with front wheels in the air and the front wheels spin independently although the the driveshaft will not spin
4) engage the front air locker and the driver side tire will not spin
5) the 4wd light on dash does come on when I shift into 4H and 4L. Previously it only worked in 4L?

There is vacuum pressure that the VSV. There is vacuum at the actuator when I removed the hose. No change when reversed the hoses.

 

[TheDurk]

From your description, has to be the ADD actuator in the front diff. I don't see how the installation could cause those symptoms. The 'no change when hoses reversed' is the giveaway, assuming there is good vacuum on one side and not on the other.

 

[TBuzz]

Reading some of your other posts on this subject now. What would/could be wrong with ADD actuator suddenly? I was suggesting my reassembly and installation of ADD was incorrect.
I just went out and tried this. Turned on the truck and left it in 2wd. Switched hoses at vsv and drove back and forth half a block. Pulled back in jacked up driver side front and tire still spins freely from driveshaft.

 

[TheDurk]

Reading some of your other posts on this subject now. What would/could be wrong with ADD actuator suddenly? I was suggesting my reassembly and installation of ADD was incorrect.
I just went out and tried this. Turned on the truck and left it in 2wd. Switched hoses at vsv and drove back and forth half a block. Pulled back in jacked up driver side front and tire still spins freely from driveshaft.

I have no idea why but your actuator is not engaging.

 

[TBuzz]

Not what I was hoping you would say...this is the 2nd time I've had this front diff in/out of here in the last month. Previously when trouble shooting another issue it was determined that the driver side front tire was spinning with the driveshaft as I believe it normally should. The amount of vacuum at the manifold is loud and noticeable compared to at the hoses at the vsv and actuator. Is that normal or should it be about the same?

 

[TBuzz]

Driving in 2wd, then shift into 4H. Dash light comes on indicating 4wd. It doesn't feel like it is in 4wd when making turns in the dirt. While idling I switched the two vacuum lines at the vsv. Get back in the truck and the 4wd light is off. Same driving test and no apparent change. I put the hoses back the way they were shift back to 2wd, dash light is off and head back.

While pulling in I shift into 4h, then stop and 4L. Turn it off in park it, jack up drivers side front and tire spins freely from the driveshaft that is locked in 4wd. Start the truck and engage arb and the tire locks up. Disengage arb and the tire spins.

It seems my problem is that I don't have the add working properly. However when the ARB is engaged the driver side tire will lock up.

 

[TheDurk]

Driving in 2wd, then shift into 4H. Dash light comes on indicating 4wd. It doesn't feel like it is in 4wd when making turns in the dirt. While idling I switched the two vacuum lines at the vsv. Get back in the truck and the 4wd light is off. Same driving test and no apparent change. I put the hoses back the way they were shift back to 2wd, dash light is off and head back.

While pulling in I shift into 4h, then stop and 4L. Turn it off in park it, jack up drivers side front and tire spins freely from the driveshaft that is locked in 4wd. Start the truck and engage arb and the tire locks up. Disengage arb and the tire spins.

It seems my problem is that I don't have the add working properly. However when the ARB is engaged the driver side tire will lock up.

1. Seems to me driving on dirt is the worst way to test 4wd function. Either drive on asphalt where you can feel it bind in 4wd, or in something really soft like sand or mud where it will bog down in 2wd but not 4wd. On dirt it can be hard to tell as it will neither bind nor bog down. Maybe you should put all 4 wheels in the air so you can be 100% sure of what is going on (what I would do.)

2. I am not familiar with the ARB (rear-locker I assume) engagement system so I have no comment on this.

 

[TBuzz]

1. Seems to me driving on dirt is the worst way to test 4wd function. Either drive on asphalt where you can feel it bind in 4wd, or in something really soft like sand or mud where it will bog down in 2wd but not 4wd. On dirt it can be hard to tell as it will neither bind nor bog down. Maybe you should put all 4 wheels in the air so you can be 100% sure of what is going on (what I would do.)

2. I am not familiar with the ARB (rear-locker I assume) engagement system so I have no comment on this.

While in 4wd I tried to drive up a soft embankment and one rear tire just dug. I can't check the truck with all four tires in the air in my sloped driveway. The ARb is in the front diff and will only lock the front driver side. Does anyone know if I could have installed the actuator shift fork on the wrong side of the stub shaft collar? Preventing it from engaging?

 

[19963.4lsr5]

With the front wheel in the air and the XFR case in neutral spinning one wheel should spin the driveshaft. If not the problem is in the diff somewhere. (Your ARB install....)