Didn’t want to hijack Sous' thread so, finally got around to doing this yesterday but....it doesn't work on my truck, the problem is not with the mod, it's something else. Everything seems to work as it should with the ESOF, in 2WD I can rotate the front drive shafts by hand & when in 4WD hi or lo it's all locked in as it should be. But it all stays locked either using the new switch or even disconnecting the plug fom the vacuum solenoid, very strange. AFAIK everything is as it left the factory so today I will try to investigate further. Any pointers would be welcome.

 

I pretty sure with the mod the driveshaft will still be locked in, it just disables the hubs from locking in like having manual locking hubs. I got rid of the auto hubs and went to warns so I didn’t need the mod with button, but my front shaft will still lock as you are taking about. This dosent matter as long as the hubs are free you won’t have any binding as it’s not really 4x4 without the hubs locked. Now if your hubs are locked in as well with the pump unhooked then you have more issues with the hubs themselves I think.

 

That's the issue, the hubs are free when in 2WD & the shafts spin freely as they should, but selecting 4x4 everything engages (as it should) I can't understand why it's like this. If the hubs were stuck engaged it would make sense but they're not, they engage as & when they should, but unplugging the vacuum solenoid has no effect. Confusing isn't it!

 

The shafts should be locked by the transfer case. If the hubs were free before you disabled the vacuum solenoid, they will remain that way. Did you try jacking up one of the front tires to check the hubs?

 

^^^^^^This but just spin the wheel and see what happens. All the mod does is stop the hubs at the end from engaging, the transfer case still goes to 4X4. Also you can check another way...when in 4X4 you get that binding when you turn (I think that we all know that feeling). Activate the mod, turn on your 4X4 and see if it binds or not.

 

Ok update, just spent the last hour going over everything, all works as it should apart from the mod switch, disconnecting the vac relay does stop the hubs from engaging, but the switch (in the earth wire as per Sous' thread) has no effect. I think that part of the trouble I thought I had is that the hubs don't disengage if they are under a bit of load. I will try a different switch next, this one did check out ok with a meter but who knows? I'll let you know how it goes.
BTW, thanks for your help with the car parts Mark, I've been quite busy of late & can't remember if I'd messaged you since they arrived.

 

No, hadn't heard, hope they suit you well.

 

I find this very strange because I verified that this mod works several times at several locations. For example, when leaving the driveway after performing the mod, I checked it there. Drove about 8 miles to a parking lot, checked it there. Drove about 10 miles to another parking lot, checked it there.

When the switch is in "hubs auto" (as it was from OEM) the hubs will lock when I change the selector switch to 4 Lo. I verified this by going forward and backward about 30-40 yards and attempting to spin the front shafts by hand, they did not spin freely. I also verified free spinning by performing a tight circle turn on pavement to check for binding, there clearly was binding so I did not push it very far into the turn.

When the switch is in "hubs manual" the hubs did not lock when I change the selector switch to 4 Lo. I verified this by going forward and backward about 30-40 yards and attempting to spin the front shafts by hand, they did spin freely. I also verified free spinning by performing a tight circle turn on pavement to check for binding, there was none.

I did this test 3-4 times at each location and had consistent results based on which position the new auto/manual switch was in.

If your new switch does not produce the results you are looking for, try this. Put everything back to OEM and then verify your 4x4 is working properly by performing the rolling test I did above. If it is working properly, go under the hood and unplug the solenoid with the 3 wires to it and try the same test again. See what the differences are.

What year is your truck?

I don't think there is a difference between the years in regard to 4x4 and actuation of the hubs, but maybe there is.

Are you sure you tapped the switch into the right ground wire?

I am interested to see what you come up with because I would hate to be providing inaccurate information on how to perform a modification. This is strange because it works perfectly on my truck.

EDIT: Just thought of something else. From time to time you will have to roll the truck forward or backward (kind of like the old days of locking in hubs) in order to get 4x4 Lo to lock in or release. This did not happen during my testing, but has happened in the past. Every once in a while on the FTE you will see where people think they are stuck in 4x4 Lo, but they find out later that rolling the truck a bit will remove this condition after going to hi and to 2wd. I think this procedure is even in the manual, but not sure.

 

Truck is a 2000 (built 11/99), yes not allowing the hubs to disengage was confusing the issue, the hubs don't lock with the vacuum relay plug removed, but with the switch in the grey/black wire the hubs still lock regardless of the switch position which makes no sense, I won't get a chance to look any further until the weekend now, I am determined to resolve this as it's a must have mod for me. Thanks for your input.

 

Well, my truck was built in 12/99, so that rules out the being different thought.

I am determined to help you resolve the issue too.

OK, so I have another idea after reading your latest statement.

Put everything back to OEM and make sure the hubs lock and unlock as they should. This will give you/us a good starting point a reference that everything is working properly.

Then, break the ground wire somehow with either connectors that are unplugged or taping the ends so they don't connect or ground. Now, test the operation of the 4x4 again and ensure that the hubs are not locking. This will not only tell you something after (toward the new switch) is not right and that the breaking of the ground wire is working as intended in regards to a modification.

If needed, I can check the gauge of the wire I used and you should have the type of switch I used in your notes from my original thread. I don't think that those components should make a difference, but I don't know this for sure.

I was confident that this mod would work because I sought advice from a couple of different electrical engineer type people and they confirmed this was the best and safest method of accomplishing the mod. Other than getting under the hood and removing the plug of course.

I apologize for not seeing this until Monday afternoon your time, it must have slipped by me yesterday.

 

I have already verified that everything works as it should when all stock, the switch that I have used is rated at 10 amps & the wire is rated for 15 amps (we use different units for guage here as I'm sure you know), the switch is a new item that I tested with a meter before installing but I haven't ruled it out yet! I'm renovating our house for the next few weeks so we are camping at a local campsite while I tear the house apart which limits any spare time to investigate further, but I'll let you know how I get on. Do you know of a resource for a wiring diagram for the ESOF?

 

I read earlier you had tested everything to ensure 4x4 was working properly, I was saying to do it again to make sure we are back at a good reference point or "zero" before moving forward.

At this point, I would break the connection on the black ground wire by any means you see fit and test the 4x4 function. There should be none because the black ground wire completes the circuit for the other two wires. With the black ground wire simply cut and/or separated tape or secure the ends so they don't ground with anything and try the operation of the 4x4.

This is all the switch is doing is making and breaking the ground connection.

As for a diagram for the ESOF, this is all I have/had.

 

Thanks, that gives me something to look at, I'll recheck it all next.

 

Sous, I have a question for you...if you put it into 4X4 first, then hit the mod switch, will the hubs unlock?

 

You beat me to it!

It is my belief that the mod only stops the hubs from being actuated by the vacuum pump.

This means they will remain in their last position.

I recall the activation of ESOF is only for a short period, as evidenced by: if you're stuck and they don't go in right away, they won't go in later.

In other words, ESOF isn't a "vacuum hold in place" rather a pulse and lock if they can.

I recall they also pulse differently to disengage.

I'd like a "Really Danged Stuck" switch that you could hold and it would continuously try to engage ESOF as you rocked the truck a bit to help them engage.

I've been bitten by that one right after getting our Excursion