I've got a 97 4.6 standard with the manual t-case and 3.55 gears, I do 75 miles of hwy driving a day so I do not want to put lower gears in it.

I pull my ski boat all summer which is no problem until the campground, where I either end up smoking the clutch or spinning the tires backing in a campsite or pulling up the boat ramp

I posted a while back about twinsticking it and was directed towards a posi-lok system which would allow for 2wd low while at the campground. In lieu of spending $160, I researched the 4wd system on my truck and traced the ins and outs of it.

What I came to was the actual vacuum actuators that are mounted on the top of the passenger firewall underneath the hood that engage and disengage the front axle. It is much like the quadratrac 4wd system on a 79 CJ7, only instead of a switch it gets an electrical signal to open or close the actuators.

There are 2 actuators with 2 wire plugs and 2 vacuum lines coming from each. I unplugged the harnesses from them and had 2wd all weekend while at the lake and it worked like a dream

I decided that the best plan of attack to achieve a 2wd Low without having to unplug these harnesses each time would be to cut the wires and run them to a switch inside the truck. By doing so I could shift to 4wd lo and actually be in 2wd lo until I flipped the switch to send the signal to the actuators to engage the front axle and effectively engage 4wd.

MY PROBLEM:

I had a friend shift through the t-case gears while I held a test light to the 4 wires to see which were getting signal at each stage in the shift so I would know how to wire the switch. When I did so, each actuator had a wire that stayed constantly hot no matter if it was in 2wd, N, 4 Hi, or 4 Lo. And each had a wire that was never hot. So I don't understand how it's getting a signal to engage the axle or how I need to wire the switch.

Has anybody attempted this mod, or does anyone have a schematic showing these wires and where they get their juice?

 

I would also like to know this. I love the power 4 low gives when backing and or moving a trailer in tight places but don't like putting the strain on the drivetrain when turning on pavement.

 

so, the wire that you say is never hot is the wire you would want to put the switch on, it is a ground wire, like most wiring systems now, when you turn something on such as dome lights, actuators, etc., the computer sends a ground signal to the device making it run, so basically it runs off a ground. so on the wire that is never hot, if the key is turned on and you put a wire from the - terminal on the battery to it then the front axles will engage. so put a toggle switch on that wire, and you should be good to go.

 

Ok, but there's 2 actuators. So what should be happening here is 1 actuator gets the signal to engage the axle so it opens up and pulls a vacuum to engage it. When you shift back to 2wd, the other gets the signal and pulls vacuum to disengage it.

So essentially I need a 3-way toggle..... On-off-on. I need to ground the toggle and run a leg to each actuator, and the off will never actually be used.

Sound correct?

 

sounds like it should work

 

Sweetness!
Keep us posted as to your progress.
I was getting close to ordering the posi-lok, but I like this idea better.

I need 2wd low for the same thing...steep *** boat ramps, and jockying it around on our property to park it.
My 89 is no problem with the manual hubs, but this 98 is a different animal.

 

Yea, I'm looking forward to doing it before July 4 when I'll be back at the lake. Im broke right now so I'll have to wait till pay day Friday to buy my $5 toggle! And I'm working on putting a sub in my mastercraft. I'll let you know how it works when I do it.

I tested it today with a test light. Ha it hooked to positive on the battery and had a buddy shift from 2-4 and sure enough it's a ground that gives it the signal! I think it will work like a charm! $5 is waaaay better than $160 IMO!!

 

Interesting thought (2L), I'm wondering if I couldn't do the same thing except leave my manual hubs unlocked. I do like the gearing in low axle for my slow and go trail rides. I'll have to give it a try.

 

^^^If you have manual hubs, you're golden.
As long as they aren't locked in, you can drive around in 2wd low range all day long.
(That's the point I was making about my '89 with manual hubs)

 

Good to see more and more people are finally starting to actually mod these trucks. Great idea, pave the way my friend