Most of you are probably tired of me asking this, but I'm going to try another way of asking. I'm about to go junk yard shopping to make my 4AWD Expy able to be ran in true 2WD like the 97/98 years. I have no way of finding out a few things though. Did they use a different transfer case from 98 to 99? The difference I've seen from 98 to 99 is the obvious deletion of the 2WD on the switch, but also gone are the vacuum selonids on the fenderwell, and the vacuum motor on the front diff. I'm trying to further understand the system. Is the vacuum motor on the front diff called the Center Axle Disconnect (CAD)? I most need to know these 2 things: Is my 99's front axle and t-case the same as the 98? I realize that the GEM may be different but I'm not sure there either. I wish I knew someone here that has the rare 99+ Expy that included the 2WD option on the switch (there are a scarse few out there). Again I'm sorry if I've asked this too much, but I really want to start this conversion and I'm hoping I don't have to go into this without any sort of knowledge. Thanks everyone and I hope you all have a great New Years Holiday!

 

Your system is essentially a super-sized version of the one on the second-generation Explorers.

You can cut the brown wire that feeds the transfer case clutch coil. That will give you true 2 wheel drive.

Replacing the drivetrain components alone won't do it. In addition to the front axle, vacuum solenoids, and lines, you'll need a GEM and switch from the earlier model to control it all, which likely won't be compatible with the rest of the electronics it controls. It could be done, but it would take a lot of electrical work to make the GEM from the '97-'98 work with the rest of the truck, and it would be even tougher because the 99 also has the PATS system which may or may not play well with the older GEM.... It would be a lot of work to say the least.

To answer your question, no the front axle from a '99 is not the same as that one from the 98. The '98 is equipped with the center-axle disconnect, where the 99-up is not.

Heppy new year to you too!

-Joe

 

Thanks for repling, but from before I still can't find any brown wire lol. I've looked at everything I possibly could. Maybe I can use an electric tester to find out which wire feeds the t-case motor. Then I could put a switch like you've explained. As for the front diff, I got bored at work and pulled the plastic cover off the front diff, where the CAD was in the 97-98. There is a hole in the diff casing and the mounting bracket is there, just no vacuum motor. When you look into the hole, I see a metal thing that looks like it would get pushed in or something. I'm thinking I have the same axle as the earlier ones, but just need to get the motor and selonoids. I'm thinking maybe I could wire in my switch to activate the t-case when I want 4WD, and that switch could activate the vacuum motor on the front diff, this way I can have it true 2WD. Have you ever heard of 99+ with the 2HI on the switch. I swear to you, I drove a 00 Black E.B. Expy in 2002 and it had the 2HI on the switch. If that is the case, couldn't I get a GEM from one of those? I appreciate your patience with me asking this over and over, but I'm determined, lol

 

Oh, forgot to add why I want to add the CAD. My front end as it sits right now is engaged. If you lift the truck and put it in neutral, turn the front driveshaft the wheels turn. I want it like the 97-98 where if you turn the front driveshaft the front wheels won't turn. I have the t-case unplugged right now, but my steering and handling totally sucks. I want to be able to have true 2WD. Its funny, my 98 had that feature, but I'd never go back to that year because of the non P.I. heads and that hideous guage cluster.

 

There are a couple of simple ways to find the brown wire. The first would be to look at the plug on the transfer case. One of them is brown, guaranteed.

The second way would be to stop in at your local dealership parts department and ask them for a diagram that shows where the Torque On Demand or Transfer Case Shift relays are located. The brown wire will be connected to them.

If you pull the stereo surround out and remove the stereo itself, odds are it'll be back in that opening on one side or the other. If you were closer, I'd come look myself. It really is the simplest way.

Disconnecting the front axle at the CAD simply allows the front wheels to stop driving the diff carrier and ring gear. However, the front driveshaft still tends to turn because of the fluid shearing between the clutches in the transfer case. The only things that *may* stop turning are the front diff carrier and the driveshaft, and only then at low speeds. The CV joints and halfshafts turn all the time in both axles. Converting to an older front end with the CAD won't significantly affect any part of the handling. It *may* affect fuel mileage ever-so-slightly, but that would be a stretch.

For some reason, my '99 manual doesn't want to load up for me right now. Without being able to stare at both diagrams, I can't figure that out right now. I can double-check when I get back to work next Tuesday unless someone beats me to it.

My hunch is to think that the passenger side axle shaft is longer, eliminating the short lock-up shaft, collar, and pilot bearing assembly in favor of an axle shaft that engages the spider gear directly, but again, I don't have any way to know at the moment.

Here's the simplest way to get true 2 wheel drive: Unplug the transfer case connector. That will completely disable the front wheels from engaging. Take it for a ride, and you'll see that there aren't any significant steering or performance improvements. Disconnecting the passenger side axle shaft won't have a significant impact beyond that.

-Joe

 

Thanks alot, you most likely saved me alot of time doing something that won't do that much in the long run! I will keep searching for the brown wire, if I can't find it I'll get a voltmeter and find it that way. You are a big help, much thanks and Happy New Years!

 

Not a problem....

-Joe