01 ford expy question(regarding A4wd)

[01fordeb]

Iv got a question about the brown wire mod. Well a couple questions. 1.Does it help mpg? 2. Can you still lock it in 4x4 or 4x4lL 3. Does it help wear on the tranny. Sometimes when I back up a hill or the back tires spin it has a screeching sound like its slipping or something were it try's to lock in.

 

[99 Expy]

1. It won't help your mpg, because your truck is in 2wd until the a wheel slips and the 4x4 is automatically activated.
2. You will still be able to go into 4hi and 4 lo
3. I'm not sure exactly what how the 4x4 engages, but from previous threads, I think I remember that there is something in the front axle that locks when put in 4x4 or A4x4. The transfer case also locks in when in 4x4 or A4x4. Whatever the parts included that lock in when the A4x4 is activated, I would think you save wear due to them not locking in while the parts are in motion. I'm sure that if they have the A4x4, it must be "safe" but IMO, if you aren't able to turn a switch to put it in 4x4, then you shouldn't have one, especially when its shift on the fly.

 

[tonydiv]

There is a center axle disconnect on the gen 1 trucks that disengages the right side axle shaft. That allows the spider gears in the open differential to turn without turning the entire ring gear. (which would also turn the driveshaft and cause quite a bit of drag)
If it fails to engage (like my truck is doing now) the driveshaft spins in 4wd but no power gets to the wheels. If it partially engages, you would probably hear some grinding / poping from the front.

This setup is also the reason that you can't put a limited slip diff in the front. Only a selectable locker will work.

The later trucks have IWEs (integrated wheel ends) that are more like an automatic version of the old style 4x4 hubs

 

[99 Expy]

I knew it was something like that, I wish they were lockouts though, I like mechanical parts more than electrical

 

[toms89]

The front differential in the 1st generation expys is a standard 8.8 open differential. There is no magic in them. Whenever the expy is moving it spins the front differential along with the front driveshaft. The transfercase is what engages and disengages the 4wd. You can install a locker or traction lock unit up front but it is not advised and the factory would never do it. If you are in 4wd and 1 of the front wheels looses traction it can jerk the steering wheel right out of your hand. Most hardcore 4wd guys are aware of this and prepare if they installed a locker. This is not a issue with an open diff.

4wd's with lockable hubs are able to disconnect the front diff and driveshaft.

 

[01fordeb]

1. It won't help your mpg, because your truck is in 2wd until the a wheel slips and the 4x4 is automatically activated.
2. You will still be able to go into 4hi and 4 lo
3. I'm not sure exactly what how the 4x4 engages, but from previous threads, I think I remember that there is something in the front axle that locks when put in 4x4 or A4x4. The transfer case also locks in when in 4x4 or A4x4. Whatever the parts included that lock in when the A4x4 is activated, I would think you save wear due to them not locking in while the parts are in motion. I'm sure that if they have the A4x4, it must be "safe" but IMO, if you aren't able to turn a switch to put it in 4x4, then you shouldn't have one, especially when its shift on the fly.

Ok, Im asking if i cut the wire. the a4wd wouldn't work, is that right? But I can still use 4wd and 4wdl

 

[toms89]

Ok, Im asking if i cut the wire. the a4wd wouldn't work, is that right? But I can still use 4wd and 4wdl

I am speculating here based on viewing the transfercase schematic. I have not actually done this mod but hopefully others that have can confirm.

You loose all 4wd functions if you cut the wire as you are cutting power to the transfer case magnetic clutch. You need to put in a switch that you can readily access to do this mod. There is only 1 clutch in the transfer case and in A4wd mode the GEM controls it. If you select 4hi you lock it on. If you cut that brown wire neither can engage it. The 4 low selection controls a shift motor plus the clutch is engaged via that brown wire.

 

[toms89]

I would cut mine to confirm as I plan on doing this mod...... but it currently raining here.

Been raining here seems like every other day or more...... sucks!

 

[tonydiv]

The front differential in the 1st generation expys is a standard 8.8 open differential. There is no magic in them. Whenever the expy is moving it spins the front differential along with the front driveshaft. The transfercase is what engages and disengages the 4wd. You can install a locker or traction lock unit up front but it is not advised and the factory would never do it. If you are in 4wd and 1 of the front wheels looses traction it can jerk the steering wheel right out of your hand. Most hardcore 4wd guys are aware of this and prepare if they installed a locker. This is not a issue with an open diff.

4wd's with lockable hubs are able to disconnect the front diff and driveshaft.

Well sort of... The front drive shaft does not turn unless the transfer case is in 4wd. The reason that the diff is open and the right side axle gets disconnected is so that the spider gears in the diff can spin without spinning the whole differential. If you left the right side connected, it would, then spin the diff and driveshaft. The whole design is made to keep drag down to a minium when in 2wd. Since mine is acting up, I had the center axle disconnect locked in this winter and my mileage was "affected" to say the least.


Because of the design of the front end, it would be really difficult and expensive to make all the parts change it over to good old fashioned lockable hubs. That's why there are no kits commercially available, you're just better off doing a solid axle swap.


The newer IWE setup isn't perfect either, they are vacuum operated and don't positively "lock in" so you really can't ever be 100% sure that you actually have 4 wheel drive.

 

[01fordeb]

Rain is a good thing But for now I took a fuse out from under the hood just now and its number 104 and all 4x4 functions don't work. but it's a 2wd, and dragging axles,I suppose. If I ever need 4wd I have the fuse in a box in the back, So all good, no need to cut wires, run wires and switches

 

[Racenut]

I am speculating here based on viewing the transfercase schematic. I have not actually done this mod but hopefully others that have can confirm.

You loose all 4wd functions if you cut the wire as you are cutting power to the transfer case magnetic clutch. You need to put in a switch that you can readily access to do this mod. There is only 1 clutch in the transfer case and in A4wd mode the GEM controls it. If you select 4hi you lock it on. If you cut that brown wire neither can engage it. The 4 low selection controls a shift motor plus the clutch is engaged via that brown wire.

NO YOU DO NOT LOOSE ALL OF THE 4WD FUNCTIONS! 4H AND 4L STILL WORK NORMALLY!

The only thing that you loose is the A4wd. Where you have to be carefull is which wire you cut, becuase there is a Brown and a light brown wire. YOU NEED TO CUT THE LIGHT BROWN WIRE for this mod to work. If you cut the Brown wire then yes you will loose 4wd completly.

 

[toms89]

Well sort of... The front drive shaft does not turn unless the transfer case is in 4wd. The reason that the diff is open and the right side axle gets disconnected is so that the spider gears in the diff can spin without spinning the whole differential. If you left the right side connected, it would, then spin the diff and driveshaft. The whole design is made to keep drag down to a minium when in 2wd. Since mine is acting up, I had the center axle disconnect locked in this winter and my mileage was "affected" to say the least.


Because of the design of the front end, it would be really difficult and expensive to make all the parts change it over to good old fashioned lockable hubs. That's why there are no kits commercially available, you're just better off doing a solid axle swap.


The newer IWE setup isn't perfect either, they are vacuum operated and don't positively "lock in" so you really can't ever be 100% sure that you actually have 4 wheel drive.

Is yours a stock unit? Its not in any of my exploded views of the front differential or passenger side front axle nor is it ever mentioned in the complete shop manual. To me this really makes no sense. Where is this disconnect located on the front driveshaft?

 

[toms89]

NO YOU DO NOT LOOSE ALL OF THE 4WD FUNCTIONS! 4H AND 4L STILL WORK NORMALLY!

The only thing that you loose is the A4wd. Where you have to be carefull is which wire you cut, becuase there is a Brown and a light brown wire. YOU NEED TO CUT THE LIGHT BROWN WIRE for this mod to work. If you cut the Brown wire then yes you will loose 4wd completly.

Thank you for setting me straight racenut I checked the transfercase and there are many wires coming out. I see one tan wire from a large connector and the case..... would this be it? It is on the outside corner of the electrical connector.

 

[toms89]

TonyDiv.

I found this after researching online for sometime. It seems the 97 & 98 expys have this feature to which you are refering too but the 99-2003 do not. Don't know about later models. Of course this is based on other online "experts" statements so take it as you may. But this makes sense to me as my shop manual covers 2000-2002 and I know my 2000 expy does not have this feature. I found a 1997 ford f150 front axle assembly exploded view that shows this feature to which you are refering.

First picture is 2000-2002
Second is 1997 F150

So I apologize for doubting you. I should not have made generalizations based on my expy but it appears we both may be correct for our particular expys. I learned something new today!

I tried to add the matching label and description info but the files were too large to upload

 

[imported_sdaviddr]

This could help or confuse you even more.This is from a explorer site, but the transfer case operations are basically the same.I did this to my explorer.

http://www.explorerforum.com/forums/showthread.php?t=149388

 

[toms89]

This could help or confuse you even more.This is from a explorer site, but the transfer case operations are basically the same.I did this to my explorer.

http://www.explorerforum.com/forums/showthread.php?t=149388

Quoted from article : " '95-'96 (Switch says, 2WD, 4auto, 4 low)

The system used in the early second generation Explorers was very similar to the later second gens. The '95 and '96 model years used the same transfer case as the '97-01 in conjunction with a Center-Axle Disconnect on the front axle. In 2wd mode, the transfer case is unlocked, and the CAD essentially breaks the passenger side axle shaft between the front differential and the passenger side halfshaft. That allows the front differential to stop turning, leaving the driver's side wheel to drive only the spider gears inside the diff.

When you engage 4auto on a '95-'96, the GEM switches the signal to a vacuum solenoid (insert picture here) which locks the CAD, thereby connecting the front half of the drivetrain and forcing the front driveshaft to turn with the wheels. Then, when the GEM determines that the rear wheels are turning faster than the fronts, it momentarily locks the transfer case, linking the front and rear driveshafts together for a period of time. The GEM then unlocks the transfer case, checks for slipping again, and, if necessary, locks the transfer case again. This produces some clunking and unconventional engagement and disengagement that many people don't like."

This right here clears it up for me. According to article the front axle is disconnected only while in 2wd mode. If the later gen 1 expys have no 2wd mode selectable then what would be the point for ford to put in a center axle disconnect that would never be activated. Thus the reason why later gen 1 expys with no 2wd setting have no center axle disconnect to which tonydiv was refering.

 

[imported_sdaviddr]

What would the point? To have fun! You can't go sideways around a corner on snow or gravel roads with a A4wd (auto).If you cut the brownwire and put in switch,you can.The best way to find that brown wire would be to look at the transfer case. Near the front driveshaft is one brown wire all by itself coming out of the case,thats the wire that can be cut.

 

[01fordeb]

And you can also remove the front drive shaft all together for summer months and put it back when needed, I just removed my fuse so its a 2wd, it feels better when you pull out now to.

 

[imported_sdaviddr]

Yea, you can do that too,but what happens if you are driving some where and you find a cool place to play around in.

 

[toms89]

What would the point? To have fun! You can't go sideways around a corner on snow or gravel roads with a A4wd (auto).If you cut the brownwire and put in switch,you can.The best way to find that brown wire would be to look at the transfer case. Near the front driveshaft is one brown wire all by itself coming out of the case,thats the wire that can be cut.

sdaviddr

I edited my previous post to try and make it clearer as to what I was saying. I was not asking why not have 2wd.