transfer case info
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Freshman User
Joined: May 2006
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From: southern colorado
transfer case info
My 93 4.0 Awd is chugging along nicely on its rebuilt cylinder heads I replaced last June.
When ford evaluated my van they said I had a bad transfer case elec. clutch, but I can lean out the window and watch my front wheels getting power.
I have heard all of the following:
the power is split 70-30.
Under some conditions it gets more power, half, all, it "locks to the front" ????
What actually goes on, what does the electric clutch do, and should I hear or feel anything when I purposely cause the van to slip and slide on snowy icy roads, which we have plenty of right now.
(It doesn't slip and slide much, it digs right in and goes!!).
So, enlighten me a little please.
Thanks, and happy new year.
When ford evaluated my van they said I had a bad transfer case elec. clutch, but I can lean out the window and watch my front wheels getting power.
I have heard all of the following:
the power is split 70-30.
Under some conditions it gets more power, half, all, it "locks to the front" ????
What actually goes on, what does the electric clutch do, and should I hear or feel anything when I purposely cause the van to slip and slide on snowy icy roads, which we have plenty of right now.
(It doesn't slip and slide much, it digs right in and goes!!).
So, enlighten me a little please.
Thanks, and happy new year.
Lead Driver
Joined: Sep 2003
Posts: 7,016
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From: SoCal
Normally, the center differential is open, and it splits the torque 30/70 f/r. There are speed sensors in the transfer case that are used by the 4wd control system to determine is either the front or rear wheels are slipping. I'm told that if it detects a speed difference of more than 5% between f/r, it will activate an electric clutch to lock the front and rear drive shafts, resulting in 50/50 split. So even if the control electronics are not working at all, you would get the 30/70 split, but in this case, if either end is on a totally slippery surface, it will spin helplessly.
Senior User
Joined: Feb 2004
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From: Rochester, NY
Because of the normal torque split, the rears are much more likely to spin then the fronts, especially considering the vehicle's weight distribution. But in the front was on ice and the rear on asphault, then the fronts can spin. If you can spin either axle for more then a second or so, then I'd bet the lock up clutch isn't working. When the clutch does lock up, the two axles are locked together momentarily. It holds the lock briefly, then disengages and looks to see if the spin condition reoccurs, relocking if necessary. IIRC, the clutch will disengage if you hit the brakes.
The real-world torque split when the clutch locks can be anywhere from 100/0 to 0/100, all depending on what the actual traction conditions are. 50/50 never really happens. If the rears spin and the clutch locks, the front is doing all the work and the rear is contributing next to nothing toward moving the vehicle. Thus, the actual torque split is 100/0, at least until the rears gain traction. Then it shifts as that changes. But the point is, during a lock, the torque split is dynamic rather then fixed at 50/50. Might seem like semantics to some, I guess, but this stuff is what I do, so to me the difference is significant...
The real-world torque split when the clutch locks can be anywhere from 100/0 to 0/100, all depending on what the actual traction conditions are. 50/50 never really happens. If the rears spin and the clutch locks, the front is doing all the work and the rear is contributing next to nothing toward moving the vehicle. Thus, the actual torque split is 100/0, at least until the rears gain traction. Then it shifts as that changes. But the point is, during a lock, the torque split is dynamic rather then fixed at 50/50. Might seem like semantics to some, I guess, but this stuff is what I do, so to me the difference is significant...
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Freshman User
Joined: May 2006
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From: southern colorado
thanks for the info. I'm starting to think I may not have the full capabilities of the transfer case.
I meant to ask where is some good repair/rebuild instructions, I never did buy the ford factory manual. I'd like to see some schematics etc..
I meant to ask where is some good repair/rebuild instructions, I never did buy the ford factory manual. I'd like to see some schematics etc..
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From: Rochester, NY
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Joined: Oct 2004
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A quick test for checking the operation of the T/C clutch: 1) Set the rear parking brake (Firmly). 2) Lift ONE front tire up so it can spin freely (use a floor jack under the control arm) 3) Start the van, put it in drive and take your foot completely off the brake (JUST LET IT IDLE - DON'T GIVE IT ANY THROTTLE) 4) Watch the raised front tire. If T/C is working properly, it will begin to spin and then stop every 3-4 seconds. If it spins continuosly, there is a problem. (Caution: The van could lurch forward during this test. Make sure there's nobody standing in front or near the van!)
I think mine needs new heads too. What problems lead you to replace them?
I think mine needs new heads too. What problems lead you to replace them?
Last edited by Aerostar1; Jan 12, 2007 at 11:22 AM.
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Freshman User
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From: southern colorado
Hi, Aero1
I think I shared your pain, with the coilpak purchase.
My 93 4.0 was running poorly, missing etc. tried the various things, same as you did, if I recall correctly.
When I did a compression test I discovered almost zero comp on one cyl, 85 # on another, so with Chilton in hand I pulled the heads. The head shop said I was running a very rich mixture and it caused the valve seats to practically disappear.
On a 4.0, I would say it was not as difficult as even Chilton made it sound.
Thanks for the info in the transfer case, and if You go for pulling your heads I'm sure this forum will have plenty of help.
Coldgeorge, and I mean -2 degree cold.
I think I shared your pain, with the coilpak purchase.
My 93 4.0 was running poorly, missing etc. tried the various things, same as you did, if I recall correctly.
When I did a compression test I discovered almost zero comp on one cyl, 85 # on another, so with Chilton in hand I pulled the heads. The head shop said I was running a very rich mixture and it caused the valve seats to practically disappear.
On a 4.0, I would say it was not as difficult as even Chilton made it sound.
Thanks for the info in the transfer case, and if You go for pulling your heads I'm sure this forum will have plenty of help.
Coldgeorge, and I mean -2 degree cold.
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Thanks for the info on the heads.
In your original post you asked if you could hear or feel the T/C clutch kicking in. Not always. It is very quick and kicks in after only a half revolution of a slipping tire. For kicks, hook up a 12 volt buzzer or light to the wires that power the t/c clutch (see schematic on page 2: http://www.transonline.com/transDig...ards/index.html). The control module is under the driver's seat. Get a couple piggy-back connectors and tie into wires 13 and 14. When the clutch kicks in, the buzzer/light will let you know. It is also good to know that it is NOT coming on on pavement when it is not suppose to.
In your original post you asked if you could hear or feel the T/C clutch kicking in. Not always. It is very quick and kicks in after only a half revolution of a slipping tire. For kicks, hook up a 12 volt buzzer or light to the wires that power the t/c clutch (see schematic on page 2: http://www.transonline.com/transDig...ards/index.html). The control module is under the driver's seat. Get a couple piggy-back connectors and tie into wires 13 and 14. When the clutch kicks in, the buzzer/light will let you know. It is also good to know that it is NOT coming on on pavement when it is not suppose to.
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Joined: Sep 2003
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From: Southern California
Originally Posted by rebocardo
FWIW: On the supplied link, I thought the Dana 28 was the front axle and not the transfer case ...
Post Fiend
Joined: Apr 2005
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From: Washington state
the TC is not rated nor designed for full time 50% front/50% rear lockup...something will break....
that's why the electronic controller under the seat cycles the lockup on and off every three seconds to relieve bind up forces
need an open diff in the TC most of the time
the LC is only for the worst of the worst
forget the switch on and something will break....the Dana 28 TC is almost unobtanium now and is far more expensive to rebuilt than common TCs
put on aggressive lug narrow tires 215 or 8.50 and the AWD Aero in 30/50 normal open TC operation will take you anywhere until the monster belly pan bottoms out or the low aircraft deck size A arms drag up a ton of mud
that's why the electronic controller under the seat cycles the lockup on and off every three seconds to relieve bind up forces
need an open diff in the TC most of the time
the LC is only for the worst of the worst
forget the switch on and something will break....the Dana 28 TC is almost unobtanium now and is far more expensive to rebuilt than common TCs
put on aggressive lug narrow tires 215 or 8.50 and the AWD Aero in 30/50 normal open TC operation will take you anywhere until the monster belly pan bottoms out or the low aircraft deck size A arms drag up a ton of mud
Last edited by 96_4wdr; Jan 17, 2007 at 07:01 PM.
Former ******
Joined: Nov 2004
Posts: 4,901
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From: Salt Lake City, Utah
The AWD on these really does work remarkably well. I have no problem going in the snow or ice. Stopping is often a challenge however. Especially with a 2,000 lbs trailer behind you. LOL
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