I'm just curious to know if there's an easy way to tell if an Aerostar's all Wheel Drive is working properly. Of course it works some all the time. Will the 4x4 light come on when it's engaging? Is there a 'test' of sorts??

I remember reading where someone said they just found out theirs was not working in the snow one winter & I assume they got stuck because of it.

It just came to mind again as I was thinking how I had to disconnect the rear driveshaft to tow it again here in a few days. I wonder if it could be driven on front wheels only, asuming no oil would leak out the back with the rear shaft removed.

I've assumed it would have to lock the center 'diff' to do so, & that may not happen if the rear speed sensor is not going overspeed..??

Still, is there a test or evidence that the AWD is working right? I can't quite look out to see if all 4 wheels are spinning the same speed on a frozen parking lot can I?

 

If you are moving, it is working.


The Aero AWD is 100% full time 4wd. The transfer case is just like an open dif, if you disconect the rear drive shaft and try to move using the front wheels, you will go no where because all the power will try to go to the rear wheels.

The issue usually seen is the computer controlled 4x4 low (for lack of a better term.) Under normal driving conditions, you are running 70% rear/30% front power. Now when you are going 15mph or less and get stuck/loose traction, the computer kicks the ratio to 50/50 to help you get unstuck. The computer control for this is located under your drivers seat.

 

I'm guessing that as long as you don't see any 4X4 codes getting flashed at you, the AWD is working properly. You don't get any idication that the AWD is engaging while you're driving.

I've had my mine on jack stands and with the engine at idle, put it in gear, and slowly release the brakes. All four wheels will turn. If you're dying to find out if it works, that should work.

 

Well, I know all four pull. I can feel that. I did the in the air trick too once just for kicks.. shoulda made a video of it!

I thought it could direct up to 100% of the power to the front wheels if it needed to. Ill go back & read some old articles cuz obviously I don't know.

93Nighthawk, I dont think the center coupling is quite like an open diff. more like a computer controlled limited slip diff. I heard it was a fluid coupling, computer controlled. I think the computer locks it up more of less when it detects wheelspin. I wonder if it's same as full-time AWD Explorer. Probably similar. I appreciate the knowledge guys!

 

The center differential is not a limited slip in the same sense as the Traction Lock rear end that uses forces from the side gears to engage the clutches. The center diff uses an electromagnetically engaged clutch pack that's activated by the computer once it decides from the readings it gets from the various speed sensors in the transfer case that one end is losing traction. When it does this, the front and rear are equally locked together. But when it is not locked, it does behave as a completely open diff.

As someone mentioned, you can jack up all 4 wheels, you can see if the system is working. With the engine idling and brakes on, put the transmission in any gear, and release the brakes. At least one front and both rear wheels should turn; I think all E4WD vans have LSDs in the rear. You can carefully grab one of the front wheels to try to stop it, and the other should start spinning twice as fast as before; the front diff is completely open. If you disconnect the computer under the driver's seat, you can actually try to stop both front wheels, and all power will go to the rear.

 

I've studied a bit now & it seems the Aero E4WD must have a relatively conventional mechanical center differential (as opposed to fluid coupling) but with a clutch that I assume would be in the center between the side gears or more likely on the front of the diff locking the front output to the carrier. I'd like to see a diagram/ drawing of it.

Now that last thing you said xlt4wd90 is interesting! That with the AWD computer unplugged the front wheels stop being powered. So it could possibly be made into a part time system if that's true. I don't see how that could be the case .. but there's more yet for me to learn. Something has to be unconventional in that it can normally send an unequal amount of power to the rear.

I'm still searching online. I'd like to download the Ford Service Manual(s) but I'm not familiar with torrent downloads yet. I think that's the normal peer to peer file sharing strategy is it? Are there any conventional download sources for the 1997 Factory Ford Aerostar Shop/ Service Manual?

 

The design is an open differential, but it has planetary gears, which is what makes it rear biased when it is unlocked. There is always torque being split to the front. If the vehicle is off the ground, and the computer is unplugged, you can stop the front wheels from spinning, it is true. The system cannot be made into a part time system. If you say disconnected a driveshaft, the result would be that all the power would be routed to the driveshaft that has bee disconnected, so the vehicle will not move. If you activated the computer, the clutches in the lockup will burn out, since they will be forced to constantly adjust for the difference in speed and load.

The only way to make the system a part time is to replace the entire transfer case with a standard case, and all that that implies. It would require a lot of fabrication, and custom driveshafts.

 

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!)


There are many threads that explain the operation. Here is just one of them:

https://www.ford-trucks.com/forums/5...case-info.html

If you really want to get into some nitty-gritty look up SAE paper #892538.

 

Thanks Aerostar1 very much for the test procedure. I'm going to read that linked page now!

Thanks Bear River, being planetary may explain it.. I've no desire to make mine 2WD, just wanted to know more about what I was dealing with. In my short search I've found very little online about it. The Explorer had a full time AWD system too with no low range on some V8 models. It seems it would be a similar system.

 

The Aerostar and Explorer AWDs had similar systems. Both have transfercases with planetary differentials which split torque 1/3 to the front and 2/3 to the rear mechanically. They differ in the way the "lock-up" occurs when a wheel loses traction. The Aerostar uses a computer controlled electromagnetic clutch. The Explorer uses a Viscous Coupling Unit (VCU). The Aerostar system was supplied by Dana and the Explorer system was supplied by Borg-Warner.

 

Thanks again guys. Here's two linked articles in addition to this thread.

I didn't think to search this Aero forum yet, that would be too simple huh!?

The patent searches can get deep so I left those links off.

https://www.ford-trucks.com/forums/5...case-info.html

http://www.transonline.com/transDig...ards/index.html