Originally Posted by mikeyss
I personally feel Ford should have left the 2WD option on all of the Expy's. I had a 98 and drove it in 2WD throughout warm and non wet weather. 4AWD is nice when it is snowing or it is wet out. I now own a 99 Expy and it doesn't have 2WD option, only 4AWD, 4HI, and 4LO. I hate not having the 2WD option because it makes the steering alittle harder, on dry pavement when I have to merge onto the highway you can feel the front end engaging and disengaging constantly until I let off the throttle (I have the 5.4 and rear wheel spinning is common) so as the rear wheels try to spin the front end is engaging. I personally am afraid of the extra wear and tear of the t-case and front driveline. I have un-plugged the motor on the t-case and now it is running almost true 2WD. I am in the process of getting the vacuum diaphram so that I can un-lock the front axle like the 97 and 98 models. I have observed a slight gas mileage increase from un-plugging the t-case. The only thing I have observed by un-plugging the t-case motor is the 4x4 light flashes.
There's a much easier way than retrofitting the front axle.... more on that in a moment though.....
Let me clarify a few things. First, between the Explorer and the Expedition, we're talking about four distinct vehicles with three VERY different systems.
The basics. Control Trac is not the same thing as AWD. AWD uses a center differential (either viscous or gear-driven) to drive BOTH front and rear driveshafts at all times. The ControlTrac 4WD system is essentially "Rear-wheel-drive-until-it-slips" at which time the GEM engages the transfer case momentarily to drive all four wheels, then releases and checks for a slip condition again. It is AUTOMATIC 4 wheel drive
, not all wheel drive.
With the Control Trac System, the clutch in the transfer case is either on or off. There is no "partial" application of the 4wd in those systems. However, the GEM monitors the throttle position, vehicle speed, wheel speeds, etc to determine when 4wd is needed, and varies the duty cycle
of the transfer case clutch as it sees fit.
First, the Explorer. '95-96 model years with the V-6 used the Control Trac system in conjunction with a 2-speed transfer case and a center axle disconnect. The driver had their choice of 2wd, 4 auto, and 4 low.
For the '97-'01 V-6s, Ford did away with the Center Axle Disconnect and went to a live axle in the front in conjunction with the Control Trac system and the 2-speed transfer case. This gave the operator the ability to select 4 auto, 4 high, and 4 low.
All 4x4 V-8 Explorers from '95-'01 came with the AWD system, which uses a center differential and drives BOTH driveshafts at all times. The V-8s do NOT have a two-speed transfer case.
Now, with the Expeditions, for '99 (and '99 IIRC), they had four choices: 2wd, 4 auto, 4 high, and 4 low. These systems used a vacuum-actuated center-axle disconnect and a 2-speed t-case, very similar in design to the Explorer, essentially, just on a larger scale. In 2wd, the front driveshaft didn't turn, and the CAD was disconnected. In 4 auto, the CAD was engaged, essentially turning it into a live axle, and the automatic controls for the t-case were active (again, 2wd until the rears slip). In 4 high, the CAD stays locked, and the transfer case locked for a 50/50 power split front to rear. Of course, 4 low adds low range to the mix.
(As a side note, all the '97-03 F-150s used the same front drivetrain setup, but with a completely different transfer case)
In '00 (I think) they did away with the 2wd position on the dial, and eliminated the CAD on the front axle, again, essentially like the Explorer, only super-sized.
Disclaimer: I have not personally tried this mod on an Expedition, but the wiring schematics are identical to the Explorer, and should work.... in theory. Try this mod on the Expedition at your own risk (but I'd just about guarantee it'll work)]
Now, if you have a Control-Trac equipped vehicle (Explorer or Expedition) that is NOT equipped with a 2wd position on the switch, there is a way you can get true 2wd. It's known in the Explorer circles as the "Brown Wire Mod" and works wonders to get rid of the annoying clunking as it engages and disengages on dry pavement. You won't see any performance or mileage gains as the front wheels are still turning all the same components (halfshafts, diff, driveshaft, etc), it just prevents the transfer case clutch from locking the front and rear driveshafts together.