A4h

[C LePoudre]

I have a 99 Exp with Automatic 4x4, and 4.6L.

The background: When I first bought the truck at auction it was stuck in 4x4 all the time when the selector was in A4H, but the 4x4 light on the dash was not on. I took it to the shop and some c-clips in the transfer case had been 'sprung' and I fixed them. All was good for a while.

The now: The truck now is stuck in 4x4 when you first start it up, until you get to about 60-70kph or so. You can then hear the 4x4 dissengage and the 4x4 light on the dash starts blinking, but at least it is now in 2wd. For short trips around town, I don't get to 60kph and being in 4x4 all the time is very hard on the truck and I suspect it would soon lead to the same problem I had when I bought the truck.

The solution(?): I suspect there's a problem with some type of slip sensor (pardon my ignorance). I had looked in the haynes manual when I first bought the truck, but don't remember the exact parts/sensor/switches that make up the system.

Any thoughts? Thanks in advance.
Chad.

btw: love my truck otherwise!!

 

[AvroAero]

The A4WD stops to function after a certain speed because 4wd at high speeds can be strenuous on the system. I'd say its in the 60kph area as you said. If your suspecting a A4WD problem you can disconnect the clutch temporarily by just cutting a wire and see if it continues. The light that blinks is it 4x4 or A4WD. I've only driven in one expy that had the option of 2hi,a4wd,4hi, and 4low and from what I remember there was a a4wd light in the dash.

How do you know its in 4wd besides the disconnect at 60k? Is there a different feel in the front with the drives hafts connected? Does it bind in turns?

If you disconnect the clutch you'll be able to rule the A4wd as possibly being a problem and focus more on the 4x4. FYI They connect the two drive shafts in different ways. The only possiblity that the A4WD could still have a factor is if the clutch is bound somehow, corroded. But I doubt that would be likely.

 

[C LePoudre]

The front end is binding when in A4wd. Note that my truck only has A4wd, 4H, 4L. Therefore, I don't have the option to put it in 2wd only. When starting the truck in A4wd, I have no 4x4 light and it is binding until about 60kph, then it dissengages 4x4, and the 4x4 light starts blinking. Once the 4x4 has dissengaged, I can drive around parking lots fine, until I re-start the truck (then back to binding again). Therefore, the truck will run in 2wd fine, but for some reason it always starts out in 4wd.

Thanks,
Chad.

 

[AvroAero]

Hmm. I'm not sure why it would lock at first and then not lock again, if thats so I would suspect that its either an electric problem or mechanical outside the transfer case. For some reason its giving voltage to lock em. Maybe theres a systems test, I can check some schematics.

 

[C LePoudre]

thanks.