Hello all;

Searched the forums (and Google) and haven't found a mention of this issue, hoping someone here has.

I have a 2008 F150 Limited (which has AWD like the Harley Davidson). The truck is NOT regular 4WD - the AWD is constantly engaged.

Lately, the 4x4 HI light has been flashing and I have noticed the front wheels are not engaging - now that we've gotten some snow the rear wheels have been spinning up hills. Last winter the truck absolutely hooked up in the snow - now its spinning like a regular rear wheel drive truck.

The ABS light is not coming on - which makes me think it is not the rear wheel sensor. I may change that first, but I don't think the sensor is bad - they are just magnets and don't go bad too often. But its an easy/cheap fix so I may start there.

Any opinions/advice? Anyone see this behaviour before?

Thanks, Steve.

 

Does it flash 6 times every 2 minutes

 

Yes it does (was going to post that, but forgot - the indicator light is hidden by the steering wheel). It actually flashes 10 times (definitely not six). I didn't time it but that happens about every two minutes.

 

Check the 20A fuse under the hood..there's a small fuse box on the fender well.

 

Does the AWD system still have IWE's ?

 

I will check the fuse later today. Fuse 29 and 30 in the passenger compartment were fine - they are related to the AWD system.

No IWE's, so I don't believe its a vacuum problem. From what I can gather, the AWD uses an electrical system to transfer power to the front wheels when it detects slipping in the rear. The truck does have an AWD/4LO selector, but that doesn't seem to do anything now (previously it worked).

 

Only a 5A fuse under the hood in the small fuse box. A couple of AWD relays in there as well - checking them but I doubt they are the problem.

No resolution yet - truck goes into the transmission shop tonight.

 

Transmission shop diagnosed the problem as a transfer case issue - there is a clutch in there that is electronically activated to transfer power to the front. Clutch is done.

This was *likely* caused by different sized tires on the front and back - this is definitely an issue with AWD vehicles. The tires are different brands but within 1/2" of being the same circumference - I though that would be OK (I guess not). Expensive lesson to learn.

 

Ouch Always run the same size tires. According to this about 1/2" in circumference makes a difference of about 16 revolutions per mile! That's going to put a long of stress on it!


https://tiresize.com/comparison/

 

There you have it.... big no no for AWD vehicles.