When my '07 F150 S/C is in 4WD Hi and I'm rolling to a stop, sometimes the truck suddenly grinds to a quick halt, othertimes it coasts (as I would expect). Also, at times, something seems to be resisting when going in reverse, as if I left the parking brakes on. This is also only when in 4WD Hi.

The dealer mechanics say this is normal but I'm still not convinced. Is this really normal operations?

Thanks,

 

This is not normal. Make sure that the emergency brake is disengaged. If so, it could be a problem with 4WD system. Could be vacuum, IWE solenoid, transfer case shift motor. Any time a dealer tells me abnormality is normal in my vehicle, I'll look for another dealer. Either your dealer is incompetent or they don't want to do any warranty work because they don't make as much on it and it takes longer for them to get paid for warranty work. In your case I'd say the former rather than the latter is true. At any rate, find another dealer. You'll be happier in the end.

 

are you doing this on pavement?


if so, DON'T EVER SHIFT INTO 4X4 ON PAVEMENT



if the symptoms exist on the dirt...no clue

 

Even truckless, tylus is dead on.

When you are in 4wd, you are locking the front and rear axles, forcing them to spin at the exact same speed. The problem is that whenever the front wheels aren't perfectly straight, the front wheels are going to have to spin faster than the rear wheels.

This puts the driveline in direct conflict of what your wheels are trying to do...the axles are trying to go at different relative speeds at the same time the driveline is forcing them to stay at the same speed. DON'T DO THIS ON PAVEMENT!!!

On dirt, grass, mud, gravel, snow, or any other surface that doesn't give great traction the tires will simply slip a bit and it'll still drive normally. The problem is that on pavement, the tires are very resistant to slippage, and this causes incredible amounts of wear on your driveline.

Remember the 4x4 system in your truck is NOT AWD! AWD is designed to allow for different speeds between the front and rear axles, so they operate without binding the driveline...your F150 isn't!!!

 

I usually use 4WD on snow or mud. I tested it a few times on wet pavement (trying to repeat the symptom). If my memory serves me, I was probably turning and it could have been on dry-ish pavement at the time I felt the symptom. But going in reverse was probably straight back only.

I'll keep these comments in mind next time I go into 4WD. It's great information and I really appreaciate your help.

 

no problem

wet pavement will help prevent the torque build-up a bit, but it's still a very risky endeavor to me.