Normal 4WD Hi operation?
Thread Starter
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2nd Gear
Joined: May 2009
Posts: 2
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Normal 4WD Hi operation?
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,
The dealer mechanics say this is normal but I'm still not convinced. Is this really normal operations?
Thanks,
Postmaster
Joined: Jul 2008
Posts: 2,565
Likes: 2
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.
MMNC (SS)(Ret)
Joined: Mar 2004
Posts: 11,607
Likes: 151
From: SE Georgia
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
if so, DON'T EVER SHIFT INTO 4X4 ON PAVEMENT
What you are experiencing is Driveline Torque. The wheels are getting bound up...this is caused by the tires inability to "hop, skip, spin, jump" like they can off-road.
This torque is developed quicker when turning. In a straight line, virtually no torque is created...but crank the wheel slightly, and you'll feel it.
So Torque builds up...and sooner or later, something will break
This torque is developed quicker when turning. In a straight line, virtually no torque is created...but crank the wheel slightly, and you'll feel it.
So Torque builds up...and sooner or later, something will break
if the symptoms exist on the dirt...no clue
Super Moderator
Joined: Aug 2003
Posts: 25,479
Likes: 742
From: Isanti, MN
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!!!
, 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!!!
Thread Starter
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2nd Gear
Joined: May 2009
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Likes: 0
Thanks for the replies
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.
I'll keep these comments in mind next time I go into 4WD. It's great information and I really appreaciate your help.
