acdii

I can tell you it does as much as if you were driving in 4H all the time on a straight road. 4A engages from a dead stop, disengages during a turn unless slip is detected or more torque is called for (IOW don't floor it while turning), and disengages above a certain speed. Every time it does it requires more energy from the engine and will affect fuel economy. Driving with it in 4A all the time won't hurt the system, but you will see a drop in MPG. Just having the IWE engaged can affect MPG even if the system is not in 4A because it takes energy to spin the two axles, the front diff and the driveshaft, and whatever else may be spinning in the transfer case.

njrjammr

Thanks for the input. I guess I won't get to use 4A for quite some time. Southern winters 'n all. Maybe if/when I move back to upstate NY it'll pay off.

Florida_F150

Most people here in FL off-road and trail ride in the public Wildlife Management Areas. If you just want to play around a little with 4WD, I imagine there's probably something like that near you. It's free here, and if you go early in the morning, the scenery is beautiful. Just a thought...

D K

Two questions:

1. Is there such a diff in existanse that is a limited slip (torsen or clutch) that is ALSO a lockable diff?

2. Will the Torsen front diff from the Raptor fit on the F150?

Thank you.
David

klen

The owners manual recommends using 4WD occasionally to keep the gears lubed. Would using 4A occasionally accomplish the same thing?

Florida_F150

1) There are aftermarket products, such as those from Eaton, that keep your diff fully locked when going straight, and will automatically unlock as necessary when you're going around turns. Though that's slightly different than what you're asking. I'm not aware of any Torsen or clutch-based limited slip that ALSO locks, but maybe someone else can chime in.

2) Ford Performance makes a Torsen for the front diff of our F-150's that you can easily buy online. Not 100% sure if it's the exact same one used in the Raptor.

Florida_F150

If the gears they're referring to are the gears in the front differential, then yes, 4A would get those gears going as 4A would engage the front differential.

D K

Just because you have it in 4A, doesn't mean that the system is engaged. You would want to use 4hi to make sure it's engaged.

Wade88

Regarding the OEM locker on these trucks it won't let you keep it engaged unless you're creeping along somewhere around 20-25 mph above which it automatically disengages the locker. Therefore you can't drive down the highway with it on unless you are going criminally slow on the highway. Regarding leaving it 4a to keep the stuff lubed, it spins the fronts under power every time you accelerate from a stop in my experience unless you grandma it.

Florida_F150

Regarding 4A, I think most everybody is saying the same thing and in agreement. I looked into it and from what I've researched:

When in 4A, regardless of traction, the front hubs are engaged at all times (IWE vacuum is off, engaging the front hubs), the front axle shafts are spinning, the gears in the differential are turning, and the front driveshaft is spinning. This makes sense since activating all of that (turning it on and off in a split second every time the front needs power) would be impractical / impossible.

The Borg Warner transfer case in F-150's equipped with 4A monitors the traction front and rear and uses a clutch mechanism to send torque to the front differential as needed.