4 Wheel drive question.

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I am not that familiar with 4-wheel drive. Any help would be appreciated.
My wife bought a 1995 F150 4x4. We noticed something with the four wheel
drive and brought it to our mechanic.
With 4-wheel drive engaged, sharp left or right hand make the steering feel like one of the front tires is flat. Going straight or taking minor turns is fine. Driving on snowy roads is fine -- sharp turns or going straight.
Our mechanic inspected the trucks front end and four wheel drive and believes there is nothing wrong. He drove the truck and was able to reproduced the problem. His recommendation was to only engage the 4 wheel drive on wet/snowy surfaces.
Is this to be expected or is something wrong?
Thank you in advance.
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All full sized Ford Trucks will do the exact same thing on dry pavement. You should never engage your four wheel drive on dry pavement, even on straight roads!

feel
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All four wheel drive vehicles will do that, not just Ford trucks.

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4 wheel drive is not designed for dry roads. what you are feeling is the locking front differential trying to turn both front wheels at the same time when you turn.
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The front end operates on different radius' than does a rear end. The wheels on the solid rear end are rotating on the same radii with the outside wheel turning more RPM to do so. The front wheel when turning must do so on two different radius and following two distinct radii at each axle end. When not powered the outside wheel is free to turn at what even RPM's is necessary to follow the inside wheels radius. When engaged, even though their is a differential, that is not the case and the interior wheel making the same turn in a smaller circle must scrub. That scrubbing is called rap-up. On loose surfaces it is permitted to un-wrap by slipping, but not on a dry surface.
mike hunt
Falcoon wrote:

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In other words:
The truck is trying to turn the front and back wheels at the same speed... and can't because the front and back wheels don't turn at the same speed during turns.
I can't believe they actually inspected the truck! This is a very common 4X4 knowledge.
You have part time 4 wheel drive, which means you should only use it part time. To get un stuck or while on slippery road surfaces only. They do have full time 4 wheel drive vehicles as well. The front and rear axles are not mechanically locked together in these type vehicles.
So you don't get the hop during tight turns.
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That is called drive line bind, and if you do it enough you will cause expensive damage! DO NOT ENGAGE THE FRONT AXLE ON DRY PAVEMENT! Engage the front axle only when needed. A wet road is not really a condition you need the front axle engaged. There is plenty of traction. Use only on snow and ice, and only when you really need it, not just because there is snow on the road.

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John Perry wrote:

your mech. is correct, thats normal with a 4 wheel drive on dry pavement.. you dont need all four wheels driving at the same time on a dry road.. the 4 wheels should only be locked in on off road or snow areas..... hope this helps.
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Thank you for your replies. Case closed.
John Perry

feel
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I disagree with things ive heard here...
First of all.. 4wd is not true locking front end.. if it were you wouldnt be able to steer at all.
The front end dif is slip and so is the rear.. as far as i know.
I engauge my 4wd on a dirt road like 2 times a month just to kep it lubed... otherwwise those parts will never get used and when i really need them they wont work
Kenny

appreciated.
wheel
turns
straight.
wheel
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The front end has an open differential in 99% of the 4x4 out there! None of the big three will put a locking differential in the front at the factory, I don't care what the salesmen might say, you may find some dealers who might do it for you?
The problem with the front end is that by turning the front tires you change the traction/resistance characteristics of either side of the differential. Remember in an open differential the side with the least resistance gets the power. So like with an open differential using the parking brake to apply equal resistance/traction to both sides you can send power to both sides.
By the way, exactly what parts do you think you are lubing twice a month?

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dunno anything that turns that wouldnt normally when not engauged... like the hubs etc... im sure there is something that moves when doesnt normally.... its good to make the gears mesh... in my own opinion
Ken

steering
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The hubs are not lubed by the gear oil, and they turn any time the wheels roll. Only the differential and carrier bearings ( typical differential, there are other types though ) which is in a bath of gear oil.

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ok so back to the original question... when in 4wd and at a low speed why do i hear a high pitched sound... if everything turns in there normally... something else must be turning or i would not hear the sound.
Also... the exterior hubs.. why dont i just kep them in the lock posision.. whats the difference of locked and auto?
They made this too confusing :)
I know it works.. i jujst want to uderstand how Kenny

four
minor
and
able to

the 4

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That's like asking "I have a stomach ach, what's wrong?". Could be gas, could be the flue, could be you ate too much.........so for the noise question, no real answer. As for the hub question, what is the year and model, there are quite a few configurations.

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interesting point.. i am not too concered about the noise.. however i do want to understand more about the way these hubs work>>>
2003 F250 4x4 hubs have "auto" and "lock" selection on the outside of the wheel. Please explain the difference.. the sales man explained it but i thought i got it and i didnt.
In auto i can switch from 2wed to 4wd inside... what is lock for .. he said for plowing .. i dont know why???
Thanks, Ken

be
the
the
taking
going
drive
engage
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The hubs on your truck can be applied by vacuum or by locking in manually. When you put the hubs in "auto" The module watches the speed sensors, when the speed sensors indicate a speed difference ( front vs. rear ) it assumes the rear wheel are spinning. It commands the solenoids that control vacuum to the hubs to energize and the hubs lock, your now in 4x4. If you have the hubs in "lock", your locked all the time. When plowing, you want it locked all the time, because you need 4x4 all the time.

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i still have the 2wd 4x4 high and 4x4 low switch in the truck.. it is not auto 4x4./... i still dont get it.
Ken

would
with
make
or
wheel
was
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Like I said in simple terms.
You have electronic shift on the fly. When you put the switch to 4X4 low or high with the hubs in auto, the module will engage the front axel when needed ( four wheel drive ONLY when needed ). When you put the hubs in "lock", they are locked ( you are in four wheel drive all the time ) and the auto function is by-passed.

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