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.
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.
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
I can't believe they actually inspected the truck! This is a very common 4X4
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.
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.
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.
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
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?
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
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.
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
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
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???
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.
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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