General 4WD Questions ('92 mainly)

Hi everybody,

I live in South California and we've been getting a lot of rain lately (at
least WE think it's a lot) so I've been driving through some deep mud
lately. When driving through the mud my Explorer (I have a '91 and my wife
drives a '92EB) sometimes the car goes sideways, especially if I'm going
uphill and have to give it some gas in a slippery area. It is my
understanding that when 4WD is engaged the rear tires turn faster than the
front tires. To me this would make the back end want to try and catch up
with the front end. I've never driven any other 4WD vehicles so what I'm
asking is would an all-time 4WD car/truck be less likely to go sideways, or
does it really matter? Aside from that the Explorers have come through
where just about everything else got stuck (except an F250 that was pulling
everyone out and some 'ol guy in a Plymouth Voyager of all things). Most
folks around here gave up and didn't go anywhere for several days and we
continued on with business as usual.

Also, if one of the auto-hubs on a '92 is bad will it make a clunking sound,
especially while turning? My wife said the car just plain wouldn't go any
more at one particularly slippery place but when I tried it I heard a clunk
and made it through no problem. If it's not the auto-hubs then is there a
common problem with the front differential or transfer case etc? I can see
the front drive shaft turning when 4WD is engaged so it looks like the
transfer case is OK. I put Warn manuals on my '91 but never could "see"
anything wrong with my auto-hubs but they definately didn't work.

Last one: on the '91-'94s does the differential slip or is it like a geared
shaft?

Thanks.

I believe the pre-95 Explorers had a "traditional" 4WD setup where the
transfer case locked the front and rear driveshafts when engaged and
automatic (sometimes replaced with manual) hubs on the front wheels allowed
power to be engaged. There may also have been some sort of front axle
disconnect tied in with the transfer case. In no case when in 4WD do the
rear wheels travel faster than the front unless something is wrong and you
do not have the front wheels engaged (that is to say, your 4WD is not
working). The hubs were known to wear out, so they may need replacing, and
if there is a front axle disconnect that may need to be checked as well.
Some checks you could make: do you hear the transfer case engage when
selecting 4WD? On a dry surface and at slow speeds, does the vehicle "bind
up" in 4WD during a turn (it should, which is why you shouldn't drive with
4WD engaged on dry surfaces)? On slippery surfaces do the front wheels spin
under acceleration the same as the rear wheels?

From your description of the clunking and driveshaft, sounds like the hubs
are bad in that vehicle. The front differential does allow slippage so if
one side is spinning the other will not turn.

=Vic=
Bear Gap, PA

"Ulysses" > wrote in message
...
> Hi everybody,
>
> I live in South California and we've been getting a lot of rain lately (at
> least WE think it's a lot) so I've been driving through some deep mud
> lately. When driving through the mud my Explorer (I have a '91 and my
wife
> drives a '92EB) sometimes the car goes sideways, especially if I'm going
> uphill and have to give it some gas in a slippery area. It is my
> understanding that when 4WD is engaged the rear tires turn faster than the
> front tires. To me this would make the back end want to try and catch up
> with the front end. I've never driven any other 4WD vehicles so what I'm
> asking is would an all-time 4WD car/truck be less likely to go sideways,
or
> does it really matter? Aside from that the Explorers have come through
> where just about everything else got stuck (except an F250 that was
pulling
> everyone out and some 'ol guy in a Plymouth Voyager of all things). Most
> folks around here gave up and didn't go anywhere for several days and we
> continued on with business as usual.
>
> Also, if one of the auto-hubs on a '92 is bad will it make a clunking
sound,
> especially while turning? My wife said the car just plain wouldn't go any
> more at one particularly slippery place but when I tried it I heard a
clunk
> and made it through no problem. If it's not the auto-hubs then is there a
> common problem with the front differential or transfer case etc? I can
see
> the front drive shaft turning when 4WD is engaged so it looks like the
> transfer case is OK. I put Warn manuals on my '91 but never could "see"
> anything wrong with my auto-hubs but they definately didn't work.
>
> Last one: on the '91-'94s does the differential slip or is it like a
geared
> shaft?
>
> Thanks.
>
>

Thanks. I guess I misunderstood something that I read a long time ago. I
thought that the gear ratio was different on the front as opposed to the
rear resulting in the wheels turning at different speeds.

I'm hoping it's just the autohubs that have gone bad finally. I put Warn
manuals on my '91 and have one possibly good autohub left over that I can
try and see if it clears up the "clunk" on the '92.

Just a reminder that you should NOT engage the 4WD on any surface that
does not allow some tire slip. You suggest that the rears drive at a
different speed. Not entirely accurate, BUT when you do turn, the
fronts need to turn faster that the rears, since they follow a larger
arc than the rears. With the transfer case locked in 4WD, turning will
cause the driveline to bind up as the front tries to turn faster than
the rear but can't. This shows up as clunking and feels like you have
less power. On a loose or slippery surface, no problem as the tires
will slip some to allow the difference in speed/distance travelled.
But on hard stuff, you really strain things, including the plastic
splines in he auto-hubs, when you use 4WD.

The failure mode on the early 4WD hubs is a grinding sound as they try
to engage but can't.

Hope this helps!

dr bob



Ulysses wrote:
> Thanks. I guess I misunderstood something that I read a long time
ago. I
> thought that the gear ratio was different on the front as opposed to
the
> rear resulting in the wheels turning at different speeds.
>
> I'm hoping it's just the autohubs that have gone bad finally. I put
Warn
> manuals on my '91 and have one possibly good autohub left over that I
can
> try and see if it clears up the "clunk" on the '92.

Well, I guess some dirt is slipperier than other dirt, but I'm getting the
clunk on fairly loose dirt where I'm not feeling any binding.

Thanks for the explanation about the tire-turning speeds. I'm not sure
where it came from but someone or something said the gear ratio was
different on the front. Maybe someone who wasn't real knowledgeable told me
that and it got stuck in my brain. So much for my theory about all tires
turning at the same rate keeping the car from going sideways. Now I know
why so many SUVs have those little propellers on the back. Sounds like a
rudder might be useful too for the driving I do (mud over 2 feet deep
sometimes). Is there a better tire I should be using for mud? I have
Michelins LTXs and they seem to be good overall in various conditions.
AAMOF There were people at the top of what we now call "Stuck Car Hill" that
were cheering when I actually made it without getting stuck, so maybe the
Michelins are pretty good after all. I tried BFG All Terrain/TAs on my
wife's '92 and we both thought they were not as good as the ol' recalled
Firestone Wilderness tires. They (BFGs) seemed to slide more on ice and mud
and were a real bitch to try to put chains on. They seemed to be good on
loose dirt though.

So, if the drivetrain is binding due to lack of slip does that mean the
front differential on the early Explorers does not slip? I thought (here I
go probably being wrong again) that if one side had traction and the other
didn't the one without traction would spin and the other would slip.

The binding in 4wd with a locked transfer case is due to the different
speeds between the front wheels and rear wheels in a turn, not a locked
differential (unless yours has been modified). The rear wheels make a
smaller circle when you turn, so they must go slower and if you are in 4wd
either a wheel has to slip somewhere or something has to break. You would
get the same effect even in a 2wd vehicle with a locked differential. I do
understand that some mud racers (off road only, of course) use different
gearing in the front and rear to keep the rear spinning for floatation or
something, but that is a specialty application. Newer Explorers use Control
Trac which, in auto mode, release the transfer case frequently so the bind
up doesn't occur, or use AWD which does not lock the front and rear axles
together but in effect uses a differential between front and rear (which
also means it doesn't supply as much traction in poor traction situations).

I personally don't think you can do better than the Michelin LTX series on
an Explorer. The M/S version is the one I prefer overall, having had both,
but the A/T version has a more aggressive tread pattern if you spend a
significant amount of time off road. In snow and typical muddy farm and
logging road use to repair radio repeaters I see no difference in traction
and the M/S versions are more pleasant on the highway.

=Vic=
Bear Gap, PA

Ulysses" > wrote in message
...
> Well, I guess some dirt is slipperier than other dirt, but I'm getting the
> clunk on fairly loose dirt where I'm not feeling any binding.
>
> Thanks for the explanation about the tire-turning speeds. I'm not sure
> where it came from but someone or something said the gear ratio was
> different on the front. Maybe someone who wasn't real knowledgeable told
> me
> that and it got stuck in my brain. So much for my theory about all tires
> turning at the same rate keeping the car from going sideways. Now I know
> why so many SUVs have those little propellers on the back. Sounds like a
> rudder might be useful too for the driving I do (mud over 2 feet deep
> sometimes). Is there a better tire I should be using for mud? I have
> Michelins LTXs and they seem to be good overall in various conditions.
> AAMOF There were people at the top of what we now call "Stuck Car Hill"
> that
> were cheering when I actually made it without getting stuck, so maybe the
> Michelins are pretty good after all. I tried BFG All Terrain/TAs on my
> wife's '92 and we both thought they were not as good as the ol' recalled
> Firestone Wilderness tires. They (BFGs) seemed to slide more on ice and
> mud
> and were a real bitch to try to put chains on. They seemed to be good on
> loose dirt though.
>
> So, if the drivetrain is binding due to lack of slip does that mean the
> front differential on the early Explorers does not slip? I thought (here
> I
> go probably being wrong again) that if one side had traction and the other
> didn't the one without traction would spin and the other would slip.
>
>

Just a general comment - I thought it was standard practice to cut the
front differential ring gear with one less tooth than the rear. This
causes the front tires to want to pull more (turn faster) than the rear
tires. The reason you want this to be the case is that it adds greatly to
the vehicle controlability on soft (dirt, mud, snow) surfaces. You want
the front end to pull you into a turn rather than allow the back enbd to
puch the front end into a plow.

My experience is limited to the Chrisler products and all I have heard
about the others. Local 4WD shops understand that the gear ratios are
slightly different front to back on all 4WD vehicles. Their repair
experience is high but their design experience is neglegable.

I'll emphasize as others have. If you engage 4WD on dry paved surface,
you will most assuredly burn something up very quickly. Bank on it.

Regarding AutoHubs - if you are not very technical, manual hubs are dirt
simple and will never mislead you. They are either engaged or not.
Either condition is very easy to verify.

I, on the other hand prefer AutoHubs. I think they are mechanically quite
sophisticated and very clever in design. Besides they are cute...
sometime troublesome but cute.

I probably confused things more than I helped. Sorry

G

"Professor3700" > wrote in message
lkaboutautos.com...
> Just a general comment - I thought it was standard practice to cut the
> front differential ring gear with one less tooth than the rear. This
> causes the front tires to want to pull more (turn faster) than the rear
> tires. The reason you want this to be the case is that it adds greatly to
> the vehicle controlability on soft (dirt, mud, snow) surfaces. You want
> the front end to pull you into a turn rather than allow the back enbd to
> puch the front end into a plow.

Professor,

Time to go back to school. The ring and pinion ratios are identical front
and rear. If you modify one, you must modify the other to match them. If
not, there would be big driveline problems.

-Fred W

"Professor3700" > wrote in message
lkaboutautos.com...
> Just a general comment - I thought it was standard practice to cut the
> front differential ring gear with one less tooth than the rear. This
> causes the front tires to want to pull more (turn faster) than the rear
> tires. The reason you want this to be the case is that it adds greatly to
> the vehicle controlability on soft (dirt, mud, snow) surfaces. You want
> the front end to pull you into a turn rather than allow the back enbd to
> puch the front end into a plow.

This was my understanding before I posted my question here. But it also
seems to me that by having the rear wheels turn a bit faster than the front
might be part of the problem I have going sideways in slippery mud. Of
course there are so many factors involved here that it might be hard to
determine if identical gear ratios would help.
>
>
> I'll emphasize as others have. If you engage 4WD on dry paved surface,
> you will most assuredly burn something up very quickly. Bank on it.

It seems that on the early Explorers it was the autohubs that burned first.

I mistakenly thought that the reason why there is binding on turns in 4WD on
non-slip surfaces was because the differential was not slipping on the wheel
inside the turn. I now (think) I understand that it is between the front
and rear wheels that causes the binding to occur. Right now I'm trying to
understand how I could have one autohub working effectively giving me 3
wheel drive and why is the wheel with the traction not slipping but the one
with the bad hub just sits there. It seems like with a bad hub neither
front wheel would turn.