88 Silverado one front and one rear wheel drive while in 4 Hi range? Why???

I have an old 88 with 160000 mi and it has a strange behavior lately.
I got it stuck and found that only the drivers front and pax rear
wheels are driving. I had the offending front axle just replaced and
it did it before that so it sort of eliminates that possibility. The
fluids seem to be ok as well. I put it in LO range and it seemd to
drive right out of the rut I was caught in, does that make any sense?
Any ideas what to look for here?

Sounds like perfectly normal operation for a "4x4" with "open"
differentials. The "open" differentials are doing what they are designed
to do and letting one wheel turn faster than the other.

With a part time 4 wheel drive vehicle and "open" differentials in 2WD
you really have one wheel drive (the one with the least traction) on the
rear axle and no power to the front axle. When you put it in 4WD you
really get two wheel drive, the wheel with the least traction in front
and the wheel with the least traction in the rear.

When you went to 4WD-Lo it didn't do anything to the differentials, but
the much lower gearing probably helped to keep the wheels from breaking
traction so you were able to move.

This is why they make limited slip and locker type differentials for
both front and rear axles. If you have a limited slip differential in
the rear you get something closer to 2WD in 2WD and 3WD when in 4WD. If
you have one in front as well you actually get 4WD in 4WD.

Of course there are tradeoffs with limited slips and lockers. Rear
lockers can be rather harsh on sharp turns when conditions are not
slippery. Rear limited slips are a bit milder.

A limited slip or locker in the front can be rather dangerous if you are
not well aware of it's characteristics. A front LS or locker will
significantly affect steering on turns and the sharper the turn the
worse it can be. This is one of the reasons they make selectable lockers
which operate just like a normal "open" differential until you
specifically engage them.

Pete C.



Drizler wrote:
>
> I have an old 88 with 160000 mi and it has a strange behavior lately.
> I got it stuck and found that only the drivers front and pax rear
> wheels are driving. I had the offending front axle just replaced and
> it did it before that so it sort of eliminates that possibility. The
> fluids seem to be ok as well. I put it in LO range and it seemd to
> drive right out of the rut I was caught in, does that make any sense?
> Any ideas what to look for here?

In article <[email protected]>,
[email protected] says...
> I have an old 88 with 160000 mi and it has a strange behavior lately.
> I got it stuck and found that only the drivers front and pax rear
> wheels are driving. I had the offending front axle just replaced and
> it did it before that so it sort of eliminates that possibility. The
> fluids seem to be ok as well. I put it in LO range and it seemd to
> drive right out of the rut I was caught in, does that make any sense?
> Any ideas what to look for here?
>

The next time that happens, if the wheels still sping in 4lo, ride the
brakes as you give it gas and you should get some power to the non-
spinning wheels.
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