Re: [A/S] Ford 2004-2005- Locking 4 WD

[Rick Kunath <k9ao@xxxxxxxxxxx>]

>  I learned very
> quickly, after coming to rest in several ditches, that a vehicle with the
> ability to "spin all 4 wheels under load" was a different beast to drive.

I suspect that is why the big-3 stopped pushing limited-slip differentials 
back a few decades ago, and make them optional. There were a lot of folks 
punching the accelerator around a corner and kissing mailboxes in the early 
days, not realizing that the vehicle would immediately donut on them.

> I 
> had 4 - 7.50 X 16 studded tires on the Blazer in the winter, which made it
> an awesome machine for ice covered roads, and pushing 3' deep snow. The
> problem was caused by the fact that most of us are use to our vehicle
> having at least one wheel that does not loose traction, and thus "anchors
> the vehicle on a side to side direction. When all 4 wheels loose traction
> under load, you are no longer in control of your direction of travel. 

That's why I haven't installed front locking in any of my on-road vehicles, 
though out in the extreme country of the southwest slickrock, you're going 
nowhere without locking front and rear. I prefer dual air-lockers under those 
conditions.

With the gear type locker in the rear and an open differential in the front, I 
don't experience any more issues than your typical front wheel drive vehicle 
does, even in extreme snowfalls and icing. I used to live up in the Upper 
Peninsula of Michigan, and lived for 10 years. 300 inches of annual snowfall 
was not that unusual.  We'd haul trailers into some ungodly places during 
deer season (snow and all.) The gear-type locker in the rear and open in the 
front seemed to be a pretty good setup for mostly on-road use. But, as you 
mentioned (and I forgot to mention), with any locker/limited-slip setup you 
need to remember that you have it, especially when negotiating turns and 
corners at high speeds. If you don't you run the risk of losing rear (or 
front if you've got a locker there) traction and seeing vehicle movement. 
It's not a big thing once you know it's there, but you do need to be aware of 
it. Front wheel drive vehicles see this on a back-off of gas during really 
slick conditions and loss of front steering control can happen, so do 4wd 
vehicles, even with open differentials. The answer if you're going straight 
and not turning is to gas it momentarily to regain control, and steer in the 
direction you want to go. This happens a lot off-road on sandy downhill runs. 
Toyota has actually built some dynamic chassis controls into the 2005 4wd 
vehicles to help manage this for drivers. 

The extra thought process is something to think about. 

Remember that if you've got a 4wd vehicle with open differentials, you really 
have a 2wd vehicle (and a 2wd vehicle is really a 1wd vehicle.) Going 
forward, if the left front and the right rear wheel of  4wd lose traction, 
you're stuck. In reverse the opposite wheels apply. With limited-slip or a 
locker in the rear, you wind up with 3wd. It can make a bug difference in 
poor traction conditions. But, like any technology, you have to know how to 
use it.

I prefer it, but that's my opinion, and I know how to handle the vehicle with 
it. If you get aggressive around a corner on ice, you are probably going to 
spin, but you probably would anyway. If you're pulling into a site and get 
wheel spin, you already have a problem. If you're on a side hill, you've got 
a bigger problem. 

This has been a really informative discussion... 

And, as another thought that was mentioned up a few threads, air-lockers might 
be another solution for some folks. I might give that a good long look this 
spring when I replace the tow vehicle. An air-locker is an open differential 
when not locked, and locks tight like a Detroit Locker when manually engaged. 
When unlocked, you've got your typical open differential 4wd (really 2wd) 
with characteristics as I described back a few paragraphs. The disadvantage 
of a true locker is that you lose directional control when locked. Turning 
and cornering are very difficult. With a gear-type locker, cornering is 
buttery smooth, you don't get the shakes and jerks of a full-locker. 

Hopefully there has been enough discussion on the various aspects of 
limited-slip and lockers to help anyone make an informed decision as to 
whether for them, it would be an advantage or a liability.

Rick Kunath
WBCCI #3060