Hey everyone, I have a 98 navigator with 4x4. The problem im having is when im in (4hi), its hard to accelerate when im turning. Like pulling into a parking spot. It felt like I had a flat tire. It also makes a slight humming noise when Im going down the road at normal speeds. It all goes away when I go into (2hi). Ive been using (4hi) an awful lot. Is that bad? Should I use (A4WD)? I live in the northeast and we were just hit with a pretty bad snow and ice storm. Any help is greatly appreciated. God Bless!!

 

You have to understand that the front wheels are locked togather in 4H.
When you corner, one wheel want to go faster and one slower. This causes a bind to take place trying to turn on any dry hi grip surface.
Some of the rumble in straight away driving is the difference in tire diameters between front and rear not turning at the same rate. This creates a fast correction of sorts that is the rumble you feel and hear.
Actually, turning is trying to do the same thing.
You have a selector switch, turn it off before making sharp turn on dry pavement.

 

Hey, thanks a lot. That makes so much sense! I never would have thought of that. This is also my first 4WD, so I really dont know all the rules to it. Thanks so much for your input, hopefully I can assist you in the future.

 

They are? To my knowledge the front is just an open differential, meaning the tires can turn independent of each other.

Why would the front and rear tires have different diameters?

Am I missing something?

What I think you may be trying to say is that the transfer case is not a differential. It divides power 50/50. When you turn, the front axle turns at a different rate than the rear axle. If the transfer case did act as a differential, it would allow the axles to turn at different speeds, making 4wd useless. You would have one axle turning while the other did little or nothing, much in the same way that an open differential only spins one tire. Your 4wd could easily become one-wheel-wonder. However, since the transfer case is pretty much a spool, binding occurs when the front and rear axles (try to) turn at different speeds. When turning in 4wd, it is perfectly normal for one or more tires to skip across the ground. If you have good traction, it will also make it difficult to turn or accelerate while turning. That is why you shouldn't use 4wd while on hard dry surfaces.

 

Turn the switch to A4WD and leave it there. The transfer case will do all the work for you. In all wheel drive(A4WD) the transfer case uses electro magnetic clutches to differentiate between the different speeds of the front wheels and the rear. In 4Ho or 4Lo there is no differentiation it is a solid mechanical link. Because of this solid link and the fact that the front wheels turn at a different speed on turns than the rear, something has to slip. The link in the transfer case will not slip in 4Hi or Lo and if traction is very good, like was mentioned on dry surfaces, the wheels will slip. That is called binding. The drive line gets very tight and acceleration is difficult. Doing this over time will cause premature wear on the drive line components.

JMC