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4 Wheel Drive/SUVs/4 wheel drive at speeds over 30 mph

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Expert: - 10/31/2005


Question
Mr. Brandt, you may not be the one to answer this question but I'll give it a shot.I recently bought a 2005 Hyundai tuscon 4 wheel drive SUV and so far I love it. But I have a question about the 4 wheel drive. The dealer told me that the four wheel drive only works at speeds 20 mph or less. The owner's manual coincides with this and goes on to say that at 30 mph the 4 WD is at 50% effective and at 40mph - no longer effective. The dealer tells me this is true with all 4WD vehicles. I looked in the owners manual of my husband's 4x4 dodge ram and it doesn't say anything of the sort. Is this true that 4WD only is effective at 20 mph or so? Thanks for any info you can give me.


Answer
Grace,

First of all, it sounds like the Hyundai does not have true 4-wheel drive, but an all wheel drive, or a full-time 4-wheel drive system of some type.  In this case, you probably do not have a transfer case.  this indicates that the all wheel, or 4-wheel drive in this vehicle is intended to work all the time with some speed limitations.  

Your system sounds more like a 4-wheel assist, or traction control than a 4-wheel drive.  I'm sure that the dealer is correct in the operation of your car, but he doesn't know very much about a true 4WD vehicle.

Any true 4-wheel drive vehicle, such as your Dodge, should not be operated on any hard surface such as asphalt in 4-wheel drive, unless you are in snow or ice (possibly heavy mud.)  This is why they have a transfer case, and can be shifted in and out of 4-wheel drive.  A true 4WD vehicle, when shifted into 4WD is driving both the front end, and the rear end at the same time regardless of the speed you are going.  Some 4WD vehicles, such as my Grand Cherokee, have an additional set of gears in the transfer case that allows for 4WD operation on hard surfaces.  This is called "full-time."  Vehicles that have this, also have a part time, or locked position for off-road, or snow driving.

I hope this will give you a small understanding of how 4-wheel drive works.

Carl

4 Wheel Drive/SUVs

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Carl Brandt

Expertise

Will discuss suspensions, lifts, lockers along with tire suggestions. Trail ratings and possible requirements needed for specific type of trails. Safety equipment and what you should carry with you. Certified off-road instructor. I am not a mechanic, and 4-Wheeling is a hobby, so if I can't answer a technical question it is due to my mechanical knowledge being related to vehicles that I have owned, or have worked on. I do not have manuals on all vehicles.

Experience

40 plus years of 4 wheeling in a variety of vehicles. At the present time, my major off-road rig is a 94 Jeep Wrangler with a spring over and a 1 1/2" suspension lift. This gives me a total lift of 7" or so. I have lockers front and rear. I have removed the track bars, and sway bar for maximum articulation. I am running a stock 2.5 ltr 4 cylinder with a Jacobs ignition along with a cold air high flow filter. It has 4.56:1 gears with a Dodge NV4500 transmission along with a 3.8:1 Atlas II transfer case. This gives me a final ratio of 105:1 in low gear/low range. Other vehicles I own, are a 96 Ford F-250 with a 6" lift, posi rear end, 36" Hummer tires, 5 speed with a fuel injected 460 ci engine, an 87 Samurai with an 8" lift, Ford 9" rear end with a spool, Chevy Dana 44 front end with an electric locker, 5.88 gears, 16% reduction in high range and a 6.5:1 low range with 35" Baja Claws, and a stock 2003 Grand Cherokee Overland. Trails I have run are the Rubicon (10 times), Dusey Ershim, Fordyce Creek trail, McGrew trail, several trails in Moab, Utah along with local monthly runs.

Organizations
Lost Coast 4x4's Cal 4-Wheel Corva UFWDA Blue Ribbon Coalition

Education/Credentials
Certified off-road instructor - Certificates in engineering/electronics

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