4 Wheel Drive/SUVs/AWD and tires

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Expert: - 10/13/2004


Question
I purchased a used '94 Aerostar E-AWD. I know this is not even close to an off-road vehicle, but as  i have never owned any AWD/4WD vehicle before any advice will help. The AWD was disconected (unplugged at transfer case)at purchase. After plugging it in everything seemed fine until 15 minutes at highway speed. Vehicle started a pretty severe vibration, almost like hitting grooved pavement. Stopped after 5 seconds. When it stopped it felt sort of like there was a torqueing tension released from the frame. I could actually feel a kick from the right side of my seat. This repeated again after 2 or 3 more miles until I exited expressway and unplugged TC again. The vehicle has mis-matched tires -205/75/14 in front and 195/75/14 in rear. Could this be the cause?  

Answer
Paul,

In any AWD, or 4-Wheel drive, it's extremely important that the tires be a matched set.  If they are not, you will be putting unequal torque on the transfer case.  This can put the transfer case in a bind, and tear up the internal components.  I would suggest that you have the transfer case checked out at a reputable shop, preferably one that specializes in 4-Wheel drives.  I'm not sure why the AWD was disconnected, but in some situations, that can be hard on the TC.

In any case, my suggestion, would be to install a set of matched tires, and keep the AWD hooked up.

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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