Towing Four-Wheel-Drive Vehicles

By Edward D. Johnson

 

  I’m often asked why an owner’s manual allows towing a vehicle with all wheels on the ground without limits but restricts towing with one end lifted. It’s a logical question with simple answers. When a vehicle is towed with all wheels on the ground, the fluid level in the transmission and transfer case remains fairly level and moving parts are able to dip into the fluid to obtain lubrication and circulate the fluid. Some parts pick up fluid and throw it around and lubricate other moving parts. When one end of the vehicle is lifted, the fluid level shifts and parts are no longer able to reach the fluid.

  Manufacturers specify speed and distance restrictions based on whether the transmission is level or tilted. As a tow provider for a local transmission shop for over 30 years, I have seen transmissions and transfer cases that have been destroyed by bad towing. Among those are transmissions in which parts got so heated they would weld into one piece, A few years ago I was asked to examine a Ford T-Bird after a 70 mile front tow. The entire drive system broke. My examination determined that the transmission locked first, and then the driveshaft broke because the transmission would not allow it to turn, and the locked driveshaft then snapped the rear differential. The cost of repair was over $6,000.

   A lot of misconceptions about towing four-wheel-drive and all-wheel-drive vehicles circulate through the towing industry, and acting on the misinformation causes a lot of damage. Just because a four-wheel-drive system has a neutral position does not mean it is towable. On some vehicles, when the transfer case is shifted into neutral, transfer case parts are disconnected from the transmission but the front and rear wheels remain joined through the drive shafts in the transfer case and towing with any wheels on the ground will cause serious damage.

   In the 1970’s, many Chevrolet four-wheel-drive pickup trucks were designed to sling towed with the transfer case and transmission in neutral, but when wheel-lift trucks came along, those settings would not work. The truck would try to climb out of the wheel-lift. It was necessary to shift the transmission into neutral and the transfer case into “2Hi” in order to tow with a wheel-lift. Manufacturers called for Jeep CJs built from 1976-1986 to be towed from the rear with the manual hubs locked so front axle fluid would be circulating during the tow. Towing with the manual hubs unlocked did not circulate fluid and the front axle would overheat.

The rule: Never tow any vehicle on its drive wheels unless the manufacturer’s manual gives you the specifications.