Shudder when turning

Diagnose and fix shudder when turning condition

A shudder when turning condition or a shudder on acceleration, shudder on deceleration, or shudder or binding on slow turns on a four wheel drive vehicle 4WD can be caused by many things. However, the most common cause is uneven tire wear. Ford, for example has issued a service bulletin #08-21-11 to address these shudder when turning complaints on their 4WD F-150 vehicles. The bulletin applies to the following vehicles

1997-2008 Expedition, Explorer
2006-08 F-150
2007-08 Explorer Sport Trac

Lincoln
1998-2008 Navigator
2003-05 Aviator

Mercury
2005-08 Mountaineer

But uneven tire wear can also cause shudder when turning, shudder on acceleration, shudder on deceleration, or shudder or binding on slow turns on many other vehicles

In vehicles equipped with 4WD and some type of traction control, uneven tire wear can cause the system to shudder when turning, shudder on deceleration, or shudder or binding on slow turns. To diagnose the problem, first check the tires to ensure they’re all the same size and the size is what’s recommended on the tire placard located on the driver’s door pillar.

Check tire pressure

Refer to the placard on the driver’s door pillar for the recommended tire pressure and check the inflation of all four tires using a reliable tire pressure gauge. I recommend using a digital tire pressure gauge instead of a less accurate mechanical gauge.  Do NOT inflate the tires to the  pressure listed on the sidewall of the tire. That pressure is the MAXIMUM pressure allowed, not the recommended pressure.

Disconnect the transfer case wiring

To determine whether the problem is in the transfer case or due to uneven tire wear, disconnect the wiring going to the transfer case. Then take the vehicle for a test drive under the same driving conditions. If you still notice a shudder when turning, shudder on deceleration, or shudder or binding on slow turns, proceed to the next step.

Measure the circumference of each tire

Using a flexible tailor’s tape (not a retractable steel tape), wrap the tape around the circumference of each tire and record the measurements. Then calculate the averages according to this formula

Left front circumference plus right front circumference ÷ 2 to get average circumference
Left rear circumference plus right rear circumference ÷ 2 to get average circumference

If the average circumference between the front or rear side-to-side or the average circumference between the front to back is greater than ½” the uneven tire wear is the cause of the shudder when turning, shudder on deceleration, or shudder or binding on slow turns. The average circumference must be less than ½”. If it’s greater than ½” you must purchase new tires or replace the tire(s) with the greatest wear and have them shaved down to match the circumference of the remaining tires.

©, 2015 Rick Muscoplat