03 explorer bucking in auto 4x4

[nitrousbandit1]

03 explorer. 100k miles. bucks in between 2 hi and 4 hi i think. if i put the truck in 4x4 high using the switch the bucking stops. if i disconnect the trasfercase the bucking stops, ive searched this site about 50 times and hanvt found MY answer. either gem module or 4x4 control module. i can not locate the gem module but i have located the 4x4 control module.

annnnnnnd go

dave in chadds ford

 

[nitrousbandit1]

if the 4 tires are dif diameters it will throw off the auto 4x4. called ford dealer asked a few questions and thats why they told me. put a chalk line on all 4 tires in the same position, say 6 oclock. drive 40 feet. recheck the marks. if they are way off the tires are dif diameters. thats how mine was. drove 40 feet back tires and front tires where off by about 10 inches. both tires where 255-70-16s. but dif makes.