thump on decel

[yellowstx]

I have an 02 auto 4wd, my front tires were BALD and the rears had about 1/2 tread cause I replaced them a year and 1/2 ago. so I put 2 new tires on the rear and moved the old rears to the front (all same size and make). I now have a thump or bucking on decel from about 55 down to 20 or so. If I hit the 4w high it stops immediately, I had this problem once before but when I changed the rear brakes and rotors It seamed to go away. The difference in tread amount is still about the same front to back as it was before also

 

[IZwack]

Sounds like the different tire diameter is kicking 4wd on

 

[jwright4]

disconnect the 4x4 control module (behind the glove box) and see if it continues. my 03 is doing the same exact thing. i know that the 4x4 control module is bad because i was having a problem with it last yr when i would accel. did not get around to replacing it yet, but this yr its doing the "thumping" on decel but as soon as i hit the 4x4 it stops. so i'm sure it's the module. hope that helps