2004 EB Vibrations when deaccelerating

[BREXP04]

New to the "Serious Explorations" and looking for some help with an intermittent vibration. I have a 2004 EB with 85k, and when I get up to cruising speed and then slow down I get a vibration, like when your running over rumble strips. It's not a continuous vibe and it does not matter if it's in gear or in neutral. When I bought it 2 yrs. ago it had worn tires on the front, and I have read many forums about mismatched tires on a 4WD automatic. Recently, I had a Transmission tech test drive it and he felt it was trying to engage into 4WD, but he didn't have time to get to it so I took it home and removed the front drive shaft and the vibration went away. My next plan of attack is to put all new tires on and go from there, but if it is in the TC what is the best way to test it w/o taking it out? :scratch:

 

[jrford]

Do the Tires first, most likely the cause if different sizes. Another test is to pull the plug/fuse on the 4x4 with the front shaft in and see if it repeats. If so I'd also check the xfr output shaft for play there should be no up/down or side/side play, also the pinion shaft on the diff. The shaft should rotate some, 1/16th that OK.

 

[BREXP04]

The tires are the same size, but one set is worn a little more than the other. I just don't understand how the 4WD auto can be so sensitive that it causes damage to the TC/drivetrain because of worn tires.
Now the 2004 has several fuses/relays, #12 fuse 4x4 switch under the dash, #17 Two speed 4x4 relay coils Power Dist. Box, #18 PCM w/two speed 4x4 clutch Power Dist. Box, so to test which one do I pull?
Thank you for your response!