Deceleration Vibration

I started to get a slight Deceleration Vibration some where around 35 to 40 mph. I does it in drive and when I select 4 manual. I have a 2012 JK 2-DOOR -Auto Trans with 61000 miles. it does not do it all the time. It shifts fine other wise. The only thing is I put a new set of COOPER RUGGED TREK Tires and run 35PSI IN THEM. I thought about a Transmission Flush. Any other Ideas ??

 

Don't flush, replace filter and use correct fluid - not universal, not 1 style fits all,
not adding an additive to shop generic fluid, use correct fluid.

 

Vibration is caused by rotating mass. Worn suspension can make vibration worse, but shouldn't be causing it.
When you decelerate, weight is transferring to the front. Check for play in the front driveshaft cv joints.
If the vibration is coming through the steering wheel, check front axle u joints and wheel bearings.
If vibration didn't start till after you put on the Cooper tires, I wouldn't completely rule them out. Might try rotating front to back and see if anything changes.
Let us know what you find.

 

I had a rock wedged between the exhaust pipe and the cross member.