Transmission Bucking Prior to Downshift

[Bronco Guy]

I tried searching for a similar issue, but didn't come up with anything. I installed some 33" tires on my 2000 V8 Explorer and now about the time the engine starts to lug down and before it downshifts, it bucks rather than just downshifting smoothly. If I turn off the overdrive, this seems to help for the Drive-Overdrive situation, but it does the same thing at lower speed shift points too. I still have the original 3.73 gears so I'm wondering if the computer is confused on when it should shift since the speedometer is off. I'm fairly sure it isn't the engine running rough since it runs smoothly at all other times other than when trying to decide on whether to downshift or not. I'm wondering if this is a common issue when putting on bigger tires and having the speedometer off. I'm wondering if correcting the gear ratio would solve it, correcting the speedometer ratio and maybe an aftermarket transmission controller, like the Baumann Quick 2 or 4 would help.

 

[MakinJeepsWeep!]

I dont really see how tire size change would effect it, it would be the same if you where pulling a trialer with the extra load, it should shift off throttle position and rpm not speed. I would make sure the shop that put the tires on didnt mess something up.