Re: Power tuner for 2010?
I dont think your problem will be solved by a Power Tuner. You really messed with the gearing when you went to the big tires and you will be money ahead by changing your gearing. Your O/D became almost useless and your first gear became too tall when you went to those tires. This is causing your torque converter to compensate by slipping. They are meant to do this, but your set up is working it way too hard this will cause the fluid to heat up and eventually burn causing premature transmission failiure.
Most stock vans come with 225/75 16 tires and 3.7 rear end, it must be the best ballance between power and economy. As an option they offer 4.1 for power and 3.55 for economy. Putting 33" tires will make it as though you went to a 3.28 rear end. Ford does not offer that ratio, and for good reason. It will make your engine and trans work way too hard. I think the highest/ fastest ratio they offer is 3.55. The difference seems small, but you need to multiply tire revolutions per mile by the rear end ratio to get the engine RPM at 60 MPH in direct (or multiply by your O/D ratio, probably .71? ) to get a true scence of the impact of big tires on engine RPM and performance.
"there is neither science nor fact prevailing here" - vlamgat