Since I have put 35 x12.5 x18 tires,3"Airraid Airflow system on I have noticed that around 63 to 65 miles a hour in overdrive my truck seems to want to shift down not up and seems to scream at me. If I let up on the gas an back down to 60 all is fine if I give it gas it wants to do it again, if I gas it it works its way thru it. It will run around 1800 or so RPM's If I am out of overdrive it doesn't seem to do it., but it jumps up to around 2200 RPMs I assume it has to do with the torque converter being confussed, mostly from the tire size causing the speedometer to be off and throwing the computer off wack. I attend to put 4:56's in it front and rear. I assume that will clear up some of this since I will bring things back closer to stock.
My question is this something a tuner will correct. I plan to go with Troyer's custom tune. I know this can't be good on the engine. My concerns is will this be corrected with a tuner. Can I also get some feed back if this problem is being caused by what I think it is> Thanks

 

YA, me thinks you need a tuned chip with all the corrections.
The PCM is programmed with the original factory eqippage; you upset it a bunch.

 

You should hurry up and get the gears changed (4.56 or 4.88) before you cause major damage to the transmission and engine.

 

Hi WifesF150,

Yes, with those huge tires you've thrown off the system, so the PCM & transmission do not know the correct speed the vehicle is traveling - and thus cannot accurately achieve appropriate shift point & TQ lock/unlock timing in certain types of driving situations.

You have also dramatically reduced torque multiplication, which in and of itself, will cause more TQ unlock/lock cycles and downshifting as well.

For now, I'd suggest having us take care of the speedo calibration issue so that the tranny will not be "confused" any more, and that will help a good deal - and then when you can afford it, get the gears in there (I suggest 4.56's with 35's) to restore the basic torque multiplication so you can really enjoy that vehicle to the fullest.

Please feel free to give us call to go over this in more detail, OK?

Hang in there, this is fixable!