I recently installed a Volant CAI and Borla exhaust system. Since then, I've noticed that when I am going down a hill and take my fooy off the gas, the transmission will downshift out of overdrive. It shifts back after completing the downhill section. On the Volant unit, one of the vacuum hoses does not fit very tight and I had to modify the MAS hole where it attatches to the CAI. I guess my question is, can a dirty MAS or a vacuum leak or an air leak where the MAS attaches to the CAI cause this behavior or should I be going to a transmission shop? Any thoughts will be appreciated. I suppose I could put the old air intake back and see if there's any difference but I thought i would ask here first. Thanks to everyone in advance.

Where does it go when it shifts out of overdrive? Neutral? 4th/3rd? The 4th Gens have shift logic programming that will downshift to apply engine braking when going down hill. Could that be what you're experiencing? I doubt that it actually shifts into neutral, but when not needing gas/braking to control speed, I've noticed the 4R seems to have less transmission drag than most automatics I've driven when no throttle coasting. Possibly this behavior was there all along and you're just being a bit more sensitive since you just made some changes.

Oh, yeah...where did you find a hill in Florida?

-Brent

You are correct regarding the downshift when going down the hill. I guess I just hadn't noticed it before now. It does seem to take it's time shifting back into overdrive, however. Does the mass airflow sensor have anything to do with the shift points? BTW, Tallahassee has PLENTY of hills. Thanks.