Too high rpm - overdrive? Keisler?

I can tell you i have 3, and none are newer than 14 years, the one in my truck is used the most and over 20 yrs old, with the most mileage and used for the horrible 3/4 split, and doubles as a od for pulling, that one paid for itself in gas savings in less than a year, over 20 something years ago, when gas was far from $3 and $4 a gallon never did anything but change the oil.

I have installed and sold lots of them, never one issue with any customers units.

The best product i sell that isn't mine.