I recieved a underdrive pulley from underdog peformance for christmas and i am very happy with the performance and mpg increase. All i have is the underdrive pulley no other pulleys.
*I am also running 31x10.5" tires with 3.73 gear ration so rpms may very from truck to truck*
I have gone threw 3* tanks with the new UD pulley and have noticed a 1.2 mpg increase. The truck also feels much smoother when shifting with the UD pulley!
It gives the truck much more acceleration from looking at my rpms and speedometer and also my "butt dyno" can feel it. Before i had the UD pulley i would keep my rpms under 2700 and with an automatic tranny, so i was pretty slow with accelerating. If i am accelerating at 2700 with the UD pulley it speeds up much quicker at the same rpms. So with the quicker acceleration i just get the truck up to 2400-2500 rpms so i actually speed up the same but i am in lower rpms resulting in an increase of mpgs.
While driving down the road the truck stays at lower rpms which results in better fuel economy. Goin a steady 40 mph down a road with cruise control on, without the UD pulley it would be at 2000 rpms. When i got the UD pulley on, going 40 mph with CC on now the rpms are 1800-1900 which is another reason i get better fuel economy.
I am very happy with my UD pulley and would suggest this product to anyone with a ranger. If you are lookin for better performance, the UD gives you that. If you are looking to get more mpg, the UD gives you that.
Here are a couple pictures with the UD pulley compared to my stock pulley and also with the UD pulley on the truck: