OT GearVendors underdrive/overdrive

It wasn't cheap, I think it was $2600 installed. If I remember right it was a .87 OD and effectively turned the 4.10 to a 3.20 and I saw an 18% rise in fuel economy.

If I had it to do over again I think I would go with the Liberty OD box. It was set up to go between the transmission and transfer case to be able to use all the gears in both 2x4 and 4x4 modes. It would be more expensive requiring more mods but I think it would be more versitile.

On my '98 F-150 with manual transmission, the factory 3.08 gears left it lifeless and limited to 2200 pounds trailer towing. I considered such an underdrive, but its price was too high. I paid a local hot rod shop to put in 4.10 gears in the drive axle that increase the GCWR from 6500 to 9900 pounds and I rate the truck at 4700 pounds trailer towing rating now. I've loaded it to 6000 pounds in a wagon of beans and had no problems hauling that to the elevator and up the slopes to the scale and leg.

The engine is a 4.6 L V-8 and with its HP peak at 4700 RPM the factory gearing in overdrive put it down around 2200 RPM like a diesel and it hasn't guts at low speed. Its a high speed engine.

And though I was prepared to accept a loss of gas mileage it averaged 16 mpg unloaded before and still gets 16 mpg after unless I run it in the low 80 mph for hundreds of miles. Last weekend I did 390 miles with a 3000 trailer on its tail on 25 gallons of gas.

Yup I'll probably wear the engine out faster by running it faster but it sure does have great throttle response and gets off a line well.

Gerald J.