- Joined
- Aug 3, 2010
- Posts
- 30,830
- Reaction score
- 29,502
- Location
- Usually not in Ohio
- First Name
- Andy
- Truck Year
- '77, '78, '79, '84, '88
- Truck Model
- K5 thru K30
- Engine Size
- 350-454
If you are cruising down the highway and can tap the brakes just barely enough to light the brake lights, and the RPM's increase then the lockup is working. The factory engineered it to engage at other speeds too, but steady speeds in OD is the only time you need it, and also the only time it's beneficial to mileage.