r.p.m rev

[outthere]

Hi ya'll, just bought my first mh. 2000 allergo workhorse 7.4 with 43,000 mi. Belonged to a retired preacher that loved to keep ALL service records. I do most of my work myself, 4-wheelers, My tractors, kubota 1991, Gravely7.6 walk behind mower(1971) and everything else that has a motor on it. My question is when i go down the road the rpm jumps around 100 to 200 more than normal (1,500 rpm), every 2-3 miles even on level road going 50 mph with cruise/ without/ on o.d or just in drive. do i have a vacuum leak? computer problems? have plenty of power when i apply, so i dont think it's tranny slipping. any ideas? thanks in advance, and pics coming soon.....

[Nick-B]

My first thought is the torque converter is not staying in full lockup and is randomly unlocking. One of the items that triggers it to unlock is the brake light switch. It could be that the switch is flaky or set "on edge" so that any jiggle on the brake pedal (bump in the road) activates the brake lights and unlocks the converter.