I have a 2001 ram 1500 4 wheel drive with an automatic transmission and when the truck is empty and I am driving on the freeway at 60 to 80 and I hit a bump the engine revs a little, it does this more when the cruise control on. The fluid level is good and it is only when the truck is in overdrive. I drive from Reno to Sacramento a lot and it seems to do it for the most part when I am in Sac. Hardly ever when I am in Reno. I am wondering if it is the altitude. I thought it was a tranny slip but when I am towing or have a load in the truck it is fine and does not act like it is slipping. It has a small lift and I found out that the other owner only used it to tow a trailer. Is this normal for it to do this when empty or is the transmission starting to go..

Does it just jump a couple hundred rpms? If so the TPS (throttle position sensor) could be bad or dirty. My '00 V8 Dakota did that also, I cleaned the sensor and it stopped.

if tps is not the cause of problem check your trailer light wireing over becuase your brake lights control that wonderful thing called a lock up torque converter. if there is a short in the wireing and you go over a bump it could be feasible for the lock up to come off which will cause a small change in rpm about 200-300