Is it posible for the 4th gear lock up
( overdrive) in a automatic to engage and disengage rapidly? I have a saturn 02 sc1 67k and in 4th gear when at a steady throttle in the 45 to 52 mhp range I can hear a hum hum hum sound. Get above or below that speed range and I can hear the “steady” hum of the engine that sounds normal. No codes, no engine misfire,car goes down the road smooth when this occurs. Pop it into neutral and the sound goes away. Any ideas what it couuld be? Torque converter? Bearing? Over drive rapidly kicking in and out? Please help, Im desperate… thanks
If the torque converter is falling in and out of lockup, you are going to notice a 200-400 RPM increase and decrease. One of the most common things that causes this problem is a faulty TPS (Throttle Position Sensor) I would scan it for codes. If no codes are present, I would then let a transmission shop scan it while driving it, they can then monitor the TPS by itself and see whether it is the culprit.
transman