2001 Pontiac Montana 6 cyl Front Wheel Drive Automatic 127000 miles
Our van has started slipping in first gear. It doesn't do it at first, but when we get to the third intersection leaving our neighborhood. (There is a very slight incline at that intersection.) Then last weekend after driving for about a half an hour, I heard a whinning. I looked at the gauges and realized by the tach, the motor was running too hard to be in overdrive. I slipped it into 3rd. The noise went away and the RPMs stayed the same.
The fluid always checks fine. Thin, light red, clean looking and no burnt smell.
If slippage is caused by pressure loss, or clutch slippage, there is going to be tell tale signs in the fluid(color, odor). Mechanical portions of the transmission(hard parts) are almost never going to have slippage as a symptom. With a failure of a hard part, you are either going to have no movement, or significant noise. What you are describing may be symptomatic of a torque converter, but that is not necessarily going to be gear specific, since it is doing the same thing in all gears. The exception to this is higher gears, and torque converter clutch lockup. This should happen in third and fourth gear, in excess of 40 mph is when it applies.