Auto or manual?
Man: oil on the clutch or bad/worn pressure plate,
Auto: Low ATF fluid. Incorrect voltages due to bad alternator.
check your transmission fluid, if it is low it will slip
does the speedometer effect the transmission
overheating of the fluid. This causes the transmission to slip. Slipping causes damage as friction material wears out quickly and even more overheating. This eventually causes failure.
check the fluid levels. that's the only thing I can think of.
Low transmission fluid will cause this and also weak bands inside the transmission can cause this.
I drove my 1995 Saturn sl2 until it had 263,000 miles on it. At that time, the transmission started to slip. I then gave it to a friend, to buy a newer Saturn sl1.
You might need transmission fluid !?!?
a blown transmission
Your transmission might slip on your ML320 because the transmission fluid is low or because the transmission is damaged. The most common cause of transmission slip is wearing of the transmission.
Try to replace the oil filter if the transmission is not engaging when it's cold.
The bands may be weak, it may be low on fluid.
bad linkage in shifting cable