Sometimes it would shift to overdrive then sometimes it wouldn't but now it isn't going into overdrive at all
My car has 152000 miles.
My car has an automatic transmission.
The problem can be as simple as the transmission fluid and level. Make sure the level and fluid condition (should be a reddish color) are as they should be. If the fluid is not good, there can be mechanical issues with the transmission. As components within the transmission wear (clutch packs,etc), the worn material wind up in the pan and floats around the transmission with the fluid causing more wear. Poor fluid condition can cause the transmission to run hotter and accelerate problems. The best route would be to find a local transmission specialist to have the transmission inspected.
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