No Overdrive

2001 Impala LS 3.8 ....I have a similar problem with overdrive. The strange thing is, if I start off from a dead stop and accelerate gradually at resedential speed, the tranny will shift normally into 4th at about 35-40 mph. If I continue to accelerate, it will stay in 4th until appx 50mph or 2K on the tach at which point it suddenly kicks up to 2200 and increases with speed from there. It's turning close to 3000 at 70mph. At freeway speed while turning 3000 if I let off and coast, the tach drops to 900 just like at idle. It's like I put the thing in neutral, and it seems to be freewheeling. Mechanic says it needs a rebuild to the tune of $3K. Why does it go into 4th but not stay in 4th?... Is there something simple here, or is it really a $3K issue? It's been flushed; filters changed etc... No Joy. I have 111,000 miles on it.

Thanks

Mike

Do you know if there was any transmission codes?What are they saying is actualy wrong with it.

No SES light & no codes.

It needs to be scanned with a trans function scanner to look at solenoid operation and slippage error/codes, no other way to accurately diagnose this.

Do you have a 2nd gear start switch on this car? I have found that all cars, that have a 2nd gear start switch, will have a temp sensor in the transmission. I bypassed the sensor with a 3 ohm resistor installed in between the 2 wires coming out of the transmission. The transmission was not hot, it was a bad sensor. I simply cut the correct wires and installed a resistor and now the computer always sees 85 degrees on the trans temp. It works great.

Some people are saying that I should not have done this and that I should not operate it like that. I disagree. Most 4T60-E transmissions do not have the temp sensor. It is not hurting a thing and the transmission is working great.

The temp sensor was saying that the transmission was hot. This information is used by the computer to tell the transmission to shift to a lower gear. By shifting to a lower gear, the engine will run faster and will cause more oil flow through the transmission cooler. That is the general idea that GM had by designing this transmission this way.

Now, not all of these transmissions have the temperature sensor. You will want to check this with a scanner and see if the trans temp is high. It will not turn on the check engine light.