The check engine light comes on and the car will not shift into overdrive or 1st gear

When was the last time that you had the transmission serviced? Sounds like something is plugging the valve body.

you need 1 and 2 shift solenoid and the overdrive shift solenoid

shift solenoid needs to be replaced or the speed sensor

the overdrive is the 4th gear. considering that it may not be an issue with your computer switching gears to fourth but an issue with the transmission itself. this light could be a signal instead of and engine warning light where the engine is fine but the transmission isnt.

I would check into the Trans oil temp sensor,they are known to keep the trans from shifting into 4th gear if they have a open or a shorted circuit...This may also be the culprit for the other issues you are experiencing when the trans is at diff temps and doing diff things....The other thing that is known for going bad in that Transaxle is the Sunshell...The splines on the inside of the sunshell strip out and than you will lose pretty much all forward gears,Except for 1st gear most likely and you will also lose Reverse if the Sunshell goes bad...But this will not act any different if the temperature is cold or hot

it may be a bad transmission modulator valve located on the side of your transmission,vacum operated. a sudden downshift or forward shift when unexpected is sign of a bad modulator valve or a vacum leak to the transmission.best to shop around for a garage w/references when it comes to transmission work though. check all the vacum lines to your transmision,you need to look on the underneath side of your truck on the side of transmission for a loose or disconnected vacum line on the side of the transmission. when you feel the vacum line,follow it to the top of engine,the vacum line is about 3/8th line,and may be disconnected or losing air. to make this short,when you drive the car,start out in low gear and shift the transmission,manually from 1st to 2nd to 3rd does it do right with no slipping? if it does this right and shifts great manually,the modulator valve on the side of the transmissions bad,or a bad vacum leak in-between.thank you for choosing fixya.com

Have the vehicle scanned.The overdrive light is like the check engine light for the transmission. There are transmission codes in the ecm if the overdrive light is blinking.

i got a 1996 chev. blazer s-s10 4.3 engine 4x4.problem i got is i got 1st 2nd & overdrive & reverse but no 3rd gear what should i do

Your transmission fluid contain water,thats why the colour of the fluid changed to pink.And of such the clutch is slipping causing the engine to reve up before shifting - Check transmission cooler.

The blinking overdrive button is telling u that a serious fault has occurred in the electronic controls or a mechanical fault such as excess slippage is occurring.