Transmission will not shift into overdrive or fourth gear

Hi,

Did the fluid totally drain? Is there anything other than 4th/OD that is being affected? Does it shift properly in the other gears?

Now that things are back together, is the ATF clean and full? Is there any evidence of air in the fluid or contamination from coolant?

Let me know. Also, try to retrieve diagnostic trouble codes to see if there is anything that may help us. You don't need a scanner. All that is needed is a short jumper wire or even a paper clip. Here is a link that explains how it's done:

https://www.2carpros.com/articles/buick-cadillac-chevy-gmc-oldsmobile-pontiac-gm-1983-1995-obd1-code-definitions-and-retrieval-method

Let me know as much as you can. Also, if you find there are codes stored, let me know what they are.

Take care,

Joe

Hi,

Thanks for the update. A delay in reverse (which requires the highest line pressure) can simply be the result of the fluid condition in extreme conditions. By chance, were you able to check for codes?

I'm starting to question the shift linkage. On 4-Speed automatics, it is possible to drive the vehicle in 3rd gear rather than "overdrive" and not perceive it. Typically, this condition occurs when the shift indicator or the shift linkage/detent is misadjusted. Misadjusted shift linkage can also result in improper signals to the ECM, which can result in less spark advance, and results in a drop in fuel economy.

I'm questioning this because what happened that seems to have led to the issue shouldn't have caused this to happen. Running for less than 5 seconds wouldn't have emptied the fluid.

Do me a favor. Let's see if the shift linkage is out of adjustment. When you were working on the vehicle, anything could have happened.

If you look at the pics below, they explain how to adjust the linkage on this vehicle. Take a look through them and let me know if you are comfortable performing them. Additionally, I am making the assumption that this is an S-10 Blazer and not a full size. If that is incorrect, please let me know.

I will watch for your reply.

Take care,

Joe

See pics below.

Try adjusting things. If that has been the case, there is a chance it is finally far enough off that it is causing the issue. Although you see it off in the vehicle, it could be off at the transmission and causing this.

I know I read a technical service bulletin (TSB) similar to this in the past. For the life of me, I can't remember it 100%. I will keep looking for it and let you know if I find it.

It may seem like a long shot, but again, I don't think what happened hurt the transmission.

Let me know.

Joe