95 oldsmobile 88 transmission
 

So I have a 1995 olds 88 royal. It has 91k on the car and has been a great car for a daily. I purchased the car 6 months ago. Recently, the overdrive has been dropping after about 10 miles of driving and will not go back into o/d until I shut the car off and let it sit for at least 30 min. I'm changing the fluid and trans filter next weekend and I'll go from there. It has the 4l60e trans and is not the supercharged model. Any help is greatly appreciated on what could most likely be the issue, thanks
https://cimg5.ibsrv.net/gimg/www.gmf...04c48c8dff.jpg

What do you mean by this? Engine freewheels? It shifts to 3rd? Something else?

When was the last service done on it?

How full is the fluid?

How many miles have you owned it?

It drops into 3rd and stays there. I bought the car 6 months ago ive had it for 10k

When was the last service done on it?

How full is the fluid?

No clue when the last service was done. The fluid level is good, red color, no burnt smell. I'm doing a fluid change and filter change as we speak.

When it does this, does it shift down to 2 and 1 normally, or does it stay in 3rd?

It will shift through 1, 2, and 3 gear just fine when the overdrive stops working

Overdrive or lockup?