99 monte carlo

I cant figure out if its the transmission or the control modular. we can shift to anything its just drive and over drive that doesn't register anymore. you can shift to anything else and it works just fine. please help me out. I have two vehicles that are acting up and I need to get to work with at least one of them. thanks

So, first and second gear are ok, but no third or fourth?

Scanned for codes?

Check fluid level and condition? Does this have a dipstick?

its an automatic. I have reverse, natural, first, and second. just not drive and overdrive. fluid levels are fine. we also replaced a sensor. it does have a dipstick.

If you have a dipstick, you have a 4T65E transmission....

Well, unfortunately, you have an internal problem.....about the only thing you can do, is have your vehicle scanned for transmission codes....places like AutoZone will do it for free.....what you are looking for are P07XX codes....

Have tried to manually shift the tranny.....put it in 1, when it gets to 2500 rpms, shift it to 2,....when it gets to 2500 rpms, shift it to 3...does it shift manually to 3?

Surprised your fluid is not dark colored and have a burnt smell....