Your sure the car is not going in to 4th. Could it be the torque converter not going in to lock up? If your cruising at 50mph, then hold the gas at that speed and tap the brake. Does the RPM change?

I never paid attention to that, I'll try that today and report. It does sound like its shift but when I let off the gas at higher speeds there is a loud,high frequency, low pitched humming that I thought was just road and tire noise until recently. And like i said if im going 50+ and drop it to 3rd the rpm goes from 2k to 2500 and i feel a slight lag but not a huge one.

No rpm'* do not drop when i tap the brake at 50+

Take a look at this. https://www.gmforum.com/electrical-133/tcc-solenoid-switch-284972/ It'* possible it'* simply your torque converter not going in to lock up.

I just went driving again and at 55 i tapped the brakes and the rpm'* jumped a bit

Well thanks to a bunch of people in my automotive class last night I've concluded the trans is fine and the cv axles need to be replaced (hence humming) and also the ball joins (Hence knocking when turning)

Good to hear. And to answer the above post, if the RPMs jumped a few hundred, then the TC is locking.

Right i read throough the post you did a couple back about replacing it, thank you for your help.

No problem at all. Glad to help.