1996 sunfire 2.4L shifting problem 3rd to 4th gear

[mega8man]

My sunfire is not shifting from 3rd to 4th gear. I will shift fine all the way up to 3rd and then ir revs like it is in neutral when i hit about 43 mph. it gets a little bit of a jump if i get off the gas all the way and then back on it and i can get it up to 55 but the rpm's are at 4.5. I read a few different posts that seemed like they may have had the same problem but they werent describing the way my car is acting. I went and got the fluid exchanged today and also changed the throttle position sensor on a whim because someone told me it could be the problem. Oh and if you couldn't have guessed by the post it is an automatic.
Any ideas or test i could do would be greatly appreciated. Thank you!

[Tech II]

Were there any codes, like shift solenoids?

What was the condition of the old fluid? Did they find any metal in the pan?

Certainly sounds like an internal problem.......

[mega8man]

Alright! I'm sorry it took me so long to reply. I have been working on getting my code reader to work since the port was a little screwed up on the car and i couldn't pull the codes. But now i have the codes. hah too bad i still dont know anything about transmissions.. well the codes i pulled were:

P0753 Shift Solenoid A Electrical

P0758 Shift Solenoid B Electrical

P1810 Manufacturer Controlled Transmission

P0113 IAT sensor 1 High Input

When I had the transmission fluid changed there were no metal shavings in the pan.

[mega8man]

Does anyone know how difficult it is to diagnose the shift solenoids? I wouldnt know where to start or how to test them.