Transmission shudders and wont upshift into 3rd gear??

[HeloMech82]

Hey folks! I have a 1995 T4R 3.0 2wd auto trans. I recently installed a remanufactured transmission and now it shudders when trying to upshift from 2nd to third. I have to let out of it and cruise at 50 mph because of it. Why only going into 3rd gear, I don't know. No check engine light. 130K miles. I've been told it could be the TPS but I figured that I would have noticed problems elsewhere if that went bad. The speedo bounces around maybe that affects the shift timing. I am lost and not sure where to start. So driving along you cannot pick up speed to get on the freeway either. It wont down shift to grab a lower gear, instead it shudder like it cannot decide what gear to go in.
Any help would be greatly appreciated. Thanks in advance

 

[Ahlem]

I was low on transmission fluid and had a similar problem. Added some and the problem went away.

 

[HeloMech82]

Yea I checked the fluid. I'm trying to figure out why, if it is the TPS, it would only affect certain shift points and not all of them. What a pain this is