2000 Mazda 626 Desperate for help

[coldie9912]

My sons 2000 626 4cyl is going crazy. The check engine light came on while driving. The next day after driving a few miles the engine would try to change gears while at about 55 mph. The rpm's rev high and it will down try dn shifting. The tranny was rebuilt about 2k miles ago. Since, I was told that a tune up might help. I changed plugs,wires,coil, and cleaned the Mass flo sensor and the Egr gauge. When in park in runs great and revs great. When cold it will run perfect for about 2 miles at 60. Then it will start the changing problem again. When you slow dn it is not as bad but does seem to be getting worse at the lower speeds as I have test driven it during the process. But again for the first few miles its great. This has been going on for a few weeks and I can't get anyone to help. The trans fluid is full but did seem to drip off the stick a little easy. Not sure how thick it should be.
Please help, my son is using my car and driving me crazy.

 

[JKPgt96]

It sounds like perhaps the trans is slipping? Maybe an issue with the torque converter? Have you taken it back to whoever rebuilt the trans to have it looked at? Or take it to a dealer and have them at least diagnose it? I am not very familiar with auto transmission, sorry I cannot help more.