Rebuild transmission or is it the solenoid?

You'll just have to take the car to a mechanic that knows automatic gearboxes. It doesn't matter if I can give a solution online you'll not be able to fix it yourself in anycase. I have a lot of knowledge about a couple of cars and rebuild a couple but I will not even attempt to tinker on an automatic box. Replacing a solenoid might fix the prob but your not sure if it will so save yourself the trouble and have someone qualified look at it. Hope this helps you to get closer to a decision on what to do.

It sounds to me like a transmission failure, if what you are describing is potent smelly transmission oil this is due to the the fluid being allowed to seap past the internal valves that control the oil preassure, commonly known as 'slipping' this causes the oil to overheat due to the friction produced. Take it to get checked out and confirmed

Thank you Paul and MrRocket12

I have a 2005 Ford focus zx5, mine was doing the exact same thing I've been two three different mechanics...the first said it was my transmission oil pan gasket so I paid to have it replaced and all the fluids changes( oil and filter change, new transmission fluid, etc.) About a week later I still had the same problem after being told I just needed to drive it till the leak stopped. Took it to a second mechanic for a second opinion. Was told it was definitely a leak, he got underneath and discovered all the bolts we're loose on the transmission as well as the oil pan, he tighten them up added lucus and new oil, I was then told to drive it around until it stopped leaking..... Still no difference in the stalling, yerking and no reverse or shifting whatsoever!!! Took it to a third mechanic it took him less than 15 mins to tell me that the other mechanics we're definitely wrong and wrapping me off( being a female and not nowing anything about cars) he told me it was the rear seal of the transmission that was loose but because I had been driving the car hot while the oils we're leaking out quickly I burned up the inside of the transmission. He suggested the cheaper option of him rebuilding it himself rather than buy a new one or and old one that might not last.... I'm currently waiting to see how the rebuild is coming along