Could be some air moving around in there.... mmm... I replaced mine today. WOW! If you decided to replace it, either because you need one or just for S&G's.. INVITE a friend over! I will tell you that there is an O2 sensor plugged in on the back of the engine. I would also suggest that you remove all the wiring from the transmission before you drop it out. The back end of it is the heaviest, But I could pick it up by myself.
The method I found easy?
I drove the power ranger up onto ramps and chocked the rear wheels. This gave me pleanty of room to work.
Drain the OIL!
Drop the drive shaft. Though it may not be nessary, I would suggest that you spray paint the driveshaft and yoke on one side so you put it back on in the same way.
Remove the exhaust. You will need a deep 15mm socket for the manifold side. I'm not sure what side nuts/bolts are on the tail pipe side.
I hope you have two good floor jacks and some 2X4's about six inches long.
Unbolt the two bolts holding the transmission to the crossmember. Jack up the tranmission on the back side using the 2X4's between the jack and the tranny.. and then remove the crossmember. Using the other jack or jack stand and some more 2X4's, support the engine.
Now for the tricky part. If you are feeling froggy, and have some strength about you, SLOWLY have your friend support the bell housing while you pull on the shaft end and TADA! My paw-in-law and I used this metod and it work ok. Others may have some nifty tools but it worked for us.
Now here is the crappy part. Once you get it out, The slave takes all but 30 seconds to replace.
Finally, reverse the process and you are done! O! Do not forget to replace your tranny fluid!
Hope this helps!