The water pump can be changed with the engin in the bay. However, you do not need to have the halfshafts hooked up to start it. As long as you have the intermediate shaft inserted in the tranny to keep the differential from droping down inside the tranny. I haven't seen this happen, but have herd cautions. However, consider this. You will not want to run the engine very long without having gear oil in the tranny, and you can not fill the tranny if the output shafts (axle) are not inserted in the tranny.
There is not much you can do wrong on the water pump. It comes with a rubber gasket, even if you didn't use extra selant, the rubber gasket will seal good if you torqued the bolts down properly.
So I'm guessing you pulled both halfshafts out before removing the old engine?? I should have warned you against that... to late now. It saves time and the need for an alignment if you seperate the drivers side CV joint, leaving part of the half shaft in the tranny and the axle hanging down. Then once the engine is free and ready to pull, you can moved it to the drivers side and seperate the pass side halfshaft from the intermediate shaft. This also saves your tranny fluid if you are not ready to change it.
If you have any questions or need advice tonight, just call me. I've been there, I promiss. hm 955-3096 wk 902-4406
Bill, 2003 3.5 SE Altima, Black with black leather, headers, full SS exhaust, lowering springs, adjustable shocks / struts, SCAFII, 20" wheels, SER Tail lights, Dual Halos around headlights, HID headlights and driving lights, Maxima Helical LSD.
2010 Maxima SV Prem + Tech package
2006 Vulcan 900 Classic