I've been working through the major service list on my 2003 and drained the fluid from the transmission. I replaced the filter and cleaned out the sump pan and magnet. I followed the procedure filling the sump back up then continuing to fill it while it was running.

Since servicing the transmission, it has started to make a whirring type noise when in reverse. It only makes this noise when started from cold and the noise goes away after it warms up. The transmission still shifts fine and I have not noticed any other changes.

I tried draining/filling it again and I added a bottle of lubegard. It is still making the odd noise in reverse from a cold start.

Any ideas or things I should try?

 

I have the same noise but mine does it all the time in reverse, warm and cold.