So I'm working on my girlfriend's Malibu... It's a 2001 Malibu LS. Whenever we put it into reverse there's this loud clicking/ticking sound coming from under the hood. I haven't had a chance to narrow the source of the sound down yet, but in neutral or drive there's no noise at all. It seems to run and shift just fine, but we're gettin ready for a long trip and don't wanna find out the hard way that it's a major problem. Of course I can't check the transmission fluid(still not sure why they did that), any ideas???? Thanks in advance for any help!

Axle maybe?

I wouldn't imagine that would be likely... The noise is present whether it moves or if you just sit there in reverse with your foot on the brake...

Well on FWD cars clicking is usually an axle, CV joint or CV boot issue.

Mine does this as well. I have never been too concerned by it. I have made several long trips with the car.