what's the difference btwn the front and rear differential on a 2005 RL?
Are they both part of the rear differential( with a front and rear chamber)?

What's the cost to change each one at the dealer?
How often should it be changed? every 15,000-30,000 miles?

thanks in advance

 

There is only one diff at the rear axle, and it has 2 chambers. IIRC, the front chamber takes just over a qt and the rear takes just over 2. The manual will tell you how much and how often.

 

so at the dealership, is it
front differential fluid change -$90
rear differential fluid change-$90
total=$180

or is it
rear differential fluid-$90(for front and rear chambers)?

 

I can't quote a dealer, but the diff service entails both chambers. It is only one charge. Just make sure they refill both chambers, or you will end up with a new diff like Heavy did.

With an oil pump and a way to get the car off the ground, it's an easy DIY.