Locking front & rear dif at the same time
 

Let's first make sure we are engaging them properly.

You have to engage the rear locker first then the front. The front will not engage without the rear engaged.

If you tried that then we definitely have an issue.

I can lock the front without locking the rear . I also can lock the rear without the front locked. But not both at the same time

confused: you have a 2008 with BOTH front and rear lockers???
Can you post a pic of your 4x4 controls please?

Really? I've never tried locking the front without having the rear locked first, but I never knew it had this limitation. :confused:

Learn something new every day.

This^^

I think we've found the problem. ;)

Also don't forget you have to be in 4 Low if they are factory lockers. The fronts will not engage until you have engaged the rear. More info and a pic of your controls would be helpful. Confused?

I bought an '09 Alpha with Offroad Package, because it was the FIRST year for front AND rear lockers.....

Do 2009 3.7L have front and rear lockers or is it an option?

Option