From the SRT6 service manual:

DESCRIPTION - DIFFERENTIAL LUBRICANT

Note: Refer to the Owner’s Manual for the recommended differential lubricant change intervals for this axle.

Use synthetic SAE 75W-85 axle lubricant that meets MB 231.1, such as Mopar 05126035AA. An SAE 80W-90 GL-5/MIL-2105-E Synthetic Axle Lubricant may be substituted. Reduced axle durability may result if an unapproved product is used.


I looked through the owner's manual and it does not state any change interval.

EDIT: Fluid capacity: 1.3 L (1.4 qts.)