I am changing the fluids in my 2004 ram differentials. I see I need 75W-90 and 75W-140. The OEM Mopar Syn fluid is $31.00 at dealer but I can get it for $25.00 on ebay. I was also thinking about going to Royal Purple or Red Line lube. Has anyone done the change and what do you think ? They are all GL-5

 

 

Agree. You have the specs correct for the front and rear diff. Goto your local autoparts box store (aka NAPA or ? ) and buy the oil. You do want full synthetic. You do not want hyped up marketing products as they are extra cost with no benefit. Get a mainstream name brand oil that meets the specs. My last change was 14$ a quart front and back, same price different weight. Shop around. Do not mail order. Goto the store.

 

It be a Cold day in Hell that I'd buy that Mopar stuff.....

 

Here is the most recent fluid line up poured into my Ram. Front to back.