Wanting to change my front and rear differential fluids and was wondering what is the best oil to use. I was leaning toward synthetic and would like to know what some of you guys are using. Please specify brand and weight, thanks.

 

I use Mobil 1 synthetic

 

This is what I run (see link). I payed $12/qt for it at NAPA. There area few others that are top of the line also. Amsoil andMobil. I went with Royal Purple because we use it offshore and it has proven itself to me. Also it is easy to get like the Mobil oil. Amsoil I have never used but a lot of people on the forum have and love it. But my 2 cents would be to go with one of the 3 and you cant go wrong.......
http://www.royalpurple.com/prodsa/mgeara.html

 

I am going to try Redline. I am going to half and half the 75/90 and the 75/140.

 

I intend to use Amsoil Severe Gear 75W-90 when I change mine.

 

Purple.

 

Dodge is using synthetics in all the AAM axles out of the factory. I changedboth the front and rearout to Amsoil Severe Gear 75w140. I have read many threads regarding diff fluids, but the one discussion that stood out the most was over on Carson Dodge forums. Seems that DC has some kind of service memo regarding the need for all AAM axles to be on 75w140 when changing out the factory break-in fluids, guess the Mopar75w90 wasn't doing a very good job at lubrication. Since many of the dealerships also offer the Amsoil fluids, I thought I would just stick with what the dealerships are offering beyond the Mopar fluids. I am very pleased with how the Amsoil fluids are performing. I had a little shudder/hop with the Mopar break-in fluid, now with the Amsoil Severe Gear I have no shudder/hop at all.

 

FYI, my Dodge local service mangaer showed me the May 2007 update and the new 75/140 gear oil everyone is talking about is only for the 1500 pickups with the smaller axles, not the 2500 and 3500's with 10.5 and 11.5 axles. Our trucks still use the normal 75/90 synthetic gear oil as per the May 20007 update that I read on his computer.

 

Great info on the oil in diffs but to slightly change the subject does any one know or recomend fluids for the diffs since I am gonna be going to Fairbanks, AK and farther north where the extreme temps there sometimes hover well below zero for months. Any insight would be helpful

 

75w90 in your favorate synthetic flavor