Front and rear differential service - How long on synthetic oil?

[Hitec.Redneck]

My intention is to not start a Ford vs Chevy vs Dodge conversation but after spending almost $300 for Aisin ATF fluid, Mobil 1 front and rear synthetic differential oil I am not sure if I agree with the books suggestion to change the front and rear differential oil at 15K miles. Mine had almost 20K on it and when I drained it out it looked as good as the new oil I put back in. I wonder who else thinks changing the differential oil at 15K miles is too soon? I know oil is cheap compared to repairs and in my case the labor is free (me) but I doubt I will change this stuff again at 15K miles.

 

[RVTRKN]

30K+ and not think twice. When I got my 04.5 I was told 15K, when I got my 07 I did the 15K like the 04.5. It was a total waist of money. The last dealer change was at 30K and I just did them myself at 70K for 40K on the oil and it came out like new.

 

[nukegm]

comrade - all my gear buddies say 30k here in colorado. many of them own shops. just my .02 cents. cheers!

 

[KATOOM]

All lubricants follow the same rules of running temps, contamination, and change intervals...

The "synthetics" you buy on the store shelves are nothing space age but merely specific additives with uni-formally symmetric molecules during the refining process. That symmetry keeps oxidation to a minimum which is why synthetic lasts longer than conventional. Lots of people are surprised to learn that most synthetics are from the same crude oil that conventional oils are made from.

Anyways...without rambling on, its best to change out the factory differential fluid not too long after break in. Probably 10k - 15k miles. Then refill with a quality lubricant or put OEM back in. But just base the weight and type on what you're doing with the truck and the ambient temperatures where the truck is used.

After that, change intervals should be based on how hot the differential runs and how often you tow and/or tow heavy. Meaning, any fluid which runs 225*+ on a regular basis should be changed more frequently. But everyday cruising down the freeway empty places almost no strain on the fluid and will allow it to last for considerable longer.

All that said, the best way to monitor would be with a temperature gauge on the differential. I installed one years ago and it helps me know whats going on under there.