My 3500 4x4 has about 6700 miles. I have not done any towing with it yet. When should I change the front and rear differential oil? Thanks for any replies.

 

I would go by the color changing , getting dark or looking like metal flake paint .
Or if it starts looking milky , water .
Differentials can go a long time between fluid changes , its the only fluid / lube that I do not go by my rule of , nothing stays longer than 20,000 miles or 1 yr. , that is everything , coolant , trans fluid , brake fluid , grease , engine oil I go by oil analysis for change .
Diffs can be OK past 50,000 & more , but pull the fill plug now & then , stick you finger in , to check for level [ about 1/2" below fill hole ] & how it looks , the harder you work the truck , the more often you should change all of these .

 

John`s got some good advise and it all sounds reasonable. My `06 owners manual says don`t change it unless there is evidence of water contamination. My service advisor says 15,000 miles. Being form the old school and hardly ever changing gear lube, I questioned his advice and that`s when I read the manual. A fellow on another Dodge Cumins forum changed his at 22,000 and said it was yucky, both front and rear. Now, I don`t know if his was water contaminated or not, but it made me think I should at least look at mine and see what`s going on. Any strange appearance would be cause to change it in my opinion.

 

Does not the owners manual mention severe use service at 15k intervals and lite usage as long as never?

 

Owners manula will say every 15,000. I changed mine out the day it came home from the dealer brand new.. It was already milky and yucky from the assembly lube. Had consistency of WATER.. I would change it ASAP

 

Just make sure you use Mopar Synthetic 75w-90 these diff's get extremely hot when towing and synthetic is only fluid recomended for extreme heat. These American axle's are bullet proof as long as you change the fluid when required. Much better then the Dana 60 & 70 trak-lock. That is why Chrysler dropped them for use in Dodge trucks. Their failure rate was so high, kept me very busy rebuilding these.

 

You sure for lite usage its 15k? It needs to be a synthetic correct gear oil but it does not have to be Mopar.Many good gear oils out there.As far as coolant its rated for 5 years.Lets not get carried away and waste lots of coin needlessly.

 

I never got into changing diff. oil, but I only run them 14-15 years and 100,000 or so.

 

Yes you need synthetic and in my 07 5.9 owners manual the interval is 15,000. Still a bit excessive but going to stick with it. I tow heavy so I run AMSOIL 75/140 GL5 Synthetic...

 

I did my first one at 30,000 miles. Fluid looked fine with some towing. Severe is every 15,000 miles and normal is every 30,000 miles. Don't let the first change scare you. They paint the gears with a grayish stuff to prevent rust I would assume. So the first change will look a little milky brown looking. No big deal.

 

to me that read like: How far can I pull my truck into the garage? I just go until the sheetrock cracks, but don't go too far or you'll take out the wall.

 

What if his garage wall is 36" of concrete?

 

I change the differentials and transfer case every 14K whether I think they need it or not.

Two trucks ago, the tech told me if I don't do the service intervals by the book and I get a failure, they won't warranty it.

I use the truck hard. That's enough for me.

 

Just my $.02 but I would change it because the gears "breaking in". After the first change I`d only change every 50,000 miles or so.

 

..guess we'll listen for the crumple of the front.