I know the factory recomends changing the diff fluids at 15K but with the mag-hytech rear diff it doubles the fluid capasity. Im at 15k now just wondering if I should go 30K b4 changing it due to the extra oil and what not your thaughts please.

Chris

 

You could easily go 30K miles. I would be going 45K miles actually.
Here is a good thread that kind of covers your question.

https://www.dieseltruckresource.com/...c-t282049.html

 

I have a buddy who has gone 280,000 miles with regular covers without changing his diff. oil.......he also pulls a 40' travel trailer quite often. Not what I recommend, but what can be done.

 

I changed out my stock fluid and installed the MagHytec diff covers on my truck at the same time, I tested the fluid at 15K intervals, and at approx 30K, 45K, and most recently at 56K, all the testing reports said my diff fluid was good. I am running Amsoil 90w140 severe gear fluid. I decided to change the fluid this last test regardless of the oil report telling me the fluid was still like new and had no contaminants. This time I put in the Severe Gear 90w110.

It may be more about what diff fluid you are using rather than just the mileage, when I took out the stock fluid the oil test said that it virtually was way out of its visconsity range, did not hold up to the 15K mfr recommended timeframe.


CD

 

I'm using mobil 1 75w90 synthetic gear lube

 

I ran 50k on my last oil change and fluid looked good still.

I'm running stock covers, but probably stick to 50k intervals.

 

Running synthetics 50k should be fine. That's what I'm doing.

MikeyB

 

Despite the job they have to do, differentials hold up exceptionally well. Even with years of abuse, it's a good bet they will be trouble free even with using Dino oil in them and extended change intervals. Synthetic would not be my choice for fluid, But that is just me.

 

You do know that your truck came from the factory with synthetic gear oil and GL5 75-90 synthetic is whats used in it when replacing the factory fill?

 

As my front diff no longer moves, I will probably change oil in it every 5 years or so. The rear with the mag-hytec holds more Red line full syn, with 2 magnets to catch anything, will change oil in it someday. Drainplug in cover makes it easy. The chain in the CT no longer moves on the hwy but I will change the oil in it often.

 

Absolutely.
I also know it's a waste of money to me to use synthetic, especially when you consider how durable differentials are and that millions upon millions of them outlasted the vehicles they were in when Dino oil was the only game in town...

By the time you got any benefit from running the synthetic, you probably would no longer own or want the truck. (I plan on owning mine 20-30 years.)

Carol mentioned earlier in this thread the STOCK synthetic fluids were failing sample testing at the recommended replacement interval. I don't know ANY Dino oil that would fail in 15K miles even under severe conditions.

 

Being that AAM states to use 75/90 GL5 Synthetic gear oil that is what I use. Also if they thought Dino gear oil would be as good they would have used it instead of synthetic.

 

I'm in the same boat with the mag hytec cover and the 15K change interval. Previous trucks I've had were factory synthetic and recommended 100K or basically "when contaminated". I use the Mobil 1 75W-90 as well. I'm going to use the magic dip stick and look at the fluid before investing another $80 replacing usable fluid.