Best Differential Fluid

[wdk450]

Gang:
I have become aware that the differential gears on our trucks towing heavy loads can become hot and lead to lubricant breakdown. I believe Dodge recommends fluid change at every 15,000 miles due to this. I have been looking at various differential fluid comparisons, and the data I've seen seems to indicate that Amsoil is the best. What do you use/recommend?

 

[porthole]

I replaced the diff cover with a Mag Hytec aluminum cover. I don't know if it really helps cool the fluid or not but what it does do is:

a change the capacity from about 2 pints to almost 8 pints
b has a tapped hole to add a diff temperature sender (which I did)
c has plugs so you can drain and add fluid without pulling the cover
d has a dipstick for fluid level

e looks real cool!

At the same time I added Amsoil. Actually, at that time I also replaced the trans pan with a Mag Hytec (same reasons) and changed all the oils to Amsoil (engine, trans and diffs).

I "may" change the diff oil after the end of the coming season and most likely will not change it after that.
The highest temp I saw on the hottest days pulling up hills was around 150, maybe a little over that.

Although I am still debating whether switching the engine oil to synthetic is worthwhile.

For the cost I could change the oil 3-4 times in the engine (not including filters).

I really think you can't go wrong swapping out to a high capacity cover and switching to synthetic in the axle. The Mag cover is almost quadrupling the oil city. The Mag trans pan adds almost 4 quarts capacity, which feel is better then just the "cooling" improvement.

I really would not want a differential failure on the road. One thing I learned in my career working at Chrysler dealers is most techs did not know how to overhaul axles. And if they did few did them correctly. Few dealers even stock parts for differentials.

 

[davebennington]

I changed out my differential cover as well as the transmission pan to Mag-Hytec aluminum differential cover and a double deep pan. So far I have seen a drop in temps in both the tranny and the differential. It would appear that the change has worked, I also use synthetic oil in both.

Dave

 

[khalsey]

I changed the differential cover on my Dodge to Mag-Hytech aluminum cover also. It changed fluid capacity from 4 quarts to 8 quarts. I have been using Valvoline Durablend (synthetic blend) 85W-140 for a few years now. Maybe not the best but good enough and resonable priced and easy to find in this location.

 

[jbeletti]

I looked at the Mag-Hytech website and could not find a cover for my rear diff. Too big maybe? 2007 F550 with 4.88 gears. Dana 110 I think.

Jim

 

[jimtoo]

Jim, I don't think yours has a cover. Your differential is pumpkin style... the whole thing (all the gears in one unit) comes out the front to work on it. The lighter units have a cover on the back side and must be serviced from that backend if needed.

Jim M

 

[HarleyRyder]

Jim-

Here is a picture of what your Dana S110 should look like and confirms what Jimtoo is describing.

 

[jbeletti]

Thanks guys - make sense now. Me and my big ol black pumpkin.

Jim

 

[HarleyRyder]

Jim-

Just a little more "down and dirty" research shows that your differential holds 14 pints of fluid compared to the 7 to 8 pints on smaller axle housings.

 

[branson4020]

so...

Belletti has a big rear end?

OMG, I'm sooooo sorry, but SOMEBODY was gonna say it, riight?

 

[HarleyRyder]

Yea, I knew somebody would go there. Some of us have pumpkins in the rear and some of us have pumpkins in the front.

My front pumpkin might hold 14 pints and my rear pumpkin can hold .......never mind.

 

[Bob&Patty]

I have always installed synthic fluid in my diff. I also witnessed a size reduction In JB's rear end size...the diet is working. Its almost the size of a 1 TN rear end now, not a 110 Dana. Kenny made me do it... honest. Bob

 

[lwmcguir]

I looked at the Mag-Hytech website and could not find a cover for my rear diff. Too big maybe? 2007 F550 with 4.88 gears. Dana 110 I think.

Jim

The differential in the F550 is large and has a huge service factor to pull 25,000 pounds or better. Due to that they dont heat up much and last many miles. We have >200K on ours and it is still tight and if great shape. I expect it to outlast another engine and transmission.

 

[porthole]

I also witnessed a size reduction In JB's rear end size

And just why are you witnessing?

 

[palebluedot]

+1 on the Mag-Hytec cover. I changed to it on the Dodge a year after buying the truck. I changed out the original fluid to Royal Purple 75W-140 when installing the new cover. Just be sure your oil has the friction modifier if you have a limited slip differential. I think all the synthetics have it. I know the Dodge does great with the RP without adding any. I don't use synthetic in the Cummins. Change it out every 5K miles. After talking to a guy pulling FEMA campers after Katrina that had over 900K on a 95 12 valve Cummins who used only Shell Rotella T 15W40 it convinced me.

 

[dieselengineer]

The Mag-Hytec is a great cover. Highly recommend, if your paint is peeling off on the OEM cover, it is the first sign that the temps are very high.

The motor oil now will have the SAE CJ rating, not as good as the CI-4 plus rating. Over time the CJ oil gets thicker and does not have the additives that the CI-4 has.

 

[rumaco]

I use Amzoil (not a salesman and not a fan) just found it to be the best for heat reduction. We put the ATF in the transmission simply because we were told it would drop the temp........it did by about 50 degrees overall. Who knows, but at the temps we reach pulling these 5ers it is a comfort to see a drop!

 

[porthole]

The Mag-Hytec is a great cover. Highly recommend, if your paint is peeling off on the OEM cover, it is the first sign that the temps are very high.

If the paint is peeling because of heat the axle is already toast.

 

[rumaco]

I really never thought about differential temp...............how hot does it get???? Very confused about this.

 

[lwmcguir]

If your truck is under sized for the towing task that it is being used for it gets hot enough to burn you. The larger trucks have the right size differentials and run temps that will allow long life. The newer trucks also require synthetic blend oils that had wear additives. Be careful when toping them off as they are oil specific to the manufacture and type. Most lube shops only have a couple of oils available. The newer ones also require multi viscosity as compared to the old units that could live with standard oils. Units shouldn't need to have oil added and when changing the oil be sure to get the right oil for the make and model of differential.