Also what is the recommended fluid?

Here is the relevant page from my 2005 owners manual. Looks like you need to figure out which rear end you have.

 

The 2008 6.4L aluminum cover fits.

 

I have the 10.5'' sterling axle. Is there any benefit in switching to the aluminum cover? It looks like it has provision for o-ring or use silicone? If silicone what type?

 

Rear Differential Pan: Permatex Black RTV sealant.

If you do not want to use Permatex, then there is a gasket that fits: Lube locker LLR-F105 (rear)

 

Is there any benefit in switching to the aluminum cover? More capacity? Better cooling?

 

People disagree on that topic. I tend to think that there isn't any measurable benefit.

 

Thanks for the info, think I will just re-paint the original with some high temp paint.

 

I think there is some cooling benefit, but most of that benefit is necessary when you get into the newer truck's higher weight capability. Is it worth it - maybe not.

 

There is a reason that a lot of dually's come with finned aluminum covers. Yes it does help. Having more fluid capacity also helps. Personally I like the covers with drain and fill plugs. Easier to service.

 

I think there is some cooling benefit, but most of that benefit is necessary when you get into the newer truck's higher weight capability. Is it worth it - maybe not.

There is a reason that a lot of dually's come with finned aluminum covers. Yes it does help. Having more fluid capacity also helps. Personally I like the covers with drain and fill plugs. Easier to service.

The only benefit is its easier to service and looks nicer.

 

So 6.0L dually's have larger differential covers? I wasn't aware of that (and am not sure I agree).

How many rear differentials fail? My gut says, not many.

How exactly does it help to have a larger volume cover? I don't particularly want to hear about lower temperatures (I agree that temps will probably be lower and have even seen 20 degrees reduction claimed), because that may not really help anything that matters, ie differential longevity! It is not the same as engine lubrication!

I have really only encountered one failed differential (not mine). Also, I have seen almost none discussed on the forums, although I certainly may have missed many of the discussions on it because I do not frequently peruse the general SuperDuty section.

I would bet a bigger issue is just plain lack of service!

 

How many rear differentials fail? My gut says, not many.

How exactly does it help to have a larger volume cover? I don't particularly want to hear about lower temperatures, because that may not really help anything that matters, ie differential longevity! It is not the same as engine lubrication!

I have really only encountered one failed differential (not mine). Also, I have seen almost none discussed on the forums, although I certainly may have missed many of the discussions on it because I do not frequently peruse the general SuperDuty section.

Ford generally has had a great reputation regarding their axles. Dodge, not so much. Dodge axles were notorious for failures. Separately, there was also a big focus a while back on the heat treating of parts leading to failure. Heat causes expansion, and widening the range of expansion will have its affects. Some manufacturers have their processes dialed in better than others. Would I be concerned enough to worry about it on a ford? No. Does cooling provide a benefit to axle bearing or seal longevity? Not enough data, but ford will sell you one.

https://accessories.ford.com/super-duty-14-bolt-heavy-duty-differential-cover-m4033sd14

An axle specialty shop here in socal with decades of experience building high prices toys and everyday rigs recommends higher capacity over fins. They have seen less failures on that setup. Axles is all they do everyday.

Most people aren't going on forums with axle issues. They take to a shop because of the degree of difficulty. I wouldn't base my assumptions on what you see on a blog.

Edit- fords diff cover does not claim lower Temps from what I saw. That says a lot.

 

In a forum, if someone has a diff failure, you will hear about it. People whine about every damn thing else.

There are a lot of things Ford doesn't say, but they do. Did you hear about the multiple changes to the design of the Superduty sway bar links in the early years?

I'd have a hard time believing that the temps are not lower. Aluminum has a higher thermal transfer rate, and you have a larger surface area with the fins for the thermal energy to dissipate. When you have the same basic design of differential, but increase to a higher payload, it is going to create more thermal energy. Track cars with oil pumps and heat exchangers are another example. They ain't going a 65mph speed limit.

Transmission / Differential Cooling - Pegasus Auto Racing Supplies

Protect those expensive gears and bearings while improving overall reliability by adding an oil cooler or filter to your racing differential, transaxle, or transmission.

www.pegasusautoracing.com

Engineers like to put fins on things they want cooler, like the Akebono rear caliper design of the '99-04 Superdutys. Ford was hyper about brake fluid boil (unnecessarily), and the rear calipers got cooling fins. No announcement, just fins.

 

For the transmission, a larger sump volume doesn't help. Previous posts of Mark K communicated to us that he has tested it while working at Ford. My recollection is that with any reasonable (minimum) driving speed and time, the engine has become hot enough to add heat to the air mass that is flowing under the truck. This air mass becomes hot enough that it doesn't provide any cooling (heat transfer) effect at the transmission pan. People still argue with him even though he has tested it and taken "measurements". So air flow across the transmission is in the 140+ range.

Now, has the hot (engine heated) air flow dispersed enough (or pulled in sufficient cooler ambient air mass) that the air flow across the rear differential would actually provide significant cooling benefit? Probably so, and also because our differential fluid typically runs hotter than the transmission fluid when under any load - in the 200+ degree range. Our differentials are adequately protected by the fluid (oil) in that range - assuming good maintenance practices.

This is why I asked earlier about the tangible benefit of running cooler - "what mechanical benefit would we see from a cooler running rear differential ......... in any significant way" (and I mean in actual "temperature related" failure data, not theoretical)?

Fins help in heat transfer because they increase the area of contact for the metal that separates the hot and cold fluids. This is why radiators have fins - they increase the area. Heat transfer follows the formula of Q=U*A*LMTD. where "Q" is the heat transfer, "U" is the heat transfer coefficient (applies to the design of the heat exchanger), "A" is the heat transfer contact area, and "LMTD" is the log-mean temperature difference. Increase the "A" and you can get more heat transfer (if all else stays the same). So also, one has to know the temperature that the differentials run at (at carious conditions), this is in addition to how quickly is heat generated and transferred.

I seem to recall that the temperature of our differentials was measured some years back by a forum person. Perhaps the tests were done at various hours of operation, ambient temps, and operating loads. I will have to look for those posts. I tend to save links to that type of discussion.

 

Found one old post on monitoring actual temps:

Differential Oil Temp ? - Ford Truck Enthusiasts Forums

6.0L Power Stroke Diesel - Differential Oil Temp ? - Anyone happen to know what the temp of the oil in the differential should NOT exceed? Thinking of installing a new cover with a temp probe fitting in it. Had engine oil temp gauge before I bought my scan gauge and want to hook up the probe to...

www.ford-trucks.com

 

So Bud's run was with an F-250, an SRW with the Mag-Hytek, which I got rid of and put in the Ford aluminum cover. Running in the PA mountains in 100ºƒ weather, no indication of weight in the truck or towing a trailer, got to 200ºƒ, ran in the 180-200 range.

Mark Kovalski, climbing I-70 west of Denver towards the Eisenhower tunnel with an F-550 6.0L at 30,000 pounds, got to 300ºƒ. Different differential, higher ratio, larger in size, heavier in weight, OE cover.

Weight matters along with the disparity of applications.

Just a smidgen of incongruity, other than somewhere between 200-300ºƒ. You live with what data you have ...

 

Totally agree, but the "gist" is what you said.... 200*F to at least 250*F is to be expected and is acceptable when working the truck! Even spikes to 300*F appears to be acceptable in short duration.

Even though I changed covers, it wasn't for added reliability - just the convenience.

Many people make the point that a drain port and a fill port makes it TOO easy (ie periodically removing the cover and cleaning out any "sludge" is a good thing).

At my age, the convenience is nice and frequent fluid changes is a good thing.

 

I'll always pull the cover to get the sludge out. It's amazing how much accumulates there.

 

Anybody test that fancy schmancy Gale "air density" Banks cover? Lol...

 

 

I was hoping this thread didn't take this turn

 

Here I was hoping for the complete opposite.

https://www.powerstroke.org/threads/aftermarket-diff-covers-they-work-banks-is-going-to-test.1347933/

 

I gotta stop by more often, i enjoy the opinions generally expressed in a friendly manner. Mark and Jack always good to hear yours. I put a finned aluminum cover on my truck, specifically for the cooling, fins = cooling. Is the cooling necessary? I don’t know, but this is what I told my wife and I am sticking to it. Psst, it looks way cooler too.

 

Yes, you do need to stop by more often.

I still refer people to your coolant flushing guide and use the images of your cooler.

And I have a YouTube channel now.

 

I second that Karl. Good to see you still around and hope all is well!

 

I switched to the finned oem dif cover because the steel ones rust
even fresh water will rust them when the paint bubbles and traps water as it normally does when a hot diff meets cool ramp water

the finned cover looks cool painted with sanded fins

 

This thread caused me to look at banks diff cover web page.

Banks Ram-Air differential cover extends lubrication life, retains fuel economy, and rejects heat faster than any other cover on the market.

when I read... retains fuel economy... I really hope people aren't falling for their marketing gimmicks..

 

Because cooler diff lube increases fuel economy?

I didn't get that memo. 🤪