Differential covers 101

None of mine has a drain plug...maybe a newer truck some day...

You can deal with draining and cleaning a diff cover that has no drain plug...

After the first time using the old and VERY messy process...in reassembling the diff cover...clean the diff casting flange area REALLY good...down to the bare metal

Then apply non-silicone gasket glue/sealant/etc to the cast iron flange and gasket side touching it...maybe the new synthetic lube is more stable, but IIRC, synthetic diff lube reacts with silicone based RTV to leak...

Let place the diff cover on and hand tighten the bolts, but DO NOT torque it down. Let the gasket sealant set before torquing the diff cover bolts

Fill and forget about it till the next diff fluid change. I change mine out about ever 2 years

Then to drain the diff fluid...loosen all of the diff bolts about half way out and place your diff lube fluid catch pan underneath the diff

Then wack the center of the diff cover with a rubber mallet and the diff cover will pop off, but stay on the diff

The fluid will drain into your catch pan

Then remove the diff cover bolts after the fluid stops draining

Inspect and clean the diff innards

Replace the cover and tighten the bolts to spec. I've done this for years and years without ever having to buy another diff cover gasket

Cummins12V98 wrote:

LIKE2BUILD wrote:

SidecarFlip wrote:

Only thing I wish was my stock cover (Corporate 10.25) has a drain plug in it. ....

You could remove the gear oil with something like this Topsider Fluid Extractor.

Personally want to look at the condition of the gears and get all the lube out.

You're right, taking a look at the gears and cleaning out any excess material, and looking for shavings are definitely worth while. But for some who don't want the mess vacuuming out the fluid can work too.

charwan wrote:

bobsallyh wrote:
Over the years I've been a fan of looking at rear ends, but not finned aftermarket covers.....

I was a Ford mechanic for years and worked on many a rear end....Never saw but one rear end burned up....Waste of good money.

Some of the aftermarket extra volume covers may be more marketing hype than engineering need. However, if you look at RAM 3500's with the HO package (or maybe it's the dually models?!?) they come from the factory with the AAM aluminum finned cover....the exact same one I installed. I would guess RAM assumes you're going to tow/haul heavy loads with these 3500 trucks and want to ensure you keep the rear diff within acceptable operating temps.

I have times where I tow right up to my max, so I'd prefer to have the extra cooling to make sure I don't have excess heat issues.

KJ

ib516 wrote:

Groover wrote:
I find it interesting that the entire discussion so far is concerned with keeping the differential cool but Ram recently added a differential warmer on some trucks. Overheating is bad but so is overcooling. Finding the sweet spot for your application is the trick.

I think they added the rear diff heater for mpg reasons for times when the very viscous gear oil is cold - not sure where you're from but where I'm from, 80w90 gear oil is like a bar of soap at -40 and will rob mpg until it reaches operating temp. When we see the data from Banks on the running temps of gear oil, I suspect it will be higher than running temp of the coolant, or maybe RAM has a way of turning the coolant flow to the rear diff on and off depending on temperature.

Yes, it was added to warm up the gear oil to aid in MPG.

ib516 wrote:

Groover wrote:
I find it interesting that the entire discussion so far is concerned with keeping the differential cool but Ram recently added a differential warmer on some trucks. Overheating is bad but so is overcooling. Finding the sweet spot for your application is the trick.

I think they added the rear diff heater for mpg reasons for times when the very viscous gear oil is cold - not sure where you're from but where I'm from, 80w90 gear oil is like a bar of soap at -40 and will rob mpg until it reaches operating temp. When we see the data from Banks on the running temps of gear oil, I suspect it will be higher than running temp of the coolant, or maybe RAM has a way of turning the coolant flow to the rear diff on and off depending on temperature.

It is also important to cook off any moisture that tries to accumulate in the rear axle. For that you need to get the whole thing above boiling on an occasional basis.

Groover wrote:
I find it interesting that the entire discussion so far is concerned with keeping the differential cool but Ram recently added a differential warmer on some trucks. Overheating is bad but so is overcooling. Finding the sweet spot for your application is the trick.

I think they added the rear diff heater for mpg reasons for times when the very viscous gear oil is cold - not sure where you're from but where I'm from, 80w90 gear oil is like a bar of soap at -40 and will rob mpg until it reaches operating temp. When we see the data from Banks on the running temps of gear oil, I suspect it will be higher than running temp of the coolant, or maybe RAM has a way of turning the coolant flow to the rear diff on and off depending on temperature.

LIKE2BUILD wrote:

SidecarFlip wrote:

Only thing I wish was my stock cover (Corporate 10.25) has a drain plug in it. I have to pull the cover to drain mine, something I do every couple years.

You could remove the gear oil with something like this Topsider Fluid Extractor.


I bought one to use on my boat to change the oil, but it works great for remove diff gear oil as well. In fact, I've found several different uses in the garage so it's a pretty handy tool to keep around.

Personally want to look at the condition of the gears and get all the lube out.

Af far as boat oil drain I added a Fumoto and will add a clear poly tube and run out the drain plug hole into a bucket.

I find it interesting that the entire discussion so far is concerned with keeping the differential cool but Ram recently added a differential warmer on some trucks. Overheating is bad but so is overcooling. Finding the sweet spot for your application is the trick.

If finned aluminium covers weren't needed or didn't have a benefit, the OEMs wouldn't go to the expense of adding them. It's a fact that aluminium dissipates heat better than steel. Any adult knows that. It's also a fact that adding surface area (fins) to anything that is hot will make it reject heat faster with the same BTU input. It should be plainly evident that a finned aluminium cover of the same, size, and shape as a stamped steel one, even with the same volume of gear oil will run cooler. How anyone can debate that is beyond me.

Now, as far as it being necessary, only the OEMs or axle manufacturers know that. I'll trust that they employ engineers that know what they are doing and that they design an axle assembly that can stand to run at max GCWR/GAWR, uphill, in extremely hot temps and survive.

Some may say they have xxx,xxx miles on their rear diff without a finned aluminium cover and never had an issue, that's great. But remember the OEMs have to design for worst case scenario that you may never experience.

Kind of the same concept as a diesel tuner. The OEMs need to design an engine calibration that will work just fine in Alaska at -45* and Death Valley at 120*.

charwan wrote:

bobsallyh wrote:
Over the years I've been a fan of looking at rear ends, but not finned aftermarket covers. Can someone tell me how long the rear differential in our 2003 Dodge dually is going to run with 242,000 miles on the clock with the plain old OEM cover towing a 40' fiver?

I was a Ford mechanic for years and worked on many a rear end. What you said bobsallyh is very true. Never saw but one rear end burned up and it was a F350 were a boy got stuck and burned it to a crisp. Waste of good money.

No it doesn't happen often, but that doesn't mean it never happens. Carmakers wouldn't put all that money into R&D unless it was worth it!