bent my differential cover -- plus fix

[cewillis]

Bigger images are here.


Bent the bottom of the differential flange. Without a rock guard, it was bound to happen eventually on some of the 'roads' I drive. Very minor leak though.


Old vs new


Looks like tank armor


Old: ~1/16", new: 3/8" steel




Test fit


After some cleaning, and several clear coats.
MUCH stronger, 3/8" steel body and flange, 5mm longer grade 8 bolts, increased bolt torque from 30 to 40 ft-lb.
But I still need a rock guard -- working on it.


Alien view

[Tom_Anderson]

ticki2 wrote:

cewillis wrote:

NRALIFR wrote:
Easy fix for the fill hole: I suggest the use of a "Digitus Secundus Manus" (index finger) to check the oil level. The bung looks plenty big enough.

:):)

We think alike, friend.

Yep , a little common sense goes a long way . It does beg the question , since it is probably an axle specific cover , why the fill plugs isn't at the correct level to begin with . I am sure it is not a cheap cover .

The plug is higher than normal because it's very common in the off-road world to rotate the axle housing for a better pinion angle and more clearance. It's much easier to use a finger to check the level than it is to park the truck facing downhill to get enough oil in it.

I have those covers on both ends of my rock crawling rig and they have proven to be pretty much indestructible.

[cewillis]

GeoBoy wrote:
Mag-Hytec said no way, it can't be a 14 bolt cover, it was.

Could your 2005 have had a Corporate 14 bolt ?

[GeoBoy]

silversand wrote:

CE Willis wrote:
The AAM 11.5 is used with all Duramax and 8.1L gas engines, and many Dodge trucks. (from 2003?? until current ASAIK)

....thanks for the clarification....I'd completely forgot about that monster 8.1 L gasser motor (with Allison) and big ring gear LOL

I had a 11.5" AAM in my 2005 Silverado 3500 SRW 6 liter gasser, Mag-Hytec said no way, it can't be a 14 bolt cover, it was. My 2015 GMC 3500 dually has the same rear gear.

[silversand]

CE Willis wrote:
The AAM 11.5 is used with all Duramax and 8.1L gas engines, and many Dodge trucks. (from 2003?? until current ASAIK)

....thanks for the clarification....I'd completely forgot about that monster 8.1 L gasser motor (with Allison) and big ring gear LOL

[cewillis]

ticki2 wrote:

It does beg the question , since it is probably an axle specific cover , why the fill plugs isn't at the correct level to begin with . I am sure it is not a cheap cover .

Yeah - kind of stupid plan, or result to put the hole too high. But, the right oil level is not up to the stock fill hole anyway - should be ~~1/4" to 3/4" below.
Cost was about $140, plus $20 for a high quality gasket, plus $6 for 9/16" Allen bit, 1/2" socket. Why the &*#% didn't they just make the plug use a 1/2" socket drive???

[cewillis]

silversand wrote:
...nice job Cal! Those massive 10.5 and 11.5 GM Corporate (later, made by AAM) diffs are freaking awesome. I think that the Allison 1000 tranny with Duramax comes with the 11.5 inch rear end in the 3500?

The only thing with these big 14 bolters is: ....you know a GM Corp axle has been down the trail when you see plow furrows down the middle of the offroading trail LOL...

I think the only way to get that pumpkin higher off the trail is with very large diameter tires (and a change of ratio to ~4.56 with ~41-9 teeth...and fly-cut that big housing down an inch or more-ish).

The gear oil quantity is very well known for those diffs...after you put in the correct quantity, you bench-mark the level through the filler hole with a 90deg bent white wire tie..marked with indelible black marker..and throw that new tool in your glove box 😄

Silver,

The AAM 11.5 is used with all Duramax and 8.1L gas engines, and many Dodge trucks. (from 2003?? until current ASAIK)

You're right about the larger tires. No other lift actually gains any (diff) ground clearance.

Your tool suggestion might work better than my finger --

[ticki2]

cewillis wrote:

NRALIFR wrote:
Easy fix for the fill hole: I suggest the use of a "Digitus Secundus Manus" (index finger) to check the oil level. The bung looks plenty big enough.

:):)

We think alike, friend.

Yep , a little common sense goes a long way . It does beg the question , since it is probably an axle specific cover , why the fill plugs isn't at the correct level to begin with . I am sure it is not a cheap cover .

[SugarHillCTD]

Nice fix.

On our previous truck, '06 Chevy 2500HD 4x4, the rear diff developed a pinhole leak due to the cover rusting through. I had never seen that happen but it shows how thin the OEM cover is.

[silversand]

...nice job Cal! Those massive 10.5 and 11.5 GM Corporate (later, made by AAM) diffs are freaking awesome. I think that the Allison 1000 tranny with Duramax comes with the 11.5 inch rear end in the 3500?

The only thing with these big 14 bolters is: ....you know a GM Corp axle has been down the trail when you see plow furrows down the middle of the offroading trail LOL...

I think the only way to get that pumpkin higher off the trail is with very large diameter tires (and a change of ratio to ~4.56 with ~41-9 teeth...and fly-cut that big housing down an inch or more-ish).

The gear oil quantity is very well known for those diffs...after you put in the correct quantity, you bench-mark the level through the filler hole with a 90deg bent white wire tie..marked with indelible black marker..and throw that new tool in your glove box 😄

[cewillis]

NRALIFR wrote:
Easy fix for the fill hole: I suggest the use of a "Digitus Secundus Manus" (index finger) to check the oil level. The bung looks plenty big enough.

:):)

We think alike, friend.

[cewillis]

jefe 4x4 wrote:
Cal,
I suggest grinding off about 1/8 of an inch along the bottom of the cover so it's not the first thing to drag.

Jefe, actually the bottom of the case has a lip that extends about 1/8 below the bottom of the cover. (you can see that in the first picture)
I've looked 'everywhere' for a skid plate something like this, with no luck. Guess I'll have to make/have made one.

[NRALIFR]

Easy fix for the fill hole: I suggest the use of a "Digitus Secundus Manus" (index finger) to check the oil level. The bung looks plenty big enough.

:):)

[cewillis]

trail-explorer wrote:
It needs paint.

--- several clear coats. --- I like how it looks without paint.

[cewillis]

Home Skillet wrote:
That fill plug looks way too high up. You will be over filling the rear end,which will cause axle seal leaks.
Just my $0.02

Spent some time on this question - so yes, I was aware of the issue and thought about it. And DID NOT fill to the fill hole, which is 3/4" higher than stock. The correct level is as stated here: 'The correct oil level should be between the bottom of the inside of the axle tube and bottom of the axle shaft.'

I measured to the bottom of the axle tubes on both sides, and also used a good level to locate the (outside) bottom of the tubes on the differential cover. Added 1/4" for the tube thickness, and added 1/4" above that -- which is still well below the axle shafts.
That procedure defines the max fill level, in my well-informed opinion.
In the second to last picture, one may notice an 'etched' mark on the cover (made by me with hammer and chisel). That is the max fill line.

I admit it was a little 'tricky' determining when the oil level was at max -- but it is. Takes 4.5 quarts Amsoil 75-90, minus the small amount left in the bottles and the funnel.