Rear differential covers

[campigloo]

I’m getting ready to have the rear diff serviced and am considering adding an aluminum cover with heat sink. Have you gone this route? Does it make any significant difference?
I have 155,000 miles on my truck and looking at a leaking pinion seal. I have changed the synthetic lube every 40,000 or so miles. Not sure the cover would be worth the $300.00 for it.
Your opinion?
Thanks!

[LIKE2BUILD]

falconbrother wrote:
I have replaced the outside axle seals more than once. I have it down to a 1/2 day job.. It seems that there's a fine line to how much fluid goes into the differential. On the GM 1500s you just cannot overfill it but, measurement is an acquired skill. Most of the youtube repair videos say fill it till it runs out. Do that and tow and it will start leaking. I stay closer to what GM recommends and so far, so good.

I installed the unitized seals from Torque King 4X4. I also bought the seal driver tool.

I haven't towed yet, but we'll see if I kicked the problem this time. I used 4 quarts of gear oil and that put the level right at 1/4" below the fill hole. Between the better seals and proper fill level this hopefully be the last time I have to tear into these things.

KJ

[falconbrother]

I have replaced the outside axle seals more than once. I have it down to a 1/2 day job.. It seems that there's a fine line to how much fluid goes into the differential. On the GM 1500s you just cannot overfill it but, measurement is an acquired skill. Most of the youtube repair videos say fill it till it runs out. Do that and tow and it will start leaking. I stay closer to what GM recommends and so far, so good.

[LIKE2BUILD]

LIKE2BUILD wrote:

LIKE2BUILD wrote:
Amazon has the 11.5" AAM finned cover for $227. The Ebay price of $190 with shipping included seems to be the lower option out there.

I've had leakage issues with my outer hubs and have some planned work soon. I'm going to be replaced outer hub bearings and installing unitized hub seals so I thought I might as well get this finned cover and install that while I'm at it.

I'm not sure if my seal leaking issue is related to poor seals, sealing surface, heat, or blocked vent tube. I'll certainly look into all of those, but the decreased temps created by the finned cover will certainly be a nice bonus.

KJ

I received my AAM aluminum finned cover on 3/26/18. Wow, that thing is a substantial piece of metal and the fins are HUGE!!!

I'm hoping to tackle my hub seals in the next 2 weeks and I'll install the new cover at the same time. I don't know that I've had any heat issues, but this thing will certainly ensure that I don't in the future.

KJ

I got a chance to dig in to the rear axle about a week ago. I had to slightly modify the cover because the last fin on the driver's side was hitting my sway bar. No biggie, I just reduced the height by about 1/2" with a cut off wheel and all was good.

Outer hub seals were leaking between the seal and the hub, not the seal and spindle. Axle vent tube was free and clear both into the axle and out the valve. So really I have no idea what caused the seals to fail. This time I did use a coating of RTV Red(high temp) between the seal body and the hub. I'm really hoping this is the last time I bother with those.

Quick Note: If you get the AAM diff cover, it comes with really nice bolts but they use a TORX socket. DO NOT use a 12-point socket because that will strip the head.

Here is a pic of the new cover:


I was disappointed to discover my differential has an open carrier. :? I could have sworn the window sticker showed it had the 'Anti-spin' rear axle, but I guess I'll have to look at that again. I wish it did have the limited slip, but the limited slip diffs for this axle are about $700 plus installation. I think I'll just rely on the 4X4 knob to get me through.

KJ

[Cummins12V98]

Just a FWIW I recently was towing at 33K combined it was in the upper 80's outside and the center of the rear Factory cast aluminum diff cover read 155. This was shortly after a long pull into Pahrump, NV.

[Durb]

deltabravo wrote:

agesilaus wrote:
For what they charge they better look nice, $200 for a couple of pounds of stamped aluminum is overly expensive IMO.

The ones I've seen aren't stamped aluminum, they are cast.

I bought a cast one (BD) mainly for the drain plug plus I had to remove the old one to change the fluid. People spend over ten thousand dollars for electronic gismos for their trucks and beautiful wheels and tires then drive around with an ugly diff. $200 is a cheap visual upgrade in my mind. Any performance upgrade is a plus.

[Jarlaxle]

BenK wrote:
Agree...but...their gearing is way different...

IIRC.... 1st gear (out of about 18) is around 10:1 and their diff is around 5:1 to 7:1

carringb wrote:
Class 8 tractors don't have much more horsepower than our light-duty trucks. Horsepower = energy = heat. And the heavy haul rigs do have diff temp gauges, so they know they need to engage another axle.

No way. Every tractor at work has axle gears in the 3s. I recall 3.64 with OD or 3.30 without. My single axle truck has 3.90s.

[Jarlaxle]

Groover wrote:
I have been considering adding a finned aluminum cover but the price does seem high. The owners manual for my 2016 F150 does recommending changing the oil to synthetic if consistently towing near rated limits. Perhaps that is all that is needed. While I am towing near the rated limit I am mostly doing short, low speed trips and doubt that my axle gets that hot.

Food for thought, I don't think that I have ever seen a class 8 tractor with a finned cover.

Class 8 tractors usually don't have covers...the centersection comes out, like a 9" Ford.

[Jarlaxle]

GordonThree wrote:
If casting fins into the housing cover solved any problems, wouldn't the manufacturer be doing that already?

Not if it cost an extra thirty cents per unit...

[deltabravo]

agesilaus wrote:
For what they charge they better look nice, $200 for a couple of pounds of stamped aluminum is overly expensive IMO.

The ones I've seen aren't stamped aluminum, they are cast.

[Groover]

Cummins12V98 wrote:
"I was going to change my dif oil but the service manager just told me that synthetic is standard in newer Fords so don't worry about it."

I highly advise reconsidering that! How many miles are on your truck?

20,000. Yeah, I will probably change it before the 100,000 mile recommended interval. Especially if I get in any deep water. I have never had a differential fail but I have seen some manufacturing crud come out of new gear boxes so there is probably merit in doing it the next chance I get.

[dodge_guy]

Diff fluid is cheaper than repairing a rear axle. Not to say it will fail but preventative maintenance is a good thing.

I do my rear axle about every 30k miles. I do my trans every 25k.

[Cummins12V98]

"I was going to change my dif oil but the service manager just told me that synthetic is standard in newer Fords so don't worry about it."

I highly advise reconsidering that! How many miles are on your truck?

[Groover]

falconbrother wrote:
Due to this thread... When I got home last night from a day of pulling the camper (5800 dry say--6800 wet) I checked my differential. It was hot as a firecracker (technical term). Too hot to hold your hand on. Not that it matters I guess. It was working hard pulling through about 100 miles of low mountains. I just serviced it before the trip. I have a small-ish pinion seal leak. I will fix that in a few days.

I found this info on a different forum:
Eaton conducted tests on oil/component durability during the late 1980s early 1990s

Their intent was to maximise seal and gear life and to allow the maximum OCI possible for their Heavy Truck gearboxes and diffs when using 75w-90 and SAE50 gear oils

They found;
a) components should not be operated at consistent temperatures above 250F
b) Intermittent operations to 300F do not harm the components or oils (synthetics)
c) Oils with a sulphur/phosphorus additive package activate rapidly above 230F.
d) A poor additive package in a synthetic lubricant may not be as good as a good (thermally stable) additive package in a mineral oil

My experience is that synthetic gear oils (75w-90 and SAE50) usually reduce operating temps by from 10-20C

https://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=516393

It sounds like you can get firecraker hot to the touch without causing problems (other than burning your fingers) and generally synthetics can take a little higher temps than the mineral oil that is referenced above.

I was going to change my dif oil but the service manager just told me that synthetic is standard in newer Fords so don't worry about it.

[falconbrother]

Due to this thread... When I got home last night from a day of pulling the camper (5800 dry say--6800 wet) I checked my differential. It was hot as a firecracker (technical term). Too hot to hold your hand on. Not that it matters I guess. It was working hard pulling through about 100 miles of low mountains. I just serviced it before the trip. I have a small-ish pinion seal leak. I will fix that in a few days.