Replaced Rear Differential Cover and Fluid

Jim-n-Leslie

Active Member
I spent today cleaning up my rear differential on my F350 SuperDuty Lariat Crew Cab. I couldn't be more pleased with the results. I bought the Mag-HyTec cover, six quarters of Royal Purple (75W-90), rolled up my sleeves, and headed under the truck. As the photos show, the old cover was quite rusty. It would not take much to punch a hole through the old cover. I pried it off, I sopped out the old oil, cleaned up the mating surfaces with wet-n-dry cloth from the auto store, cleaned everything up with solvent, and closed it up. Torque'd down all of the bolts to spec. The original was supposed to have 3.4 quarts of oil. It had two. The new one takes up to six quarts, but five brought it half way between the hi and lo marks. I drove it a bit to see how it felt. It does have some slip (being a limited slip differential), so I will add the additive tomorrow and check the oil level. Next weekend I will do the front differential. I got a Mag-HyTec for that as well, and four quarts of Royal Purple. Besides looking great, this should do well for keeping the towing/hauling temps down and ensure plenty of lubrication through the upcoming summer months. I can't wait for our first camping trip! :cool:
 

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Paul_in_MN

Active Member
Is the Royal Purple a synthetic hypoid lube? I know it is a respectable brand. But as I recall my F350 owner's manual requires a full synthetic axle lube. The synthetic is able to withstand heat better than non-syn GL5. IIRC, my Ford manual calls for change at 100,000 miles.

I really doubt your cover was about to rust through. I am still running an 86 snowplow truck with SERIOUS rust, on which many brake lines, fuel lines, and even the engine oil pan has rusted through, but neither axle cover has leaked or seeped. And both are hitting hard snow and ice constantly. Everything on the bottomside of that truck has rust blisters the size of barnacles, including the driveshafts and axle tubes. It is not my RV or pleasure truck.

Thanks for the pictures and the reminder that we all need to consider this maintenance task. Which brings up another maintenance question...do we have to change out the gear oil in the 4wd transfer case, or does it swap oil with the auto tranny?

Paul_in_MN
 

RollingHome

Well-known member
Jim, Thanks for sharing :) Keep us posted on your results, besides looking good, this may be a desirable upgrade for others. I'm toying with the idea of monitoring differential temp. Sure would be insteresting to record before and after temperature results, that cast aluminum cover would make it easy to tap a threaded sensor hole. I'm not at all familiar with the Royal Purple, is it better then Amsoil synthetic - in your opinion.
 

westxsrt10

Perfict Senior Member
I spent today cleaning up my rear differential on my F350 SuperDuty Lariat Crew Cab. I couldn't be more pleased with the results. I bought the Mag-HyTec cover, six quarters of Royal Purple (75W-90), rolled up my sleeves, and headed under the truck. As the photos show, the old cover was quite rusty. It would not take much to punch a hole through the old cover. I pried it off, I sopped out the old oil, cleaned up the mating surfaces with wet-n-dry cloth from the auto store, cleaned everything up with solvent, and closed it up. Torque'd down all of the bolts to spec. The original was supposed to have 3.4 quarts of oil. It had two. The new one takes up to six quarts, but five brought it half way between the hi and lo marks. I drove it a bit to see how it felt. It does have some slip (being a limited slip differential), so I will add the additive tomorrow and check the oil level. Next weekend I will do the front differential. I got a Mag-HyTec for that as well, and four quarts of Royal Purple. Besides looking great, this should do well for keeping the towing/hauling temps down and ensure plenty of lubrication through the upcoming summer months. I can't wait for our first camping trip! :cool:

I have the same cover as you (great products)....the Royal Purple has the slip additive in it, too much additive will cause slipping and damage the clutch plates. The correct lube for your axle is 85-140, part #01303.

I have a new 08+ Mag-Hytec transmission pan going up for sale on Ebay soon, its 7.5 qt over stock but won't fit my V-10 because of exhaust Cat clearances.
 

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Jim-n-Leslie

Active Member
I went back and forth on the oil weight to use, and finally went with the advice of the local Ford heavy truck service at the local dealership. Before I spend a small fortune to replace the Royal Purple I went with, are there pros/cons with staying with what I have? I still have the front differential cover to replace, and I have 4 quarts of the same weight oil for that project. I was hoping to tackle that tomorrow.
 

Jim-n-Leslie

Active Member
Sorry about taking so long to get back to you. I've been out of town. I probably did exaggerate a bit on the corrosion, although it did have quite a bit of corrosion with flakes falling off the face. I took a look at the inside surface and it was fairly clean. The oil I drained from it was fairly clean as well. You asked if "Royal Purple a synthetic hypoid lube." The way they describe their product, they say "All viscosities of Max-Gear are formulated with hypoid friction modifiers necessary for use in clutch or cone type differentials. No additional additives are necessary." As far as the 4wd transfer case, I am no expert on that piece, but from what I can tell, it is isolated and unable to transfer any oil. It has to be changed as well.
Jim
 

Jim-n-Leslie

Active Member
So far it rides well. I have a front cover the change out. I was looking at including the temp monitoring capability, but decided the cost, on top of everything else, would have to wait. Aside from hauling 6-7 tons of trailer, I do not put a much heavier demand on the truck. I figure this will keep the temps under control, given the added volume of oil, the heat transfer fins on the aluminum body, and the Royal Purple synthetic I used. As far as Royal Purple goes, I have heard great things about it, above and beyond Amsoil, which is a respectable brand of synthetic. I decided to go with the iol that seemed to have the most "votes." For my engine oil, I went with Shell Rotella T because after running through a number of diesel truck forums, it seemed to be the highest rated synthetic for engine oil. At the time (Nov-Dec 2009), Shell had just announced Rotella T6 and the specs on that exceeded Rotella T. I checked a number of truck stops and Shell stations on a road trip back in early December and could not find T6. I knew they sold Rotella T at WalMart, so in the end I bought 15 Qts of Rotella T. Today I was in WalMart (I practically live there, but only because it is just around the corner form the house) and noticed that they now have Rotella T6 on the shelf. When I am due to change the engine oil this summer, I am planning on moving over to T6, unless something is posted in the forums indicating it is a bad idea - which I do not expect to see.
Jim
 

jbeletti

Well-known member
Wish I could put a nice mod like that on mine but the experts here say I can't - not on that big fat Dana on mine. Got a sealed pumpkin I guess. Speaking of rusty - the and axle as well as a few other components under my truck are rusting terribly. Flaking etc. Time to get under it and wire-brush/POR/prime/paint it I guess. Yeah - that will never get done!

Anyway - nice job on yours Jim.

Jim
 

westxsrt10

Perfict Senior Member
That oil is fine for the front axle Dana 60...in fact it calls for its use there. I bet you have the Sterling 10.25" in the rear, it calls for Syn 85w-140. Beware and note that Mag-hytec raised fill level over the stock spot so to avoid issues don't fill it MAX in the stick. Their LO mark is still 1" above the factory stock level. (something about foaming or getting too much air in the oil)
Their trans pan won't fit my truck (they sware they fit a V-10 with it) I have the exhaust dropped down 1 1/2" in the photos.
 

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Jim-n-Leslie

Active Member
Thanks! I did see where others filled at or above the hi level mark and ended up with foaming. I brought it a bit over the lo mark on the back. I will watch the front when I do it tomorrow. I will have to monitor the rear oil and plan on changing out the rear oil this summer if necessary. I hate to have wasted those 6 quarts. How significant an issue is what I used versus the Syn 85-w140? Should I be panicking and change it sooner? Good photos. That is a tight fit with that exhaust! I was considering the oil pan for the future, maybe this summer or fall.
Jim
 

porthole

Retired
Jim, Thanks for sharing :)
I'm toying with the idea of monitoring differential temp. Sure would be interesting to record before and after temperature results, that cast aluminum cover would make it easy to tap a threaded sensor hole. I'm not at all familiar with the Royal Purple, is it better then Amsoil synthetic - in your opinion.

The Mag HyTec covers are temp sensor ready. The top of the cover is drilled, tapped and plugged for your convenience.

I used Royal Purple in the past but after reading an in depth synthetic oil study I now limit my oils to Mobile 1, Amsoil or Red Line.


Thanks! I did see where others filled at or above the hi level mark and ended up with foaming. I brought it a bit over the lo mark on the back. I will watch the front when I do it tomorrow. I will have to monitor the rear oil and plan on changing out the rear oil this summer if necessary. I hate to have wasted those 6 quarts. How significant an issue is what I used versus the Syn 85-w140? Should I be panicking and change it sooner? Good photos. That is a tight fit with that exhaust! I was considering the oil pan for the future, maybe this summer or fall.
Jim

I would just keep the oil you already have.
 
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RollingHome

Well-known member
Jim x 2,

If you think your undercarriage is too rusty check out a Ziebart dealer in your area. They treat your undercarriage with their propietary "stuff" and guarentee it against rusting. They also will touch up any spots if needed later. I checked on this in Oct 2009 the Maryland dealer wanted about $250.00 if memory serves me right. Most Ziebart dealers also install Rhino spray in liners too. You could kill 2 birds with one stone.
 

NewCyclone

Active Member
Here is a comparative study that AMSOIL had completed on Gear Lubes for everyone's reading enjoyment. Study is attached.

I really like that diff cover by the way and will be doing mine in the future!!
 

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SouthernNights

Past South Carolina Chapter Leader
Thanks for posting that study. I think it is interesting that Amsoil's score was almost half of the second place oil and if had done a little better in the price category it probably could have been half.

While I have always been an Amsoil fan-not necessarily a user though-I find it interesting that alot of the test was done in house at Amsoil if I am reading the "Method" section correctly.
Not really sure if that is a point or a non-concern looking at the tests results.
Either way, I am glad you shared that.
 
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