I'm fixing to hit 15000 miles on my truck and I'm gonna do the axle fluid changes myself. Should I go with the recommended fluid in the owners manual or have others had better luck with other weights? Also, what is a good brand to buy? Last question, I was thinking of going with a mag hytec differential cover, are these things worth the cost? thanks for the help

 

I don't know if the MH is worth the cost, but it sure does look good on there. I get compliments all the time..........or questions from unknowing gasser drivers. It is also nice to look at the MH "dipstick" occasionally and see what the fluid looks like and clean off the magnet. You can also drain the fluid from a drain hole instead of just letting it run out like when you pull the stock pan.....which has no drain hole.

I went with Mobil 1 75w/90 and it seems to work great. If you pull heavy you might consider 75w/140.

 

I went redline 75-140 on the advice of my dealer. (It's often 110 or above here in the summer, and I tow).

 

When are you supposed to change the fluid? I've never changed differential fluid in any of my trucks until I hit 100k. Are these differentials any different? I'm sitting just below 70k on this truck and I haven't changed it. Am I doomed for failure??

 

I plan to change it out every 15k (i only have 22600 so far with one change out) which is what the owner's manual states. I agree that that may be a little often, but I figure it doesn't hurt......and can only help.........and it isn't that expensive considering the cost of our trucks.

schorb, I don't think you are doomed to failure ....but I think I would put that on my to do list pretty quickly.

 

From what I've read, the first gear oil change is the most important. You remove the wearing-in material and any foriegn bodies, from casting, etc. From my experience, I would recommend an early, first change.

The first change (15,000 miles), the gear oil looked grey and dirty with a little metal residue. The grey comes from the assembly lube & milling-in compound, I've heard.

The second change (37,000 miles) showed a cleaner but, darker colored oil.

At the first change, I installed a Mag Hytec rear-end cover. I pull a 7000 lb. trailer, sometimes across country, and wanted the fluid to be cooler. One of the things you should know about the MH is that it raises the level of the gear oil, rather dramatically. The MH recommended level puts the fluid into the axle tubes up to the bottom of the axles. It will keep your outer bearings in a "bath" of gear oil.

I called MH about this and their response was that it is better for the rear axle and won't cause any problems and that thew had sold over 30,000 of these units without any problems.

The other argument is that too much fluid will cause "foaming" or entrapment of air in the oil. Air does not make a good lubricant.

The MH has a dipstick which has a top line putting the fluid at the bottom of the axle, and a bottom line which places the fluid at the bottom of the axle tube. If you want to maintain the factory recommended level, they have put a "plug" in the identification plate which will give you the factory level.

Another argument against the MH is that the black powder coating acts as an insulator and doesn't allow the unit to cool the fluid as well as if it wasn't there.

There is another product on the market called a PML cover (I believe). It does not have the powder coating, just bare aluminum, keeps the stock, factory fluid level, & is cheaper. Just something else to consider.

BTW, I never had any problems with my MH. Never leaked, anywhere. The gears showed no signs of excessive wear or wear patterns that might be associated with entrapped air. And, I like the looks of it.

The first gear oil change, I used the factory recommended fluid. Very expensive!!! $21.00/ quart but, I got them down to a little over $15.00/ quart. I was told this product is made for DC by Texaco. This last change, I went with RedLine 75w-90. From the reading I've done on bob is the oil guy.com website, RedLine products are very well thought of. Their synthetic base stocks are of very high quality & the additives are also superior.

If you have too much time on your hands, and are curious about the different lubes available, the bob is the oil guy.com website has an incredible amount of information. I've learned alot. There are very high quality lubes, out there, that I have never heard of.

If you shop around, you can get great prices on high quality lubes. I found the RedLine for $7.00/ quart at my oil shop.com. Went to the local distributor and they matched the price. Elsewhere, they wanted $9.15/ quart.

For those of you with the NV-5600 (6-speed) trans., I tried a transmission gear oil called MTL-P from Specialty Formulations, in El Dora, KS. These people build extremely high quality lubes. Those of you with the NV-5600 know how "notchy" the shifting is in these transmissions. They are a big, heavy-duty, slow shifting trans. The MTL-P gave mine a slight improvement in the upshifting & downshifting quality. No dramatic difference but, never the less, an improvement over the stock fill and the Pennzoil Syncromesh at the 15,000 mile change. I have very few miles (13) on the MTL-P and notice the shift quality keeps improving. Don't know when or where it will level out.

Well, this is my story & I'm sticking to it.

Joe F.(Buffalo)

 

Are there any writeups anywhere on how to do this the right way? Will I need to get another gasket for the front and rear?

 

Both front and rear cover gaskets are rubber and designed to be reused.

Just put a pan under it and remove the cover.

24 ft lbs fill hole plug, 30 ft lbs cover bolts.

 

I had a Mag-Hytec for my rear but it appeared that they were never going to get one for the front so I switched to the PML covers front and rear. PML's original front cover was recalled due to mechanical parts rubbing but have now corrected that problem and the new one is perfect. You can get PML's covers powder coated, plain or polished. As far as powder coating causing heat to build up the OEM cover is black which will do the same. If you've ever changed your front differential lube you'll be elated with a drain plug after you twist, turn, and contort your body and arm trying to torque you bolts. In addition if you don't do your own fluid changes you're crazy. I don't do my transmission but everything else. Called dealer to do my 60,000 mile service on my tranny and they quoted a price of $705.00 which turned out to be front and rear differential lube, transfer box and fuel filter, along with transmission. The transmission service only cost me $143.00 so figure that I saved $562.00 by doing the other service.

 

P.S. PML can use original gaskets.

 

Anyone a dealer for PML or where do I find them?

 

Order direct from manfacturer on their Web site. Good people to deal with. http://www.yourcovers.com/newdifferential.htm

 

Looks like I'll try and go with a PML cover for the back and 75-140 redline gear oil.
I'll go with 75-90 redline in the front. Does anyone know the part numbers for the PML covers for these axles?

 

P/N 10361 for the AAM 11.5 Axle and you need to specify finish.

 

Check my photo gallery for pics of the PML cover on my truck.

MikeyB