edwinsmith

I have a D350 dually. I think it is a Dana 70 real axle.

How does one go about draining the gear lube to change it? I don't find a drain plug in the bottom.

thrashingcows

Have to pull the rear diff cover....bit of a messy job but not too bad.

edwinsmith

Thanks. I found a video on the job so I need to go get a gasket. The video guy said I need some friction modifier and AmsOil something. Any ideas about that? I've never heard of that and always just used whatever the Jiffylube place puts in.

oliver foster

I just use RTV for the gasket. I let it cure over night after tightening down the bolts pretty snug. The next day I torque them down and fill it.
I just put a couple of bottles of a friction modifier that Napa sells into the Dana 80 with factory LSD when I put it into the Gorilla last winter.

bigragu

Edwin, no need for a gasket- just use black oil resistant RTV. Torque to spec after a certain amount of hours after install(field service manual describes procedure). Then, after that final torque, fill with gear oil. Here up north of you in Auburn, CA I run Lucas 80/90 and I use 8 ounces of friction modifier only because I have the mag- hytec diff cover which takes up 6 or 7 pints of lube. I follow the instructions on the Friction modifier container that explains the ratio per bottle to how much gear lube my diff will take. FM typically comes in 4oz. Containers at the auto parts houses.

Not having a two wheel drive, I always thought that FM were for axles with limited slip only, which my W250 has.

If your budget allows, slap on a Dana70 mag-hytec cover. It is designed with an O-ring seal, and has a drain plug along with a magnetized dipstick(fill port) that shows a line for the correct level of fluid, and the magnet acts as a filter by catching all floating metallic particles.

Draining of the diff will never ever be a messy job again from then on. You’ll never ever have to remove the cover. It actually becomes a labor of love, lol.

I bought mine thru Geno’s garage years ago.

GSP7

Use the proper Grey Gasket Maker.

edwinsmith

Thanks Augie:

Unfortunately I just paid bills and the bank account is low until the eagle poops again. If I have to pull the cover it isn't that big of a deal. The biggest problem is dropping the spare tire which I have to do anyway since it is flat.

I tried looking up my VIN online but the sites don't show any info on what type of diff I have. One seemed to show that ALL of that year had limited slip but I'm not sure. I took the little tag off the bolt on the diff and it says:

46-13
3.54

I'm guessing the 3.54 is the axle ratio but I have no clue what the other number is.

It looks like somebody previously used some red RTV looking compound on it before. The video I saw said to use a certain type that requires no gasket sealer at all.

Does anyone know what Diff I have or a good site to look up my VIN?

Thanks everyone.

Edwin

oliver foster

I bet if you divide 46 by 13 you end up with 3.54.
That would be the # of teeth on the ring to the # of teeth of the pinion.

Just jack up the truck and see if your wheels spin in the same direction to see if you have a LSD rear end.
Or you can wait till you are looking at it when the cover is pulled.

All trucks of that year having LSD is not true.

edwinsmith

Yep. 46/13 = 3.5384615385 so if you round up to the next hundredth...

So off to Oreilly's...

Jim Lane

Edwin,
46-13
is you ring gear/ pinion tooth count

3.54

I took my spare tire down several years ago when I replaced my shocks and stuck it beside my house, someday I will put it back to stop the carrier from ratteling.
It is a killer on duallys, not so bad on SRW's.

I have only had one flat/ blowout on my truck in 18 years and that was when I hit something on the I-57 freeway at 80 mph stayed in perfect control never even swerved.

Never had a need for the spare tire.

Do you have a class IV or V on your truck?
That makes it worse unless the carrier has been modified.

edwinsmith

Getting it down is not much of a problem. It's getting it back up there that's hard. The guy that put it up there had to balance the tire on his belly to lift it and get the funny nut started. then he had to take it down again to flip the wheel over (always a 50-50 deal). I could always throw it in the bed because I have the shell on. I have a class 3 hitch.

Losing a dual unloaded I could probably drive it in a low speed as long as the bad one didn't get tangled up some way. I've often wondered if a front blew could one pull the outside dual and put it on the front? Should the rear single on a dually hub be inside or outside?

Just my curioscopy.

NJTman

Edwin,
If you're using Amsoil severe gear fluid in there, you are not going to need the friction modifier, as Amsoil already puts it in there. I did not believe this until I called the, spoke to their tech support, and they confirmed. No issues, and no growling areound corners. I'd you have an open diff, not needed anyway.

I put 75w140 in there, I think, as it covers all ranges of environmental conditions I'll ever see.Gasket o
or goop, either is fine. Just don't put the oil in till the next day, as previously stated, allowing full cure of the goop.

thrashingcows

I have never waited more then a few hours on the RTV when doing a diff cover, and I have never had any leaks. I smear the RTV on the cover and let it sit for 10-15 min, then install the cover, snug the bolts up enough to hold it in place then let it sit for a few hours...then do the final tighten. Fill with fluid and go.

edwinsmith

That's probably the way I'll go. The RTV Gray was recommended above but I have some RTV black left over. Would it work as well?

I've decided to put it off for a week until the eagle poops again in case I run into complications. I just double checked and I bought too much gear oil. SO I can trade a gallon of it for the RTV.

Edwin

thrashingcows

I have used all kinds of automotive RTV, black, red, grey etc, some work better then others, but the Black would be fine IMO....I'm pretty frugal so I'd use it up myself.