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Differential Fluid change out

crazedyak

crazedyak

That Guy
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Not my pics, or write up. Found it somewhere else, and thought I would post here for those like me who have not done this before.


I know everyone here probably knows how to do this but just in case I thought I would post it up anyways. It can be deleted if it's not wanted.

Ok we'll start with the axle's:

Rear GM 10 bolt

OlBlue016.jpg


Front GM 10 bolt

OlBlue015.jpg


The bolts around the differential are 1/2". Starting with the bottom screws go around the cover till the oil starts to run out. I would take all of them out but the top one, leave it for last. Then go ahead and take the cover off. This is what you should see inside.

Rear

OlBlue017.jpg


Front

OlBlue019.jpg


Let it drain for a bit and take a rag and clean the cover along with the what you can of the insides. Make sure you clean around the seal really well. I took a wire brush to it. Check for any metal shavings or for worn out gears. Here is what the fluid will look like. Mine had some water in the front end so it's a little more milky.

OlBlue020.jpg


Put on the gasket or use some liquid gasket stuff. Bolt back up the differential cover. For the rear end to refill you will need a 3/8" drive breaking bar to fit inside this bolt.

OlBlue018.jpg


For the front you will need a 5/8" wrench to take out this bolt.

OlBlue015.jpg


Each axle will take about 2.5 quarts of 80w-90 gear oil. You can put in whatever brand you want. But put the bolts back in and your ready to go!
 
I change the fluid in all parts of my 250 after every hunting season. But I drive in a lot of water.
My nonhunting vehicles get changed every 10K or yearly depending mileage. I know its overkill, especially with synthetics, but I expect 200K out of the hard parts on my vehicles.

Having said that, I suspect that your help is superfluous here. I don't think the covers stay on these trucks around here long enough for the oil to get dirty........
 
While your at it do yourself a favor and pick up a lube locker gasket. You'll appreciate it the next time you drop the cover and don't have to scrape gasket/rtv.
 
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I also use brake cleaner(1 can per diff) to rinse everything clean. Just make sure you let everything dry out really well before reinstalling the cover and refilling the diff...
 
he didnt say,but i always fill til it starts to dribble out the drain plug.that way you know it is full.
 
chulisohombre said:
he didnt say,but i always fill til it starts to dribble out the drain plug.that way you know it is full.
Click to expand...

I also jack up the passenger side tire a little when refilling. It lets me get a whole gallon in the 14 bolt. I put extra in since my pinion is turned up for a CV shaft to make sure the pinion bearings get oil.

The only downside to this is a little extra windage on the gear (you'll never know it) and if you have leaky seals, this will find em fo sho.
 
So what fluid do you use and do you use permatex black or a different type of gasket?
 
I run mobile 1 75-90 and a fel pro gasket with high tack red gasket sealer on each side.

I am sure others have used other products.
 
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I figure all my fluids are fresh except the front and rear differential. So, probably a good idea to get some fresh fluid in there. Gasket with sealer? I’ve read people just using “right stuff” or “black” permatex. I guess everyone will have their preference.


Synthetic or regular oil? How many quarts to do front and back? Seems this oil is sold by the quart.

Thanks.
 
TJ1978 said:
I figure all my fluids are fresh except the front and rear differential. So, probably a good idea to get some fresh fluid in there. Gasket with sealer? I’ve read people just using “right stuff” or “black” permatex. I guess everyone will have their preference.

Thanks.
Click to expand...
I use the red permatex high tack. Stuff because it's keeps the gasket in place.
 
I just use black silicone for the seal and the amount of oil depends on the diff. I also use 75w90 synthetic. It stayed cooler and lasts twice as long as standard fluid. Most diffs take 2-3 quarts each to fill up.
 
I know to fill until over flow. Since this stuff only seems be sold by the quart except that Lucas gallon. I was wondering many many quarts to by. I have 3/4 ton 8 bolt.
 
they make a specific sealer in a tube now for the synthetic oils of diff's .

and if you get the 1 gal or bigger you better have a way to pump it in the diff .

i use reg old valvoline in the qrt or mobile 1 if synthetic required . this way you get the nipple and can add a hose to it .

lots of synthetic specs say below the fill hole and DO NOT fill to hole level .
 
sweetk30 said:
they make a specific sealer in a tube now for the synthetic oils of diff's .

and if you get the 1 gal or bigger you better have a way to pump it in the diff .

i use reg old valvoline in the qrt or mobile 1 if synthetic required . this way you get the nipple and can add a hose to it .
Click to expand...


I have a pump I got to fill the Tcase. But I’ll just buy a few quarts with the nipple. Is synthetic required?
 
chulisohombre said:
I just use black silicone for the seal and the amount of oil depends on the diff. I also use 75w90 synthetic. It stayed cooler and lasts twice as long as standard fluid. Most diffs take 2-3 quarts each to fill up.
Click to expand...
I've used regular old rtv if I was in a pinch. But I try to get a gasket if time allows.
 
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