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How to Drain Differential Oil?
#1
Hi guys,

I would like to change the rear end oil on my 1972 9". I do not want to pull the pumpkin and axles out to do this if I can avoid it. I have read many posts on how people say just get a hand vacuum pump and suction out through the fill hole...well I have tried this but am not able to get the hose inserted through the fill hole as it immediately hits the internal gears. Is there something I am missing here??

Many thanks...

Jeff
1972 Q Code Convertible
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#2
Hand vac pump is how I originally did mine. Not the best for sure as I know your don't get all the oil or other crap out and it takes a while. I had to use a pretty small diameter vinyl tube and it took some finagling to get it past the gear and down in. When I swapped out my gears I used a lube-locker gasket as it is reusable so now I loosen bolts and just pop it a bit with a dead blow hammer to break the seal to let it drain out the bottom and then torque it back on and refill.

'73 Grandé H Code. Headman long tube headers, T-5 Transmission, 3.70 Traclok, Lowered 1" all around, Aussie 2v heads w/ 2.19 intake, 1.71 exhaust, screw in studs, full roller cam 608/612 lift 280/281 duration LSA 112, Quick Fuel 750 CFM double pumper, AirGap intake.

'73 F code convertible. Bright red. Needs total restore. (IE HOT MESS)

- Jason
[+] 1 user Likes 73pony's post
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#3
I would try a smaller tube, see if you can get it into the bottom of the housing. If not, I would try removing the bottom stud from the carrier, I believe that it goes all the way through the flange, into the housing (I could be wrong, a long time since I pulled one).

If you still can't get it drained, pull the pinion retainer/support as one unit. You should be able to get a drain hose in from there. If you go this route, it's critical that everything is spotless when it goes back together, one piece of grit on the shims will mess up the pinion depth adjustment. I would plan on having to replace the o-ring. They only cost 3 or 4 dollars, plus shipping, from a variety of sources.

Whichever way you go, I would also try to get a magnet on a flexible shaft into the bottom of the housing to get any metallic sludge out.

I know that people have also drilled and tapped the bottom of the housing for a pipe plug, but I'm not in favor of it, unless the plug is the kind that has a socket for an Allen wrench, and the plug is flush with the housing. Wouldn't take much to rip it off if it stuck out. Others have welded a bung on the bottom for a drain plug, but I also wouldn't want one of them protruding either.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#4
runninpony 
Pulling the axles isn't that much of a big deal, while you're there you can check wheel bearings as well. You can borrow the needed tools from your auto parts store.

71-73 Mustangs never die, they just go faster!
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#5
Use a piece of brake line that's a snug fit in the end of your pump hose, and bend a "U" shape into it. Get out what you can, refill and call it a day.


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#6
If you can get a smaller tube into the housing it will help to suck it out if the housing is warmed up, especially if it isn't synthetic lube.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#7
Me I always put the car on jack stands and pull the two axles in about 15 min. While apart replace the rear axle grease seals and check the bearings. You should not need a puller for the axles.
If you punish your car with burn outs. You can put tape on the clean axle and paint a white stripe on it. That way the next time you pull them you can tell if they are twisting. Be sure and get new gaskets for the axle flanges also.
With the axles out you can take the third member out and wash all the crud out of gears and also the housing. I would make me a swab to run inside the axle tubes to make sure you get all the crud out.
New gasket with some Black RTV on the housing and gasket and go back in. If you have limited slip be sure to get a bottle of the friction modifier to add to the rear grease to prevent damage.
If it has never been changed you will be amazed at all the metal inside the rear from wear.
Might be good time to put new shoes on the rear also.
If you do not have grease fittings on your U joints take them apart and grease while the drive shaft is out.
The rear grease has that fragrant fresh spring time smell also, lol.


When a man is in the woods and talks and no women are there is he still wrong??
Tongue
David
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