The fill plug visible in the first pic posted by the OP is an aftermarket item, definitely not factory. Below is a similar unit sold by Strange Engineering. Most commonly used on drag cars (along with a drain plug) to ease swapping gear sets at the track.
As already mentioned, drain and refill 2.5 quarts and be done, it will be super close to the exact amount needed. That aftermarket fill is mounted up high and is actually also used to inspect the ring gear too. You have around 6 quarts right now . I like to use Lucas 85/140 non synthetic gear oil
Yes that plug is not factory. As stated before it's used alot in drag racing. The idea behind it is when it's installed it's usually mounted high like that and directly over the ring gear. It's made to do 2 things, 1-make refilling easier and 2- inspect the ring gear teeth for bad or broken teeth with the abuse they take in a drag car. I've seen people mount them to the top of the housings too, off to the sides etc. Kinda defeats the purpose of being able to check for ring gear wear and tear.... .
Usually a beam style torque wrench. Put it on the pinion nut and rotate the pinion and see how much deflection you get in the beam torque reading. .
I always hated taking a third member loose and having the oil gush evrywhere......then there is always some remaining in the housing that has to be sopped out. I always weld a drain plug in the bottom of the housing and use an oil pan plug in it. Makes draining much easier and drains it all. Only minor sopping after that. Then I add a vent up high that I can thread a fitting in to adapt a hose and maybe a vent filter. This particular housing has two things sticking out that I think are vents. One above the centerline and one below the centerline of the axles.
Early 60's full size Fords '63 and '64 Galaxies for sure. I'm sure there were others as well. Early 60's 8 inchers as well.
How can you measure pinion bearing inch pound pre load /rotational torque when you're also turning ring gear , axles etc . With a yoke wrench & breaker bar & alignment marks , you should be able to "feel" when its tight ?!
Correct "feel" is an experientially obtained skill. I could teach students how to read a mic in 15 or 20 minutes. How to make consistent, accurate measurements was a whole different ballgame.
your correct it isn’t just pinion bearing preload, it’s overall rotational torque, works just fine. I’ve done a lot of differentials and I can’t feel the difference between a few inch pounds of torque, apparently I’m doing all wrong by doing it the most accurate way….
Ekimneirbo.... Those aren't vents, those are welded on solid location lugs for the stock vehicle application rear anti-roll("sway") bar support brackets. Many times the Ford 9" vent will be the same bolt that holds the hard line to brake hose "T"-fitting distribution block to the housing. Especially if it was a truck or van housing. The bolt is hollow with a hose ****** on the top of it.
Thanks! I never looked at them very closely, just ***umed they were vents but wondered why they were in those locations. They seem to be stepped on the bottom so I thought they had an air p***age......just didn't look closely when it was apart. Doesn't appear to be any weld holding them in place though.
The lugs are spot welded on The high/low location difference is so the same single bracket flipped over works on either tube.
Remember it's in in.lbs. A couple of pieces of tape marking the high/low of the range makes it easier to read. Also the reading will "flash" high on initial rotation.
You made me curious, so before you posted the second response, I went out and cut one of them off............you were exactly right. You can see the little relief at the bottom edge. Thats what made me think it was some kind of vent...but it weren't.
This area is drilled and tapped for a NPT plug on other centres. A friend years ago had a smooth housing with no fill plug and a centre similar to yours. He removed an axle and filled down the tube. A PITA, I suggested that he drill and tap casting. Another friend had a vent put in his 9" housing. It was drilled and tapped whilst ***embled however all the swarf was allowed to drop down into the housing Needless to say rear axle had to be stripped down and cleaned out.
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