Hi All, a recent purchase...and I'm trying to identify what I've got... I was told a Ford posi...(not sure what that might mean to me) and for parts sake...how do I identify the year? or is that important? I was also "whining" about my gas mileage...(yes...I whine...mostly for my own amu*****t) and was told to see what my tire rotation to my drive line was...im getting about 3.5 turns per tire rotation...does that sound right? might someone tell me what that tells me thanks in advance...
It is either 3:50 or 3:55 Ratio. Mileage should not be bad at all. I have a 3:55 in the Divco, The 502 loves the, 3:55
That's the early Ford 9" 'round' housing (57-59). If it has a drain plug at the bottom, it's a 57-early 58. The plug disappeared in late 58, never to be seen again.... The pumpkin looks to be a bit newer, although it's hard to tell.
Why would they do that? I've heard that 9 inches are a bit overkill most of the time and have a good bit of drivetrain loss, which would cause bad gas mileage. But just something I heard from a kooky old guy at a car show. He also said sway bars were unnecessary. He seemed to know his way around a 9 inch though, at least the issue my friend was having with the brakes.
I remember a guy once telling me a 9" you cant get a socket on the bottom bolt but a 8" you can.looks like a 9"
They are a high hypoid design, almost a worm gear, which gets the driveshaft down low for a smaller floor hump. This means lots of tooth contact, which makes them strong, but also creates a lot of friction, which reduces mileage and generates heat. I don't think it's a big difference in efficiency, but enough to get replaced by the 8.8".
That guy gave you good information about a quick way to recognize the difference between an 8" and a 9" rear. The one in the photos above is an early one because it does have the drain at the bottom of the housing. It is a shame that Ford did away with that feature. It is real handy when changing center sections or gear lube.
I know...I wasn't thinking when I signed up...I think I may dump this username...and let "original" Sp. Ed alone... Sorry dude : /
When I set up a 9" I weld a bung on the low point of the housing and screw in a drain plug. Worth the time and trouble later.
You do have to be careful about mounting swaybars to some of the housings. If the bar is a frame mount (with only links to the spring pads), you'll be ok. The later housings used thinner material in the axle tubes, and if the bar mounts are much distance away from the spring pads you can get enough leverage to bend the housing. The ones to really watch are some of the late 60s/70s versions where the axle tubes 'neck down' to a smaller size between the center section and the springs. I had Morrison narrow one for a '70 Montego I had, and the Addco rear bar I installed kept bending the housing (leading to axle bearing failure). Took a while to figure that one out....
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