Questions about 9" rear axle - Ford Truck Enthusiasts Forums

Questions about 9" rear axle

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Old 08-26-2004, 12:46 PM
bbtkd bbtkd is offline
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Questions about 9" rear axle

Greetings - I have a 1973 Ranchero with a non-posi 9" rear axle. I recently put a 400 HP motor in it and in order to improve traction, I would like to go with a limited slip rear axle. I have no info on the current ratio since there is no tag on the axle and someone cleverly removed the door tag that would have told me. I should also mention that there is a sound in the rear axle - sounds like a dragging brake but it isn't. It is mostly heard when coasting at low speeds (probably since that is the only time it things are quiet enough). Since I have replaced the rest of the drivetrain and had the brakes redone (and checked) it's down to being in the axle.

What do I need to buy to swap to posi? How do I know how many splines my axle has? Should I just swap out the whole rear axle for one with posi, and rebuild it (mechanic told me that mixing axle parts can be a hassle to setup)? Or should I buy aftermarket parts? Thanks!
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Old 08-26-2004, 01:34 PM
85e150six4mtod 85e150six4mtod is offline
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Check out this link:

The 9 inch is the poor man's quick change. You have several ways to go.

When the time comes to pull the diff, you will learn lots when you pull the axle.

Big bearings or small, and 28 or 31 spline.

I'd guess you have a 3.00 or 3.25.

For limited slip, you can go with the Ford limited slip, which is the clutch pack deal, and which can be beefed up.

Or the Detroit Locker, which is strong but clanks and bangs and barks the tires around corners sometimes.

For either you have to rebuild your carrier (not for amatuers) or

--get lucky and buy one that doesn't howl

--buy one from someone who knows what they are doing. (Currie and others)

I paid about $450 for an open 3.50 about 10 years ago. Took them 5 diffs to get one that didn't whine.

These are easy enough to change so it depends on your tolerance of doing this more than once or parting with $500 to $700 or more.

Happy motoring!
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Old 08-26-2004, 01:56 PM
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ranchero77 ranchero77 is offline
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search this forum for "28 or 30 spline" that should be all you need. and you'll see that I pulled the axle anyway.

are you changing the gear ratio? if not I would just buy a new carrier and rebuild what you have. then you'll only need the 3rd member gasket, carrier bearings and some new gear oil as long as you don't find anything wrong when you get into it.

if you changing gears you can buy a 3rd member allready set up the way you want it.$$$ or if you have the time, know how and tools you can do it all youself.
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Old 08-26-2004, 09:58 PM
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Dealford Dealford is offline
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Some light reading from the Ranger board:
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Old 08-27-2004, 01:06 PM
grclark351 grclark351 is offline
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if your noise is an axle bearing, your in luck! Powertrax just came out with new products for the 9". all you'd have to do is reset the backlash after installing the Powertrax carrier parts. if after you replace the axle bearings and the noise is still there, the whole diff has to be redone. still a good time to install the Powertrax set-up. not cheap though, $430 at summit. PN PWT-92-0690-2800 or -3100 depending on the splines. a lot of people say the stock Ford Trac-loc doesn't last, i don't know about that but i wish i had the choice of the Powertrax when i did mine.
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Old 08-30-2004, 10:36 AM
rodbender rodbender is offline
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The axles would be 28 spline. Been there. I installed a 3.00 posi I puchased at a swap meet. To do it, you take off the wheels, drums.( Obviously it's on jack stands).Then you remove the four nuts on each side holding the retaining plate. You then slide the axles out(you may need a slide hammer & careful of the seals in the axle tube). Now they will clear the 3rd member for removal. remove drive shaft and the nuts holding the member to the housing( you might want to drain the fliud before this step). It's now ready to remove. Have fun . As a note I think the Powertrax is a cool set up as the posi units have unique pieces. The powertrax fits an open dif and replaces your spider gears.
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