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!
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.
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.
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.