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The bearings on one of the axles finally gave out on my 72 Ranchero, and I'm questioning whether I should just replace what's broken, rebuild the rearend completely, or replace it with the 72 9" I have sitting on the side of the house. The spare 9" I believe came out of a F100 pickup, so the mounting brackets will have to be switched, but the length should be the same as mine. The reason I'm thinking of replacing the rearend is because the Ranchero has 88,000 original miles on it, and 4,000 of that has only been put on in the last 5 or so years. I figure that's why the bearings gave, they probably dried up from not much use.

I haven't crawled under the ranchero, so I'm not certain if it's an 8" or 9", I do know it's a limited slip diff. with probably 3:25:1 gearing.

The spare 9" is a posi, with 4:11:1 gears and in descent shape. I would prefer gearing around 3:50:1, but figure I could replace those later.

I don't have a welder, or weld for that fact (will learn soon), so I will have to have the brackets switched and welded (I'm hoping Pat can line me up with a good welder in town). Is there any down side to what I'm considering? or should I just replace the axle bearings, and hope I have no other problems with the existing rear?

Doug

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If you DO decide to replace it, and the old one is a 8" Trac-Lok, let me know if you want to part with the center section.

'66 A-code Fastback (therapy)
'89 Town Car (SWMBO D'driver)
'87 Caprice (as req'd by Hagerty)
 

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I'm not to up on Trac-Loc and such with rears, One of my weak points I really need to work on. I know what a 8", 9", posi and limited slip is, and how to check gear ratios. How do you determine what exactly it is that you have, like Trac-Loc, etc.? Besides crawling under and finding the numbers on the casing.

Doug

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Jack up the rear end and spin one tire... If the other tire turns the same direction, its a trac-loc, if it spins the opposite direction, its an open... Or go do a burnout /forums/images/icons/wink.gif, 2 patches you have a trac-loc. If its a 9" housing, you can't use a socket+rachet on the bottom couple chunk bolts, you have to use a boxed in, so if a rachet fits its an 8 ". Good luck!

-Jason

'72 Mach 1 || '90 Talon TSi AWD
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O.K. so Open is just another name for limited slip, and Trac-Loc is just another name for Posi. /forums/images/icons/smile.gif

Doug

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Hey mr. posi traction loc open man....*G*

Why not just replace the wheel bearings?

No biggie...

Pop the axles out and take them to a shop or, if you have some friends at the city corp yard, have them do the press work for you...they've got all the stuff...

I'd do em but you can't afford me... I might be persuaded to horse trade the labor for a Z bar of known vintage in good condition...*G*

Measure your Bolt Circle on the truck axles.....that might be the deal breaker although nothing is impossible with the right machine tools....hehehe

Get back to us with what you find on the Ranchero rear and we'll proceed from there.....

Pat
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If you pull the old chunk out, you can divide the gear teeth to get the ratio. Simply count the number of teeth on the ring gear (big one) and divide by the number of teeth on the pinion (small gear). Worked perfectly for me on the 2.80 I had in my rear, even though I had trouble with the "spin the wheel" method.
As for the switch, I see no reason not to upgrade to the 9" other than to avoid the hassle. Considering that it's not a huge amount of time or money to pull your axles and replace the bearings, that may be your easiest solution.
As you likely know, the primary reasons for upgrading to a 9" is when your engine make 300+ hp (popular opinion?). The reason to change gears is to make them match your wants for using your car's power (top speed or off the line gearing).
I did not know anything about this before the VMF - I'm sure others with more first hand experience can be more specific / helpful than I - Dickson

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This is an easy one. Just replace the axle bearing. The second choice would be a rebuild of the chunk. Swapping entire rear assemblies of questionable compatibility is Russian Roulette with an automatic.
Good Luck

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