8" posi third member install - Ford Muscle Forums : Ford Muscle Cars Tech Forum
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post #1 of 5 (permalink) Old 07-04-2009, 12:26 PM Thread Starter
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8" posi third member install

I have a 67 mustang Coupe with an open rearend in it. I recently found my self a posi 8" thirdmember a 3L00 in a 1976 mustang II. The price was right I only paid 260 for it. I am needing expert advice on how to clean up the member and install it in my car . I greatly appericate your help.

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post #2 of 5 (permalink) Old 07-06-2009, 09:14 AM
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Re: 8" posi third member install

Its not a big deal to change. Your axles need to come out about 12 inches or so, and then disconnect driveline, and start removing nuts that hold third member in. It's a pretty serious chunk of iron, so be prepared for the mess of the oil, and the weight of the diff. probably should let it drain for a spell before actually jerking it off the housing.
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post #3 of 5 (permalink) Old 07-06-2009, 09:16 AM
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Re: 8" posi third member install

I would hose it down with degreaser and then take it to the car wash to clean it up, inside and out. I'd dry with compressed air to get all the water out of the bearings.
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post #4 of 5 (permalink) Old 07-17-2009, 01:17 PM
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Re: 8" posi third member install

Most parts stores will rent you a puller for free once returned for the deposit. I'd pick one up before you start, the rear axles can be a bear to get loose some time. It looks like a slide hammer for pulling dents, a couple quick whacks and mine came sliding out. Reinstall took a few taps with a block of wood between the studs and a large rubber mallet and they snap back in.
Be sure to put a bottle of ford tracloc friction additive with the new oil.
Depending on what your planned use is, you may want to have the gears upgraded from 3.00 to 3.50:1, etc. at this time before install.

"If it isn't broke, I haven't fixed it yet" - Jon
'67 Coupe 289>333 AFR 165's, AOD, 9" 3.50:1, PDB
'09 Warriors in Pink w/glass roof - the wife's Mustang
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post #5 of 5 (permalink) Old 07-18-2009, 10:16 AM
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Re: 8" posi third member install

From what I take you already have it out of the diff. You can pull the pinion assembley, just don't loose the slims or change them and that'll help to clean it up. Personally I would take it to a good shop experience in rebuilding them and have them put all new bearings, races, and clutches. You never know what shape it's in right now and it could have trashed bearings. Maybe put some 3.25s or 3.55 gears in it too.
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