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Old 05-26-2009, 07:23 AM   #1 (permalink)
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Convert an 8 inch open 3rd mbr to a posi?

I have an 8 inch open 3rd member with a 3.55 gear and would like to know if a posi unit will fit in the same 3rd member case or is there a difference? Thanks for any info.
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Old 05-26-2009, 07:44 AM   #2 (permalink)
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Re: Convert an 8 inch open 3rd mbr to a posi?

I put a Tru-trac in my 8 inch carrier, no problems. You can also go with a Trac Loc if you want. They make both for the Ford 8 inch.
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Old 05-26-2009, 10:01 AM   #3 (permalink)
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Re: Convert an 8 inch open 3rd mbr to a posi?

I put a Detroit Truetrac in my Bronco's 8.8 rearend and couldn't be happier with it. Highy recommend it, There are some videos on Youtube showing the effects of a Truetrac-
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Old 05-26-2009, 10:13 AM   #4 (permalink)
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Re: Convert an 8 inch open 3rd mbr to a posi?

"67Coup" I assume you started with an open carrier right? So you are saying I can buy a trac-loc unit and it will fit my current open carrier? Did you buy new races, bearings, ring gear bolts, etc.?
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Old 05-26-2009, 11:56 AM   #5 (permalink)
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Re: Convert an 8 inch open 3rd mbr to a posi?

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Originally Posted by ishelz View Post
"67Coup" I assume you started with an open carrier right? So you are saying I can buy a trac-loc unit and it will fit my current open carrier? Did you buy new races, bearings, ring gear bolts, etc.?
Some of them will - ones that replace the spider gears should fit an open carrier. Otherwise, you will be re-mounting your ring gear on a new carrier. If the rear is well used, a kit with fresh Timkin bearings, etc is recommended.
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Old 05-26-2009, 09:40 PM   #6 (permalink)
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Re: Convert an 8 inch open 3rd mbr to a posi?

Checkout this link.

FORD 8" EIGHT INCH REAR TRAC-LOC POSI SAFE TO 550hp 9:eBay Motors (item 330331843315 end time May-29-09 21:03:33 PDT)
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Old 05-27-2009, 07:04 AM   #7 (permalink)
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Re: Convert an 8 inch open 3rd mbr to a posi?

I wouldn't give $800 for that. The "extra rib" case is not any stronger than any other. $180 for gears, $90 for rebuild parts - leaves $530 for labor and a trac-loc. I'd keep shopping.
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Old 05-27-2009, 08:12 AM   #8 (permalink)
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Re: Convert an 8 inch open 3rd mbr to a posi?

Thanks for all the info. I was just wanting to know if a posit unit will fit in the 8 inch open case I currently have and sounds like it will. I found a new posi unit, races, bearings and ring gear bolts on ebay for $350 with free shipping. They will press on the races and bearings so think I will tackle this one myself.
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Old 05-27-2009, 10:46 AM   #9 (permalink)
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Re: Convert an 8 inch open 3rd mbr to a posi?

Ive been looking for a reasonably priced unit for years and ever since the 8 in became "popular" prices have been going up.
The "tru trac" unit is around $450 the trac loc about the same and then you have to get it installed and dialed in.

From what ive been able to tell, to buy a completed case that has everything you need, (Ie; tru trac, trac loc, detroit locker, etc) your going to pay upwards of 700 for a complete ready to go unit.

One of 2 items that i would probably consider ( because of my cheap nature lol! ) is the "lock right" unit from richmond. It will install inside your open carrier and give you the "locked" setup without having to have everything dialed in. So you save in the labor part by not having to give someone near $250 to setup the carrier assy.
The other is the Powertrax from richmond as well.
its the same style of unit however slightly smoother "ratcheting" action. Reportedly. Also uses your current carrie and doesnt require professional assembly.
Neither one of these units are Race units for high HP and slicks, so use your best judgement. If your in need of that kind of unit be prepared to shell out the big bucks.
Here are some links
Lockright
Powertrax
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Old 05-27-2009, 10:57 AM   #10 (permalink)
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Re: Convert an 8 inch open 3rd mbr to a posi?

Quote:
Originally Posted by ishelz View Post
Thanks for all the info. I was just wanting to know if a posit unit will fit in the 8 inch open case I currently have and sounds like it will. I found a new posi unit, races, bearings and ring gear bolts on ebay for $350 with free shipping. They will press on the races and bearings so think I will tackle this one myself.

Don't forget that you need some special tools like a dial indicator/mag-base and the skills patience to set your ring and pinion up on the new carrier.
Ive been a Machinist for 18+ years and i tell you Ive built my own engines, and just recently (4years ago lol) rebuilt my C4 trans. But rear ends are a special deal. Knowing that you have the backlash, mesh, float AND the bearing lash all just right is a tough one. Also don't forget that you need some MAJOR torque to tighten the crush collar on the pinion gear. Then you have to get the tension just right. If all the above isn't done right you'll have a noisy rear and you'll wear out your ring n pinion out fast.
If you have the place and time to do it i say get all the right parts, tools , and a manual and tackle it. But don't expect it to just drop in and go.
For me when i decide to do my peg-leg Pinto 8 in Rear ill either find a great deal for a completed assy. (yeah right) or do it myself with a powertrax or lock right setup.

Good luck and let us know how it goes!
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Old 05-28-2009, 09:12 PM   #11 (permalink)
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Re: Convert an 8 inch open 3rd mbr to a posi?

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Originally Posted by ckelly View Post
I wouldn't give $800 for that. The "extra rib" case is not any stronger than any other. $180 for gears, $90 for rebuild parts - leaves $530 for labor and a trac-loc. I'd keep shopping.
That's my plan. I've already got the 3.80 gears a PowerTrax unit.

$450 for the PowerTrax
$180 for gears
$90 for the complete rebuild kit
$20 for a mag base dial indicator

$740 with me doing the labor.

Do you really think the "extra rib" case is not any stronger? Is this from experience? I was going to pick one up at a local Mustang wrecking yard. $150 for a complete used 67-up 8" extra ribbed case. Not worth it you think? Isn't it the case that breaks under severe loading?

Like with slicks. I remember you had some experience with the 8", but don't remember exactly what your results were.
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Old 05-28-2009, 09:51 PM   #12 (permalink)
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Re: Convert an 8 inch open 3rd mbr to a posi?

Quote:
Originally Posted by cccdjb View Post
That's my plan. I've already got the 3.80 gears a PowerTrax unit.

$450 for the PowerTrax
$180 for gears
$90 for the complete rebuild kit
$20 for a mag base dial indicator

$740 with me doing the labor.

Do you really think the "extra rib" case is not any stronger? Is this from experience? I was going to pick one up at a local Mustang wrecking yard. $150 for a complete used 67-up 8" extra ribbed case. Not worth it you think? Isn't it the case that breaks under severe loading?

Like with slicks. I remember you had some experience with the 8", but don't remember exactly what your results were.
Unfortunately they crack at the pinion support inside. At least the photos Ive seen and the stories Ive heard.
You might give it a slight bit more life if you polish out the casting for stress risers in the area and then have it shot peened. But I'm doubtful that it will make much difference.
heres a thread you might want to read.
https://fordmuscleforums.comdrag-r...-8-inch-3.html

Then theres these guys with new aluminum 8" Cases
Currie Enterprises
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Last edited by 71hotrodpinto; 05-28-2009 at 10:09 PM.
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Old 05-29-2009, 02:14 PM   #13 (permalink)
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Re: Convert an 8 inch open 3rd mbr to a posi?

In an 8", one case is just as good as the other. Just make sure it has an oil fill port - early housings had the fill port in the housing and not in the case.
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