Drivetrain 91' Mustang - Best Posi Unit For The Street?

Exile

Active Member
Apr 3, 2012
128
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Dallas, Tx
I have a 91' 5.0 Mustang LX-Hatch, and am getting ready to rebuild the 8.8 rear end. It has 4:10 gears with a mini spool in it now, and I absolutely hate driving it on the streets!

What I do know so far is that the new rebuilt rear end will have 3:73 gears, and Moser 31 spline axles.

But im debating on which posi unit that I should go with? Right off im trying to decide between a Detroit Trutrac unit, or a Detroit Locker?

It will mainly be a fun lil daily driver that might see the drag strip maybe a few times a year. I will admit that I do like to get her sideways from time to time, and possibly swinging a few donuts here, and there. (I know, I know)

So that being said I dont think I would want the Detroit locker unit for those reasons? So I am boiling it down to the Detroit Truetrac unit, but I wanted to hear from some other people on what they thought might be the best posi unit for the street?

Any feedback/thoughts/opinions are appreciated!
 
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Get a Trak-Lok from an F-150 (31 spline) and rebuid it with the extra clutch.

Often, you can buy them on ebay all ready to go.

Better street manners than any of the options you've listed. It's just an OEM traction lock, exactly like the one that came in your 91 from the factory but beefed up slightly.
 
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Just buy a new one from ford racing meant for the 03 cobra.
Shop well and you'll find you can get it cheap, i had coupon code for somewhere (can't remember) got mine for $225.
At that price, it's not worth rebuilding anything else.
It's also 31 spline.
 
03/04 cobra diff (stock with carbon fiber clutchs)
05+ have 31 spline like the 03/04's (some had the CF clutch pack)
01 cobra had a 31 spline diff also

and any of the trucks or explorers with 8.8's also had 31's i believe

any of these rebuilt with the CF clutch pack will be good to go!
 
you can buy the clutch pack from summit or ford its around 100 bucks. and you can have the diff from a junk yard for around 50 depending on the yard.

half dozen of 1 or 6 of the other.
im curious of the other threar i just started about the CF clutch pack and the over packed stock pack. which is actually tighter
 
Or how does this new Trac Lok unit with carbon fiber clutches compare to the Cobra/Trucks/Explorers factory Trac Lok units? Better? Worse? Same?

Ford Racing M-4204-F318C
http://www.summitracing.com/parts/FMS-M-4204-F318C/

That's the cobra one.

Just buy it, no sense in building something you can buy, if it were a massive savings i'd say build your own, but by the time you count in going to a JY and finding one or getting one shipped in from ebay, then the clutch kit+shipping, savings are minimal.
 
That's the cobra one.

Just buy it, no sense in building something you can buy, if it were a massive savings i'd say build your own, but by the time you count in going to a JY and finding one or getting one shipped in from ebay, then the clutch kit+shipping, savings are minimal.


Troofs... I tooled around on ebay last night for a little. When I bought mine, it was $110 for one completely rebuilt with the extra clutch. Ready to go. The ones I saw on ebay were over $100 and were NOT rebuilt. So for the $250 or so bux that xp8 is talking about, that's pretty much a steal... Particularly for a new unit with the CF clutch pack installed.
 
bearings
seals
shims
crush sleeve

I have never rebuilt a rear end before, so please bare with me.

Moser 9563 Axle bearings & seals.
http://www.summitracing.com/parts/MSR-9563/

Pinion Nut
http://www.summitracing.com/parts/RAT-1502/

How many Crush Sleeves do I need? 2?
http://www.summitracing.com/search/...e-Model/Ford-8-8-in/Brand/Ratech/?Ns=Rank|Asc

And as far as the shims goes, do I need carrier shims, or pinion shims? Or both?
http://www.summitracing.com/search/Part-Type/Differential-Shims/Axle-Model/Ford-8-8-in/