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Discussion Starter #1
The tag on my rear diff says that I have a 3.08 open diff but if you get on it from a stop it leaves two tire marks. I guess its possible someone put in a limited slip before I got it but doubtful. I have rear disc brakes, dont know if that makes a difference as far as option packages?
 

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̇
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Have you checked your drivers side door jamb sticker?

Under the "AX" on the door jam sticker:

Gears and Axles

Most likely you have an open rear end..Even with an open rear end if you (power brake) it on a flat dry surface you can get both tires to lay tracks..

One way to check to see if you have an open rear end is to lift up the rear of the car..Then spin one of the rear wheels by hand..

The other rear wheel will spin in the opposite direction if you have an open rear end..

Of course if you do have a Trac-Lok, and it is really worn out this test may not work..I've seen that happen before too.. :rolleyes:

In that case..Just to be 100% sure of what you got in the rear end the differential cover has to come off..





Rayo..
 

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1997 Thunderbird 4.6, 1998 Mark VIII LSC
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You can leave parallel skid marks with an open diff. Did it a couple times in my old 3.8 Cougar... no brakes involved. :rolleyes:
 

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Discussion Starter #6
Every other car I had that had an open diff only did the one wheel peel. So seeing an open diff leaving two marks had me wondering.
 

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Pretty sure from what you all describe is an open, that what's in mine. But with 2.73's wheel spin from a dead stop is not an issue. However, mainly due to the surface I'm on, I get 1 or both breaking loose, just never really know which is going to happen.
 

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The Parts Guy
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If you get really curious, pop the diff cover and have a look. The "S" spring is an immediate giveaway.
 

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How strong is a properly functioning 8.8 trac loc? I'm putting one in soon and curious how different driving the car will be. I have never have driven a Ford with one before. I have driven a few trucks with lockers and they come on quick and hit hard.
 

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Since the Cougar has always had a TracLok in it, I can't say for sure - but really, with my driving, I can't tell much difference on dry ground as with the open diff in the Dakota pickup.

Slick streets, OTOH ... *grins* Rather have the Cougar diff.

(Which is why I'm saving up for a Dana LSD for the Dakota.)

RwP
 

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They drive completely differently.

A one-leg rear will hold a line thru a corner better at wot; a locker will drift. :)
 

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The Parts Guy
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There seems to be some confusion between a limited-slip (like a Traction-Lok) and a locker (Detroit Locker, ARB, etc.) . They behave quite differently.
 

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Disclaimer: I've never driven a "Real" geared type locker rear end.

Lazarus is easy to "fine steer" with the throttle in curves, as most of my older 'locker' Fords were. :)

The one side drive doesn't lose the line in a curve as easy with increasing throttle; that's the biggest difference I notice. :)

It's much easier to do donuts with the trac-lok, lol.

I just don't do a lot of wot action from a stop... :D
 

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LSD > than all in the real world. Lockers have their place but not on a IRS IMO, or on the street.

IMO Geared LSDs are the best.
 

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It seems like the Trak-loc makes a tire skip occasionally, and imho, that makes it "driftier".

Whoever has the least load 'barks' a bit in a sharp corner, kinda, to give up the bind.

(We have curvies here so sharp you can see both bumpers at the same time; ymmv. :) )
 

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They drive completely differently.

A one-leg rear will hold a line thru a corner better at wot; a locker will drift. :)
I agree,
The open on my 95, I could take an aggressive turn and stomp on the gas I might get a little loss of traction. Then, if I PB I could eventually get both tires roasting leaving 2 marks one darker then the other. My 96, had a aftermarket trac-loc installed before I bought it. Now if I do the same driving with this I get drifting out of corners and both tires start to spin at once not just one then the other.
 

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I saw this post in an older thread:

... I'm still using the stock size S spring and standard friction/steel stack in my 91 SC. They were replaced at around 85K miles when installing gears, but no upgrades over stock. My 93 SC has an Auburn Pro and the only difference you can feel when driving is when the tires spin. On the 91 SC with stock trac loc it kicks sideways, when the 93 SC spins with the Auburn Pro it tracks dead straight.
...
David
I'll assume this is what I'm missing with only Trac-lok experience to go by. :)

This exactly describes my experience with the T-L diff.

I'm going to have to look into this further. :D
 

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IMO Geared LSDs are the best.
A Torsen gear driven LSD sucks, at least on a high powered turbo car. On a big turbo (laggy) setup, when the boost hits, the back end kicks out hard at 55-60 MPH! That can be very dangerous. After switching to a clutch type LSD, the Toyota tracks straight.

And for the record, every open diff car I have ever has only spun one wheel on a dry surface. The only exception was when turning on slick surfaces, both would spin enough to kick the back end out or do donuts.

Al
 

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I ran a Torsen T2 on my Bird for 10 years and was very happy with it. It was especially helpful when I was still daily driving in Michigan winters. Also did pretty well at the drag strip with 375 rear wheel hp, although I did have to preload the right rear tire to get it to launch straight. When I did the rear end upgrade two years ago, I switched to a Detroit TruTrac for improved strength.
 

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Question : On my trip to the boneyard today, I checked the the door sticker and rear axles on the Birds & Cougars there. Only 1, a '94, has rear discs and a Z code axle. Is that rear axle assembly a direct fit in place of a '91 rear axle assembly??
 
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