Difficulty Poll on Putting Positraction in/on Car

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  #1  
Old 12-04-04, 08:31 AM
Aegis
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Difficulty Poll on Putting Positraction in/on Car

So...my car generally doesn't go anywhere in the snow, forward nor back. This is a bit overstated, but suffice to say I get honked at occasionally when trying to go through an intersection with a green light in the snow. I'm not much a car person and was wondering just how difficult a job it would be to put positraction (or some type of LSD) on my Grand Marquis. I've replaced air springs with coils, played with shocks as well as replaced the brake systems on various cars that I've owned, but never really played with the actual drive mechanisms. My question then: How difficult & involved is type of job? I realize it may be a bit difficult to simply say, 'It's this difficult.' especially without my establishing any type of baseline, but I'm just looking for people's thoughts & opinions.

Thanks!
 
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  #2  
Old 12-04-04, 03:08 PM
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It really isn't that difficult to do. All you have to do is change the entire differential cluster. Just transfer the ring gear to the posi cluster. That said, I don't think you'd get the result your looking for. The problem with a posi on a slippery road is that when it spins, you lose all control of the back of the car. You won't be able to keep it going straight under acceleration.
 
  #3  
Old 12-04-04, 04:33 PM
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Aegis,

I am assuming that this Marquis is a RWD.

I would suggest that the problem may start with your tires.
If allowed where you are two studded tires on the rear with a standard diff would be better than poor tires with posi.
If studded are not allowed, tires that are specifically for ice are best.
Also, it is common here to load up the trunk of a full size RWD car with a couple of hundred pounds of weight.
 
  #4  
Old 12-05-04, 04:43 PM
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I had a 92 Crown Vic with the same problem. A pair of winter rims and a great pair of snow tires made all the difference in the world.

My $0.02
 
  #5  
Old 12-06-04, 06:54 AM
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Ack, this is a tough decision, I've got these two little characters, the angel & devil, as they're often portrayed:

Responsibilty says, "get better snow tires & deal with it; it'll be cheaper than replacing the differential, not to mention easier and you won't be spending money on something you're going to get rid of soon anyway."

Fun says, "Remember your old '87 Caprice cop car? The fish-tailin' donut makin' machine? You could make this one like that. Increase forward & backward AND side to side mobility!"

Basically, I can see where it doesn't make much sense to do anything but get a good set of winter tires, but I desperately want positraction back again. If only to abuse it, hehe.
 
  #6  
Old 12-06-04, 08:43 AM
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Aha-now the truth comes out
Haha!

Does you Merc have the 4.6 or 5.0 and 7.5 or 8.8 rear?
 
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Old 12-06-04, 09:05 AM
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8.8 I believe, but I've yet to confirm it. There was a tag secured by a bolt in the coverplate on the diff with the following numbers; I've yet to decipher it:

The "_" are there to preserve relative spacings.

_C002A
08_88_2A02

The "C" may have been another 0, but were I to put money on it, I'd say it was a C.

And in my defense, there is truth to the claim that positraction & other forms of limited slip differentials are better in snow than an open diff.
 
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Old 12-06-04, 09:20 AM
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Thumbs up Speaking about snow, today happens to be "snow day" here.

Had to slip and slide home to get the 4x4 so I can go and fix the wife's 95 Caravan.
Seems the fan belt doesn't like to stay on when she ploughed her way to work!

Curious to know roughly where you are.
There are a lot of folks that don't ever really get to know what living in snow country is all about.
 
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Old 12-06-04, 09:29 AM
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Smile

Originally Posted by Aegis
8.8 I believe, but I've yet to confirm it. There was a tag secured by a bolt in the coverplate on the diff with the following numbers; I've yet to decipher it:

The "_" are there to preserve relative spacings.

_C002A
08_88_2A02

The "C" may have been another 0, but were I to put money on it, I'd say it was a C.

And in my defense, there is truth to the claim that positraction & other forms of limited slip differentials are better in snow than an open diff.
I may be able to decipher that later
It may be easy to get a Traction-Lock deal in there, I'll have time later to check it out
And yes that's why LSDs were first put on cars right?
The fun stuff was just a side effect!
 
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Old 12-06-04, 10:19 AM
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Rural Michigan for most of my driving career, though now I'm basically in Detroit.
 
  #11  
Old 12-06-04, 12:41 PM
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interesing

This is an interesting topic because I also need a limited slip in my Tacoma. Options are a locker operated with air or a limited slip. I have heard a limited slip is more drivable on the street when going around corners.and a true locker can be a bear to drive and tear up tires and drive train components on the street. Also on a true locker you need all the stuff to lock it like air source.air lines etc.
The LSD seems a lot more easy and street friendly.
 
  #12  
Old 12-06-04, 02:07 PM
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I was in a rush at the time
I wrote Traction-Loc when I ment the Ford brand name for Posi-Traction
I still can't remember what it's called
It'll come to me
 
  #13  
Old 12-06-04, 02:11 PM
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I was kinda right
It's Traction Lok
And you are absolutly correct about the true lockers
You would have to be a hard core off-roader or drag racer for those
 
  #14  
Old 12-06-04, 02:13 PM
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Originally Posted by Aegis
And in my defense, there is truth to the claim that positraction & other forms of limited slip differentials are better in snow than an open diff.
They may have more traction but the second you break them loose, you'll do a u-turn before you know what happened.
 
  #15  
Old 12-06-04, 02:53 PM
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If that's an '83 it'll be easy to find a Traction Lok that fits
That and the next few years it was a common 28 tooth unit
If it's a '93 it'll be trickier
I'm sure it's an 8.8
Just need to know what year
 
  #16  
Old 12-06-04, 07:02 PM
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Slickshift, I imagine they only put 7.5s with 28 spline axles in the Vics and Marquis. Did they upgrade them eventually to 8.8s with 31 spline? Seems hard to believe, except maybe on police interceptors.
If they did, i'm jealous my '84 only came with a tiny 7.5 with 28 splines. I'm just a set of slicks away from watching that explode.
 
  #17  
Old 12-06-04, 07:12 PM
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I'd think the same thing but the code says it's an 8.8
"08_88_2A02"
The double 8 is in the right spot
 
  #18  
Old 12-06-04, 07:15 PM
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Originally Posted by aaronr121
I'm just a set of slicks away from watching that explode.
lol!
It might survive the slicks...
For a while
 
  #19  
Old 12-07-04, 12:47 AM
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Desi, as I mentioned, my first car was an '87 Caprice 9C1...signifying cop car...LT1 'vette engine, a light rear end (relative to the rest of the car), and positraction...I learned to drive in Michigan winters (not the worst by far, but not nice either) with this thing; I'm intimately familiar with the way posi likes to cause nose reversals.

Anyway, it's a '92 Grand Marquis, if that helps anything.
 

Last edited by Aegis; 12-07-04 at 12:59 AM.
  #20  
Old 12-07-04, 05:41 AM
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whats the deal?

OK I am getting mixed signals about Positrac what is it good for?It seems that on slippery roads you do 180s. As far as straight line take offs we all know that if you spin the tires you lose traction and launch slower .Maybe besides even tire wear in the back what are the benifits?
 
  #21  
Old 12-07-04, 06:02 AM
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Originally Posted by aaronr121
Slickshift, I imagine they only put 7.5s with 28 spline axles in the Vics and Marquis. Did they upgrade them eventually to 8.8s with 31 spline? Seems hard to believe, except maybe on police interceptors.
Apparently it was an option available on some non-ABS Marquis's...Marquises...Marquii?
However, it seems to be a 28 spline, like the Mustangs

Which means Aegis, the parts are plentiful and the swap, though maybe not a shadetree project (diffs do need some sensitive adjustments), won't require any mods or expensive one-off parts

As to how easy, I have a specialty shop do mine so I really can't comment
But I do know the procedure is as Desi501 described it
You basically take out a cluster (of gears), and install the new one
It must line up and you may need shims and if it's wrong you chew it up quick, but many are comfortable with doing this in their garage

You might want to call a few shops and see what they get for it
And/or read a few books on DIYing it
 
  #22  
Old 12-07-04, 06:28 AM
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Originally Posted by michael van
OK I am getting mixed signals about Positrac what is it good for?It seems that on slippery roads you do 180s. As far as straight line take offs we all know that if you spin the tires you lose traction and launch slower .Maybe besides even tire wear in the back what are the benifits?
Posi won't make you do a 180, but it does take more skill that a front wheeler in the wet
The idea is that if one wheel is slipping (let's say it's on a frozen puddle), you still have power to the other wheel (that's not) and you can control the car better

Two tires w/power = more traction that one
If you are spinning (dry/straight-line) your power is over whelming your tires
 
  #23  
Old 12-07-04, 06:34 AM
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To address that question to the original post, if only one wheel is powered, and it's slipping because it's in snow, that's it
On a posi, power is transfered to the other wheel to get traction, maybe you'll get out of that snowbank quicker!
 
  #24  
Old 12-07-04, 09:13 AM
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As slick mentioned, it isn't like driving a spinning top. You'll get alot more traction than with an open diff. If both wheels are on snow/ice, with posi, if you overdo it, you'll end up having both tires spinning & possibly lose control, whereas with an open, you'll only have the one with the least traction spinning, which isn't very serious...you just go slower, or not at all.

On the otherhand, your friends will be begging to drive your car on dirt roads or snowy parking lots...
 
  #25  
Old 12-07-04, 03:36 PM
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You'll probably do a lot better traction wise if you just take that new 100lb differential assembly and just put it in the trunk..............lol The extra weight will be more help than the extra traction.
 
  #26  
Old 12-07-04, 04:23 PM
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in moderation

I guess with a Posi on ice it is very critical on throttle input on ice or water. I can see how it would benefit on a dry road under heavy acceleration with two patches of rubber pushing the vehicle forward.(less chance of tires breaking free.
There are too many things to think about posi or open diff using the brake to transfer power. Or maybe a part time locker like the ARB. maybe a posi with 400 pounds of sand in the bed?
 
  #27  
Old 12-07-04, 05:01 PM
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I beleive the original question about difficulty has been answered so don't start an arguement about the differential subject or I will close the post.By the way in 2-3 hours you could swap out the entire axle assembly with ordinary hand tools(and your skill level) and not worry about any adjustments.So it's about as easy as you can get after you spend the money.
 
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