posi??

MKTSC

Registered User
ok. i've had my 94sc auto for awhile now, and always thought that i had the 3.31 open diff. i have traction control. talking to a fellow sc'er at the meet at bill evanoff's place on sat, got me thinking. he said that his 95 auto had the 3.31 posi. showed me where to pull the axle code inside the door, and i have an identical code to him. he too has traction control. however when i pull into my driveway, or make tight turns sometimes, one wheel will spin even when i'm not on the throttle. this is a common charectaristic to posi rearends. also, when powerbraking or burning out, i've left 2 stripes before. a dead giveaway for posi.

so my question is, do i have posi or not?? where can i find out for sure? thanks. any help will be greatly appreciated.

-matt
 
You actualy have what is called a Limited slip rear end. Theres a clutchpack on each axle inside the rearend housing.
 
is this the same rear end in the erlier model SC's?? LSD is in between posi and open diff is it not??
-matt
 
Here is a sure test. Floor it and crank the wheel. If you get one tire to spin you have an open diff. If you get two solid black marks and your rear end slids around you have a LSD (track-lock) but I seriously doubt that you do with traction assist. Unless someone added it later.

Turn the tracktion assist off also.

Julian

edit posi is eatons model name for their LSD I believe. You ment a LSD is inbetween a locker and an open diff.
 
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well with trac. controll off, i definately get 2 stripes, so i'm assuming that i have the LSD.

is there anywhere where i can read the code off the door sill sticker to make sure?? is there a listing of options and such?
 
I do not know about the SC's with trac assist, did'nt know any of them had it. I cant understand why they would use an open diff in those cars though just because of the traction gadget.


There is a sticker in the drivers side door jamb that should list the codes for the powertrain options installed on the car.

Hmmm........trac assist in a SC? I would'nt want it! LOL!!!
 
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Because the traction assist applies the rear brakes to the side that is spinning. So if you have traction assist and an lsd they will be fighting each other. There is absolutly no point to have both. The traction assist is a horrible design/concept IMO, and ford should have had the lsd in all sc's.

I get 2 solid lines if I go straight from a stop with my open diff (at the moment) so you must try it around a corner. If both tires light up around a corner the you have a lsd.

I have a 95 auto and will be putting a lsd in shortly so I have researched the stuff.

Anyone can correct me if I'm wrong, it happens.

Julian
 
Well I dont doubt that maybe they did that, but you could still do trac assist with a LSD. The LSD hass clutch packs inside the pumpkin 1 on each axle so that the side getting the most traction will slip a little till the other side catch's up, that way when there both spinning you go in a much straighter line. With posi you spin around in circles. Posi strictly race car stuff.
LSD works much like an open diff only tighter.
 
i have axle code 9. it's not listed in tccoa's tech section. alot of other codes are, but code 9 is not.

-matt
 
Well, another thing that you can check is the tag located on one of the diff cover bolts. It will tell you exactly what gears and carrier are in your centersection. If you see "3 31" in the top line of code, that means that you have 3.31 gears with an open carrier. If you see "3L31", that means that you have 3.31 gears with a Trac-Loc unit. This applies for other gear ratios as well.

-Rod
 
Mike 38sc, you had a few inaccurate facts there...

1. you can't do ABS-based traction assist if you have a LSD - Julian's post basically explains why.

2. The LSD does not let the side with more traction "slip a little till the other side catches up". The clutch packs react to torque from the engine, so that as you stomp on it, the clutches clamp to prevent wheel spin. If a wheel starts to spin, less torque is sent to the spinning wheel.

3. "Posi" is just a brand name (Positraction) for the clutch-type LSD made by Eaton. It works just like the Ford Traction-lock, only MUCH better because it has carbon fiber clutches and a heavier spring set. You won't spin around in circles, and it's not strictly race car stuff. But it is a PITA to install one in an SC, ask me how I know...
 
I installed a Ford trac-loc differential in my traction assist equipped 94 SC and have had absolutely no problems what so ever. If I plan on doing any traction challenging driving I just turn traction assist off. :D In fact, I usually turn it off whenever I drive the car since the urge to stomp on it can hit at any time.

My 94 has axle code 9 and it represents 3.31 gears and an open differential.
 
Jimmy 2Coupes,

Can you install just the track-lock piece into the car's original open diff, or do you need a diff with it installed from Ford?
Greatly appreciated,
Julian
 
Just because you leave 2 stripes doesn't mean that you have a LSD. I have had several cars that had open diffs they would spin both tires, not all the time but a lot of the time.

A good test is to raise up the rear so that both rear tires are off of the ground. Leave it in park but E brake has to be off.

Spin one wheel if the other wheel spins in the opposite direction then it is open or fragged.

If you cannot turn the wheel then it has an LSD.

Jeff
 
T-bird4vr said:
Here is a sure test. Floor it and crank the wheel. If you get one tire to spin you have an open diff. If you get two solid black marks and your rear end slids around you have a LSD (track-lock) but I seriously doubt that you do with traction assist. Unless someone added it later.

Turn the tracktion assist off also.

Julian

edit posi is eatons model name for their LSD I believe. You ment a LSD is inbetween a locker and an open diff.

Thats what I said. Mine spins both tires going straight, but as soon as you get more weight on one tire you get one leggers.
Julian
 
T-bird4vr said:
Jimmy 2Coupes,

Can you install just the track-lock piece into the car's original open diff, or do you need a diff with it installed from Ford?
Greatly appreciated,
Julian

Yes, but you will have to have the gears setup by a shop. It will usually cost about $200 with you bringing the parts. Good time to replace bearings and seals.

Jeff
 
Rob Noth said:
Mike 38sc, you had a few inaccurate facts there...

1. you can't do ABS-based traction assist if you have a LSD - Julian's post basically explains why.

2. The LSD does not let the side with more traction "slip a little till the other side catches up". The clutch packs react to torque from the engine, so that as you stomp on it, the clutches clamp to prevent wheel spin. If a wheel starts to spin, less torque is sent to the spinning wheel.

3. "Posi" is just a brand name (Positraction) for the clutch-type LSD made by Eaton. It works just like the Ford Traction-lock, only MUCH better because it has carbon fiber clutches and a heavier spring set. You won't spin around in circles, and it's not strictly race car stuff. But it is a PITA to install one in an SC, ask me how I know...
Well Rob a few things are wrong here:

1. Yes you can, in fact Ford sells a car in Europe called the Mondeo there is one model of it with 4 whell drive front and rear LSD's and trac control. My buddy in Germany owns one and its a very nice ride I might add.

2. I still stand by my part of this statement. The way you describe the operation of the LSD is not how it works. Clutch's are in there and you said so yourself. Clutch's are for give or slip. Thats the only reason for them.

3. You got me on that. I am guilty of using a patheticaly overused generic name that once a long time ago was a name given to what is actually a live axle. Meaning no diff at all and no clutch's just both axles tied together as 1. Just a spool conecting both axles solid making it 1. That is strictly race car stuff and that is what I was talking about when I used the term posi.
Sorry about the confusion. My bad.:)
 
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