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spools, lockers and posi's

7334 Views 20 Replies 11 Participants Last post by  wstout
i saw this in another thread:

Full Spool > Locker > Posi

someone explain exactly what each does. i have my own ideas, but i want a complete explaination from someone who really knows.
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A spool has no moving parts....the ring gear bolts to it and the axles go in the sides and it locks both axles full time. Ideal for drag racing, bad for taking turns as the inside wheel will scrub.

Locker....locks both axles under acceleration, in cornering it unlocks the inside wheel which will just freewheel, while the outside wheel gets the power.

Differential applies power equally to each wheel unless one slips, then it transfers power to the one with grip. Both wheels drive through corners at different rates.

Open differential drives both until one loses grip, then the one w/o grip gets all the power.
i seen some posts about people with lockers complaining and wanting a spool (on street cars). why is that? it seems that a locker or a diff would be the best.

Differential applies power equally to each wheel unless one slips, then it transfers power to the one with grip. Both wheels drive through corners at different rates.
a posi, correct? and if this is what is commonly referred to as a posi, then what is an open diff usually reffered to as? or are both just called posi's? but regardless, both are not usually used for hard track use...?

Open differential drives both until one loses grip, then the one w/o grip gets all the power.
so if im taking a hard right hand turn, and the right wheel starts to lose grip, all the power would be transferred to the right wheel, and leave the left 'freewheeling'?
IMHO versus the old lockers Id just as soon have a spool...I drove my full spool car on the street today...It barks a little if you corner quickly...But hardly a pain>>>Would not recommend for daily driving..


Lockers have their fair share of problems too...a locker will not handle the abuse a spool will and its heavier, and its still noisy as all get out(although the newer style are supposed to be quieter) and they are quite a bit more expensive...


Funny what people consider streetable...I justt drove my GTA about 60 miles today...the only PITFA part of it was exhaust noise... But My car was FULL of non streetable stuff according to most.. Solid roller cam, Full Spool, wolfe rcecraft Solid sway bar, 90/10 shocks, Manual steering, manual brakes, hell I even kept the parachute on it...LOL... I was fine...was cruising between 60-80 most of the time... down country roads... No problems... I was no where close to being UNSAFE...I mean you just use common sense... I did not hit a hairpin at 100+ and expect the car to hold like a gtp car..
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see, thats the thing. i dont think i want a spool, since its a DD. some people say its fine, but i dont think ill be able to take it. a locker is noisy and i dont think it would be right for me either. a posi is the best choice, but weak :(
Basically the spool would be hard on tires for a DD...Plus I noticed that the car seems to Understeer with the spool...Its more noticable at low speeds...its seems fine 25mph and above>>>But like in a parking lot..it seems to push..
There are now "soft lockers" that aren't as noisy.

And an open diff is just an open diff, and should never be called a posi. Posi is sort for positraction.

Yes, on an open rear if one spins you are just free wheeling. My '85 camaro was like that.
i get spools and lockers now, but the differential thing is confusing now. ive never heard anyone talking about just a differential. only posi's and lockers and spools, and maybe ive heard open diff before....but not just differential.

like, ive heard 'i just bought a new spool', or 'i just picked up a new auburn posi', but never 'i just picked up a new differential..'

get what im saying?
they are ALL types of differentials.
Chris 96 WS6 said:
they are ALL types of differentials.
exactly... you say i got a new rear... but a 12bolt a 9" and a 10 bolt are all rears...
same thing here.
differential is what they ARE, posi , open, ect.ect.ect. is the specific TYPE.

As for a spool and if it is streetable, the tire you run also has alot to do with it.
if you are on 15" et streets then you will most likly never notice anything differant as the soft sidewall flexes and absorbs it...

if your on 18's with rubberband tires (almost no sidewal hight at all) then it will drive you nuts
I just got done building my 9" and got it under the car a couple weeks ago. I put a Tractech locker in mine and I can't wait to get that big piece o shit out of it!! I hate that thing so bad I'm going with a spool. I don't know if all lockers are like this thing but if they are then they should be outlawed. It has a tremendous amount of slack in it and I'm afraid of racing it like that. Just running thru the gears hard makes me cringe evertime I hit the clutch hard.

Plus when I'm making a turn from a stand still it will lock, unlock, lock, unlock. The motor revs each time it unlocks then when it locks back up it makes the car lunge forward. It's doing this all at the same time and it gets the car to bouncing, bouncing so bad that it will pull my foot off the gas then slam it back down on the gas making the whole mess that much worse! It did it to me last night on the way home from work and it was so bad I just started LMAO. :roflmao:

I don't have stock rear suspension anymore, I have Z bars that I built and this might amplify the whole lunging/bouncing thing because the car is much more sensitive in the rear now do to it being lifted on takeoff instead of squatting but I do not recommend a Tractech locker for a Ford 9" mainly because of the slack mine has. The manual that came with the locker says it's normal to have up to a 1/4 turn of play at the driveshaft with this thing, I think that's ridiculous! Maybe I just got a bad one but this is my first AND last locker I will ever own.

I'll have it for sale come next week if anybody is interested. :lol:
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Jaberwaki said:
As for a spool and if it is streetable, the tire you run also has alot to do with it.
if you are on 15" et streets then you will most likly never notice anything differant as the soft sidewall flexes and absorbs it...

now wouldnt that just ruin your tire? et streets arent one for many miles if driven all the time but wouldnt the turns ruin them faster??
snakeoilperformance said:
now wouldnt that just ruin your tire? et streets arent one for many miles if driven all the time but wouldnt the turns ruin them faster??
alittle faster for sure, but not as bad as you might think... several people local here run that kind of set up :cool:
yea my boss has a turbo 96t/a and he used to run it with a spool and et streets i belive. went 9s driven to and from the track with 300lbs of stereo eqipment.

oh and its for sale...
9's at full weight is crasy!!
what would be a diff for road racing? i know auburn makes a diff for road racin but i dunno what class its in.
I'd suggest either a posi or a locker for road racing or AutoX.
Daily driving problems from a locker all come from getting used to it. Mine's even broken (it's hard to break a locker, trust me, lol), and I can drive it so that no one else would even notice it's there (other than the click click click click). The slack is ok to be there, just when you stage take the slack out and it'll minimize some shock on the rear.
The rear end/gear/axle is called a differential because it causes the motion of the drive shaft to go in a different direction than what it started out in, i.e., it transfers the power into a 90 right angle from the original direction. A peg leg or non-posi dif will only ever spin 1 tire (if memory serves me right the left rear). A posi (positraction is a GM coined term) will turn both tires when it senses slippage from the driven tire (it uses clutches in the housing to accomplish this). A locker (a term coined from the manufacturer, Detroit Locker) stays locked until it senses a difference in tire speed, i.e., while turning corners, and then it locks, unlocks, locks, unlocks, allowing the tire on the outside to turn faster. Both posi's and locker's remain driving both tires when the car is going straight. A spool is permanently coupled to both tires. The outside tire will chirp around a corner as it's trying to go as slow as the inside tire. Hope this helped.
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