Spools Vs Locker or Posi

[muscletruck]

Ok...SO i was looking through the Jegs and Summit Catalog and i notice that Spools and Posi Units have a severly different price...Spools were much cheaper and they seem to be stronger...Are spools dangerous on the street?... I DONT GET IT!! IF there is no difference... Spools seem the way to go...no clutches to replace or maintain...theres gotta be a catch..thanks all

[ebfabman]

Spools are not for street use. They keep the wheels locked together. This means when you turn, both wheels will be turning as if they are in a straight line, no compensation for the smaller arc of the inside wheel. The result is a squeeling of the tires every time you turn. Thats unnecessary wear on the axels as well.

A locker locks both wheels when power is applied. Still not really a street piece.

You need a posi designed for street use,IMO.

[muscletruck]

I LOVE THIS BOARD.....I POST IT........5 Minutes LATER.....BAM! got the answer...thanx fabman

[Michael A. K. G]

An "automatic" locker can be used on the street, but they are kind of noisy, and they don't always do what you want (consider a hard curve where the outside drive wheel starts to squeal). An air locker can be disengaged on the street and engaged when desired (do NOT engage one on dry pavement). A spool is just like a permanently locked locker, and is strictly for off-road.

But a Posi is just about perfect for pavement, and occasional slippery situations (like snow/ice, or gravel).

With a locker or spool, there is no designed "breakaway." If the tires are really stuck and you push it hard enough, the axle will break. With a Posi, the clutch disks just give, as in a normal turn.

I have a Posi on my offroad truck, a Bronco II. It works far better than one would expect, even in deep sand. As for most Bronco IIs, the front diff is open. And it also works nicely on pavement (not in 4x4, though -- Bronco IIs have very simple 4x4 systems that do not take well to pavement).

All traction-responsive differentials have behaviors under slipping that have to be understood and compensated for. Especially, if one rear tire is slipping and the other is not, the vehicle will attempt to center the tire with traction. This means the rear end is going to swing wide.

[Canada20]

So would a posi be safer for winter driving? I've heard of problems with directional stability with lockers but I wonder if posi's would give the stability of an open diff but some of the traction of a locker when you need it like at a stoplight or starting up a hill.

Greg

[COBALT]

My detroit locker is great. I have a lot of good traction, and drive my truck daily. There's sometimes a little noise, but rarely. The good thing with the LWB is its farther back there. I get plenty of street traction, and I haven't had too many difficulties.

The only thing I don't like is the introduction of play in the driveline. You can feel it when you accelerate/decelerate. Nothing I can do about it. Therefore, I'll probably step to a posi unit when I build up the rear chasis, because I don't like give in the driveline.

When it snowed last winter I didn't have too many problems. You just have to be careful. Problem with posi is fishtailing vs. just spinning out with spiders. With lockers you just get more wheel spin on both sides, and going around corners you could loose control when the inner wheel engages.

By no means would I even think about spools unless you drive a train. You'll just be eating your axles up.

[67 SS]

My 76 4WD has a Posi in the back.The only time I've had to get out and dig to get it unstuck was when I went down a skidder trail in the snow and hit a hole bigger than my tires.The axles dug in the ground til my tires stopped touching the ground.As far as winter driving,any vehicle on an angle will try to slide one way or another no matter what you're running,but a posi will help you get traction.I bought this truck years ago,the first one I drove with a working posi,and it made a believer out of me.

[Michael A. K. G]

Originally posted by C(anda)20
So would a posi be safer for winter driving? I've heard of problems with directional stability with lockers but I wonder if posi's would give the stability of an open diff but some of the traction of a locker when you need it like at a stoplight or starting up a hill.

They are a compromise between a locker and an open diff. They will lock the wheels together, to a point. And they are "always on," unlike a locker. This means the stability will be enhanced over a locker, but regressed with respect to an open diff.

Posi diffs, at least in the rear, are a very sensible choice for a mostly-pavement vehicle. On a 4x4, you can put them in the front also, but the traction squirrliness you get from that will also affect the steering. This is not a good thing, IMO. But some Jeeps do it anyway, and work fine.

[O'l Buck]

the 67 K-20 I posted pics of has locked diffs on both ends...it hops around corners and is a real bear to turn in the mud, but it will go anywhere.....nothing slips anywhere, kinda hard on tires and will wear you out to drive it due to the harder turning of no slip, and no p/s.......but hey.....it'll go anywhere!!

[stevesburb]

I have a spool in the rear of my 72 bronco. On the street it doesn't handle any worse than a detroit, but at least it is consistant. The chirp isn't that bad. You just don't gas it around corners. That is with 33" AT's. Not sure about snow driving with it.

[70c10]

Are these any good and how hard to install on a 70' with a 12 bolt with 3:73's?. Thanks

[Tracy Focht]

I had the Powertrax locker...trsh IMHO...so I threw out a $419 item, got a $99 mini-spool well over a year ago, and works for me. Sure, go thru a set of tire about each year, but with my leadfoot, bet I would anyways.

[Church]

If you want the best of both worlds get the ARB air locker. It is more expensive but you have an open diff until you hit a button which activates the onboard air compressor to switch it over to positive traction. At this point it acts like the spools, there is no slippage what so ever. They make them for the front and rear. I have them on my Jeep are they have got me out of a bind or three!

[Canada20]

A couple of things we haven't mentioned about these things are toughness and cost to repair. I know that a good locker is about as bomb-proof as you can get without going as far as a spool but what about the durability of a posi? They're designed to wear out eventually just like a clutch but how long do they last, what power levels can they cope with and how expensive are they to rebuild?

Come to think of it...when they wear out, what happens? Seems to me they just behave like an open diff.

Thanks,


Greg

BTW the air locker idea sounds like a pretty good alternative; can you engage/disengage on the fly?

[Michael A. K. G]

Yes, a worn out Posi behaves just like an open diff.

"No slip whatsoever" is not necessarily a good thing. If you are really "stuck" with traction (as happens to rock crawlers sometimes) something has to give. On a Posi, the clutches slip. On a locker, some part of the driveaxle breaks.

ARB air lockers do allow you to turn on and off the locker as you need. But they don't help you for that slippery spot on the road, unless you train yourself to hit the locker (probably not a good idea due to breakage risk if the other side does have full traction). Posi diffs are on all the time.

They aren't THAT bad to rebuild. Really cheap compared to a chipped ring gear.

[big71]

this rearend code says it a locker can ya tell if it is or just a posi

[Michael A. K. G]

Originally posted by big71
this rearend code says it a locker can ya tell if it is or just a posi

It sure looks like a Posi. You can see the S-spring preloader and the clutch disks on one side.

That *might* be part of a locking mechanism, but I doubt it.