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"70" Cougar 03-01-2006 06:52 PM

difference/pros/cons of spool and mini spool?
Well traction is the name of the game and im getting ready to start thinking about my rear end. Now for what ever reason i have come to the conclusion that i want a full time locked rear end.. two tire fire .. always. Now don't now much other then basically they do the same job.. but.. exactly is the difference between a spool and a mini spool .. are they the same thing.. just one is smaller.. and if so .. why and what are pros and cons for both ?


bill C.

sha_ba_do_bang 03-01-2006 07:37 PM

you can't really drive on the street with a locked rear, if its drag only that cool but it will be a pain in the *** to move around, you'll go thru more axles and rear end parts your might as well buy a locker

Centerline 03-01-2006 08:35 PM

Do a search on this site and you'll find this subject has been discussed many times.

Bottom line is that a spool on the street will not only eventually break parts (axles) but they are dangerous on wet roads. A spool is designed for drag racing only. They aren't designed for turns and put a tremendous strain on your axles not to mention chewing up your tires.

"70" Cougar 03-01-2006 11:31 PM

Well actually im planning on having one " third member" for street and one " third member" for strip so.. that being said... can anyone explain to me how to install a mini spool in a 9 inch carrier. I know how to remove the pod from the diff.. so from having it on the bench .. and ready to go.. wats next folks?



its a car and not that heavy with 245 15's so there not amazing slicks so i cant see them ripping axles apart. But yes i guess anything is possible.

M&M CUSTOM 03-02-2006 01:34 AM

A mini spool fits inside the standard open differential carrier replacing the spider gear assembly completely, same thing as a mini-locker like Powertrax/Lock-Rite/ or Detroit EZ-locker.

A full spool replaces the ring gear carrier and spider gear assemblies completely with a single piece.

They both do the same thing.

As you said you are going to swap out the center sections for street and strip, I will leave this thread open for discussion, the spool on the street is a no-no around here and we immediately let it be known and usually immediately close those threads too.

"70" Cougar 03-02-2006 06:55 AM

Well i think ill go with the Detroit's ez. sounds like itl be less expensive then the full setup. thanks for the timely response.. and i appreciate leaving the thread open for possible discussion. i live about 45 minutes away from Mission Raceway /drag-strip and i really don't see the point in street racing and haveing the chance of hurting my car or even worse killin persons.

thanks again


lowROLLERchevy 03-02-2006 07:10 AM

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^^^^ good attitude

plus, hitting the wall at the track causes ALOT less damage then hitting a house or a grove of trees, not to mention all the other things that can go wrong w/ wrecking on the street

farna 03-02-2006 07:19 AM

You don't need big tires to put a big strain on the axles and gears. When you turn, the inside wheel wants to run around something like a 14' radius, and the outside wheel around a 19' radius (depends on size of vehicle, but 60" track is average). This makes the two axles "fight" each other -- the outer wants to go faster, the inner slower. So the axles try to twist and the tires grind each other down. Whichever is weakest loses, but all parts get a lot of strain. Nothing will break right away, but the added strain will cause a lot quicker failure -- something WILL eventually break, and when it does, it will be catastrophic.

Ever seen or heard a car snap an axle? I've been close by when it happened at a dirt track -- welded differential broke in the pit area when the guy was turning the car around. We thought someone had fired a shot gun! Needless to say, no racing for that guy that night. A spool (or even mini spool) would hold up a bit better than welded spider gears due to the heat caused by the welding. That just means the spool/mini would cause a bigger bang when it broke.

The solution is a locker for street/strip use. If you don't like the ratcheting noise of a limited slip, get something like an air locker made mainly for 4x4 vehicles. Those lock on demand, and are really safer than a limited slip. Even limited slip is dangerous on slippery surfaces (wet, icy, loose sand, etc.). Once the wheels lock it's just like a spool -- the car will slide sideways with both wheels spinning and the driver has less control over the vehicle. The air locker only locks when you ask for it.

A local rodder with a blown 350 in a 'glass 32 decided to see if he could break the wheels loose at 50 mph in high gear, so he floored it. Sure will break them loose! Slid sideways and went off the road, causeing a little frame damage. Luckily just the running board and fender on one side were destroyed, and a slightly bent frame -- no people damage (except for some clothes...). With a "one legger" only one wheel would break loose and the other would maintain enough traction to keep the car from sliding sideways.

malc 03-02-2006 08:27 AM

Ive had one of these Powertrax
syatems in my Camaro for many years now and it works great.
Clicks a little going round tight corners but does the job in a straight line.
It was the best solution for me as the ring and pinion stay in place during installation.Got it from Summit.

"70" Cougar 03-02-2006 05:24 PM

i appreciate the info and suggestions of lockers and limited slip diffs. im on my way to making some good pass's at the strip . Now could use instructions on how to install a locker .. the type that fits inside the ring gear. thanks again guys keep the good calls commin !(y)


sicksixseven 03-02-2006 06:07 PM

Being a member of the offroad community too allows me to look at this question a little different. If you plan on doing a mini spool, forget that, weld it up. If you want a full spool, forget that, weld it up. People can say that they will break, that they will cause damage, but I can attest to the fact that they don't. I have run a welded rear and a welded front and never had a problem. If you want a lunchbox style locker, look into an Aussie. See them here: . I am not sure what axle you are running, but they have them for most any application. I wouldnt waste my time or money on a full Detroit, way too much, and they break if you break an inner. The Aussie is by far the best lunchbox style, meaning that it replaces the spider gears in the carrier with the locking mechanism. See install here: . I have two of them for my Toyota once I get the time/effort/motivation. That's about all I can think of. Good luck with your choice.


"70" Cougar 03-02-2006 06:20 PM

hey thanks sicksixseven if it helps its a 9 inch for a '70 Mercury Cougar with 28 spline axles .


Centerline 03-02-2006 06:53 PM


Originally Posted by sicksixseven
.......People can say that they will break, that they will cause damage, but I can attest to the fact that they don't. .......

I'm amazed that at the ripe old age of 19 and with your vast experience (most likely measured in months) in the automotive world that you speak with such authority. Must be a prodigy of some kind.

lowROLLERchevy 03-02-2006 11:05 PM

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welding them migth be fine in the ofroad setting, but your also not dealing with the as much stress as you are when you launch a 3500 lb car out of lights at the track

hardened materials like spider gears should NEVER EVER be welded for racing situations

ever seen a spider gear shatter under extreme stress, exit thru the back of a ford 9 inch housing, and implant itself into the pavement ?

thats enough force for the fragment to have shattered a leg bone if it had come out parallel with the gound. race track officials dont go to work willing to be shot by your car just because you decided to save $200

NOW i think its time to lock this thread. sorry cougar, but i think you know who you can PM if you need more information. either that or strat a new thread with specific questions so that the welding idea id specificly excluded from being a posible response

something like "ive narrowed it down to XXX brand mini spool and XXX spool, and was curious blah blah balh"

"70" Cougar 03-02-2006 11:17 PM

Welli guess ive come up on one of the big dogs eh.. well sure if i have any more questions on the subject ill be sure to stear clear of the " w.....g" subject even thow i havent realy said i was gonna do it or intended of doing it, or even thinking of it. next topic i guess


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