posi, limited slip, open

[kevncar]

I am going to convert the rearend of my 67 over to 5-lug axles and thought while I was in there I might upgrade the rearend to a posi. My question is what is the difference and what should I be shopping for?

My truck is a toy, meaning I don't commute in it or anything, but I want the wife to be able to use it as a back up if something was to happen to one of our daily drivers. I also might try towing a boat or maybe a car trailer every once in a blue moon. Other than that, ITS A BURNOUT MACHINE!!!

From friends I get everything from "leave it alone" to "put a spool in it, or weld the spider gears"

Looking for that good advice I always get here. Maybe even some idea of brands and what I should expect to pay.

Thanks guys and gals

[72armyswbtruck]

Go with a posi rear, it's super better than non posi. As for the ratio try to avoid 4:11's depending on the motor and tranny combo the revs will be super high. I would go with 373's or so they work well for towing and seem to do better on gas mileage.

[boraxman]

I put a Eaton posi in mine with 3.42 gears. Mines a burnout machine too

[409biscayne]

I wouldn't put a spool in it unless it is a drag truck . I have a mini spool in my 68 and its a pita , especially with street tires . ( its not too terrible with slicks)
I bought a new eaton posi unit on ebay for $205 that i'll be installing soon , so i can street drive it more . You might also consider the factory posi , you should be able to find one with 3.73 gears relatively easily .

[DTerry]

Originally Posted by kevncar

...My question is what is the difference...

• Open = The infamous "one wheel squeel" not recommended for a burnout machine, you'll look like a dork.
• Limited Slip - Has clutches to allow one wheel to spin independant of the other. Will try to keep them turning at the same rate until the torque need differs enough to make the clutches slip. Also known as a positraction - but that's really a GM trademarked name (about $400 for an Eaton (non rebuildable)). There's been many names for these by different manufactures - most units use the same princibles.
• Spool - Keeps both wheels turning the same speed ALL of the time. Basically eliminates the "differential" part of the differential. Tires will squeel when manuvering tight turns. If you've got tires that hook up, be sure to get it pointed in the direction you want to go. Recommended for racing applications only (yes, I've run them on the street, and they're lots of fun). You'll get the best looking burnouts with these (about $200).
  Other options under this category with the same effect would include welding the spiders, and mini spools. Welding spiders is very cheap (about $0), get someone experienced at it or you will ruin your rear. Mini spools are not available for all applications (they are for GM 10 and 12 bolts) - you'll need to look around (about $85).
• Other units you didn't mention are lockers, and there are lots of those too, air, non air, etc. They click and are mainly used by off-roaders.($??)

You will need to get someone to 'set up' your gear set if you go with a full spool or a new carrier (posi, eaton, etc.).

Originally Posted by kevncar

...Other than that, ITS A BURNOUT MACHINE!!!

If you've got the money get a LS unit.

(D)

[special-K]

Welded spiders,spool,and locker are all the same results.Both wheel turn all the time.So,the results are maybe too much traction for times like going around a curve or making a turn.The inside wheel needs to spin slower and it won`t.So,it`ll squeal with the least bit of throttle.Drifting through the turns will take care of that.But,limited-slips are made for this reason.They will act like an open differential until one wheel starts to spin.Then the other will lock-in to give a posi effect.To me,the limited-slips are more user friendly.But,with a conscience effort,a posi is a sure-fire way to gain maximum rear traction.

[CochinoFilipino]

Limited Slip Differentials (posi, trac-loc) use clutches. And as the name implies it does slip. How much it slips, depends on how tight it is set-up. And the clutches wear out over time. One thing to consider when buying is if the unit is rebuildable or will it need to be replaced.

An automatic locker (like powertrax) acts as open differential until one wheel starts spinning too fast. Then it Locks up, 100% locked, NO slip. And people are using these in Hot Rods, it's not jus for off-roaders.

Some info here http://auto.howstuffworks.com/differential8.htm

We expect some video after the install.

[special-K]

Auburn Gear makes a real nice unit for the street.I have one in my`90 K/5 with 12.50/33" tires and it`s tough enough for that.

[70c10]

kevncar-I bought my Eaton posi from Toms Differentials.com out in California for $280 3 years ago and it's been good. I recommend them since you live out that way.

[truckdude239]

Originally Posted by kevncar

From friends I get everything from "leave it alone" to "put a spool in it, or weld the spider gears"

welding the spider gears is never a good idea if done wrong would be looking at a bigger repair bill

[409biscayne]

Originally Posted by 70c10

kevncar-I bought my Eaton posi from Toms Differentials.com out in California for $280 3 years ago and it's been good. I recommend them since you live out that way.

I just checked out Toms website , it looks like they also have a store in N. Idaho , close to me I'm calling them monday for axles for my 68 , woo hoo Thanks for the info .

[LONGHAIR]

Whatever you do .......STAY AWAY from the welded spider thing and anyone who recommends doing it. Not only is it bad for the internal parts of your axle, it is very dangerous. .............I'm willing to bet that someone will come in and say "I've had one for years, it's fine, blah blah blah". DON'T DO IT, it will break and at the worst time too.
Also I would stay away from any of the more intense locker type units too. You stated that you need the wife to be able to drive it too, so stick with the more "user friendly" units. That generally means a clutch type unit. Also, have it installed by a professional. You can cost yourself a lot of money trying to do this with-out the experience/know-how. Some will say that you can "get by" with changing carriers as long as you don't change the gears...as long as they are willing to pay for the new parts if it fails.....go for it. Otherwise, it is really better in the hands of a pro.

[Riles72]

How much is a factory .411 12 bolt limited slip from a '68 1/2 ton worth? Anybody know?

[70c10]

Originally Posted by 409biscayne

I just checked out Toms website , it looks like they also have a store in N. Idaho , close to me I'm calling them monday for axles for my 68 , woo hoo Thanks for the info .

I think I paid an extra $25 for bearings and races.

[DTerry]

Just alittle off topic, but still relevant...


<<<<<

That car had welded spiders the first year we ran it, mini-spool after that (full spools are not allowed). Many of these cars have them - BUT, these cars are ALOT safer than street cars. The rears in these cars take way more abuse than anything on the street. It's the gears that get demolished first, not the welded spiders/carriers. Please save the flames for lighting camp fires.

[special-K]

Is that an asphalt car?I thought it was dirt track?Either way,racing is racing and street is street.Honestly,you wouldn`t want a spool or welded spiders on the street for long.And,one thing breaks in the rear,others are effected.I call it the "blender effect".

[DTerry]

Originally Posted by special-K

Is that an asphalt car?I thought it was dirt track?Either way,racing is racing and street is street.Honestly,you wouldn`t want a spool or welded spiders on the street for long.And,one thing breaks in the rear,others are effected.I call it the "blender effect".

Yes - asphalt. Dirt is for farming. Agreed on the racing/street thing, that's why I said alittle off topic (or at least that's what I meant). Also agree about the spool, etc. The one I ran on the street was a pretty serious barely-streetable car. Love the "Blender effect" phrase! Please consider that stolen.

[SSC's76]

When both wheels have traction it reduces the amount of tire shreading time to at least half so keep that in mind.

I like lockers, there cheap, easy to install and effective traction devices that you can do yourself with no special tools or need to measure. It's just slightly more difficult to install then a stock spider assembly. I had sold my powertrax no slip unit a few months back to somone who needed it badly and dident have time to wait for one to be ordered in. The no slip units are nice and rarely make noise but will chirp around corners if you take then tight and fast and once in a while you will hear clicking but it's normal. They sell a Lock Right under the Richmond name and a True Trac under Detriot which costs even less. These are the easyest to install, have the fewest pecies, are stronger IMO and the best part the least expensive peices you can buy. The draw back is they are more agressive and like to click alot with a few strange pops once in a while as the teeth lock and unlock around turns. This is what I ended up with in my 76. The lock right isnt bad in a DD but the no slip is better suited for daily use. Since you use this truck for toy/emergency use I would say the Lock Right would do nicely and is usually $100 cheaper ($320) then the No slip which is $330. Either one will would suit your needs and is just as effective as a spool but safer with less stress on the axles.

[special-K]

D Terry,you have my consent
That`s the only problem with us hillbilly engineers,we have to make up our own names for all that technical stuff.
Dirt`s for farmers?I like that.I guess farmers like it sideways.

[boraxman]

Has anyone tried a ARB air locker? I just put one in my Toyota 4x4. Totally selectable, very cool!

[Swbman]

Definitely spend the extra scratch for limited slip, my son tore his peg leg rear end up housing and all getting wild and crazy with the 383 stroker in his truck...

[SB406]

Just to throw in my $0.02......I just put a Detroit true trac in mine & it is sweet. The true trac is a limited slip unit that behaves like an eaton or auburn. The difference is NO CLUTCHES and NO CLICKING TEETH. It has a helical / planetary gear setup that is pretty slick. If anyone is interrested jump on detroit's web site to see an exploded view.
http://detroitlocker.com/DT.htm

[special-K]

Originally Posted by boraxman

I put a Eaton posi in mine with 3.42 gears. Mines a burnout machine too

That`s what I bought to put in my shortbed.I`ve always been a stump-puller kinda guy,but withfuel costs,I`m going higher.I want to drive it!!I hear these pull just fine.