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Old 12-25-2005, 12:42 PM
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posi-install question?

Hi everyone, I have a question on the 10 bolt rear end that is in my son's '56 chevy pickup. We had the differential rebuilt last summer and went from 391 down to 308 gears...for the obvious gas mileage help. It has a 350/350 combo with all kinds of goodies Anywho, the guy that rebuilt the rear told me when we picked it up that it does not have a posi in it, but has a minispool type deal that locks the axles. So I opened her up a couple of weeks ago to remove that and it has 4 blocks that lock together, no spider gears. So I could not remove the blocks because of the lack of spider gears to work the differential. Well, he wants to add a posi from Summit racing. The question is: Will the posi take the place of the spider gears, just like the blocks that are in there now? I won't need spider gears if I get the posi, is what I am really asking??? I know that locking the axle together is very bad for street driving, causes the tires to squeal on a turn instead of being differentiated...what a word....Thanks..gary.
Here's some pics of his pickemuptruck. He is very proud of it, he went out at 14 yrs old and found this with no motor/tranny and then helped me build the whole thing. He went and found the camaro front clip so it has pwr steering/disc brakes and drives great, except for this last little detail in the rear.
http://www.freewebs.com/gwstang/56truckpics.htm

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Old 12-25-2005, 01:23 PM
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Squeeling tires is the least of the problems. Dangerous handling especially in the wet is the major concern.

Obviously a posi is different than your "mini-locker".... yours is probably by PowerTrax, the way you describe it, which replaces the axle gears with 4 thick disks with teeth, but it still applies power through the spider gear drive shaft/pin inside your factory carrier. Hence the term "mini".

Full locker or "Detroit Lockers"..... is a complete carrier assembly that drives the locker "gears" not by a shaft but by the carrier itself. very strong.

Spools actually lock the axles solid together all the time, and a

mini-spool still drives the spool/axles by using the spider shaft. "mini" They fit inside of the factory carrier.

A full spool is a complete carrier that drives the axles by the "gear" latching into the carrier itself, not by being driven by a shaft... very strong.

When you buy a posi unit,,,, whichever brand or type,,, you will be buying the entire carrier assembly with its guts ready to accept the axles, and you will be installing your old ring gear onto the new carrier assm. and installing new carrier bearings. At least your pinion depth won't have to be changed since the relationship of the pinion gear to the ring gear will not be changed.

I am leaning toward the benefits of the Thorsen screw type that is suppose to be smoother, stonger, and longer lasting than a plain clutch disk or cone type posi.

This site might help your understanding the different types.

http://www.currieenterprises.com/ces...nyhistory.aspx

http://www.peytonperformance.com/sto...ef=LimitedSlip

Last edited by xntrik; 12-25-2005 at 02:04 PM.
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Old 12-26-2005, 10:30 AM
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btw. going from a 391 down to a 308 doesn't mean that you will get better gas milage. in fact, if you drive just around town. your milage will go lower. why ? because you have to give it more throttle to compensate for the lack of leverage the 308 has over the higher leverage the 391 has.

now. if you drive pretty much always on the highway, 55mph and up. then yes, a little higher milage will be gotten.
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Old 12-26-2005, 06:56 PM
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Hey, thanks for the posi info an links. He is looking at a Detroit locker right now. It's a nice truck so it deserves the best!
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Old 12-26-2005, 07:02 PM
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Hey Vortx, we live way out in the sticks so it's a good 30 mile ride when he leaves in the truck. He does get a little better mileage with the 308. The old gears were very worn out and had a lot of slop so we had to do something and seemed like a good option for new gears. One plus was the tranny would now downshift into passing gear when called upon. Could not do it before, guess the high gears kept the rpm's way up. With the new gears, it's no problemo!
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Old 12-26-2005, 10:57 PM
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[QUOTE=gwstang]
I know that locking the axle together is very bad for street driving, causes the tires to squeal on a turn instead of being differentiated...what a word....Thanks..gary.

gwstang Hey, thanks for the posi info an links. He is looking at a Detroit locker right now. It's a nice truck so it deserves the best!

QUOTE]

Sir, a Detroit locker or similar will make it dangerous as hell to drive on wet or slippery roads..... It will try to push the front end straight off the curves... or spin you out. It also jerks like hell when engaging and unlocking. They are basicly for street driven race cars or off roading.
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Old 12-27-2005, 07:58 AM
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I thought the "lockers" unlocked and gave normal performance going around curves etc. I have heard they were rough on icy roads because of the slipping. Doesn't get icy very often way down here, only about every 7 or 8 yrs do we get an ice storm. People go nuts, wrecks everywhere so I don't think he would be driving his '56 in those conditions...
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Old 12-27-2005, 05:12 PM
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Quote:
Originally Posted by gwstang
I thought the "lockers" unlocked and gave normal performance going around curves etc. I have heard they were rough on icy roads because of the slipping. Doesn't get icy very often way down here, only about every 7 or 8 yrs do we get an ice storm. People go nuts, wrecks everywhere so I don't think he would be driving his '56 in those conditions...

"Normal" performance in a curve..... absolutely NOT.

If it is rainy it is dangerous.... Just wait until the first time you end up in somebody's front lawn or ruin a front tire, wheel, and A frame on a curb in the rain.. Been there, done that.

Lockers are either locked or open. PERIOD... there is NO LIMITED SLIP. They lock and unlock abruptly and often unexpectedly. When they unlock, the outside axle turns faster than the inside axle which can never turn slower than the carrier. If you get pushing in a turn and get off the gas, the locker pops out, and the car will abruptly turn in. Depending upon the severity and the wetness, the car could spin out. If you are in a turn and apply any power whatsoever the locker will lock.

I know too many people who have tried them.

I feel like I am being redundant here.
Suit yourself..... but I bet that you will end up selling it for half what you paid.
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