Limited Slip To Posi - The 1947 - Present Chevrolet & GMC Truck Message Board Network

twitch4187 · 04-27-2005, 01:57 PM

Ok here's the deal I bought a 68 Chevy Stepside about a week ago. I know it has a limited slip rear end but I want a posi unit. I plan to swap the engine to a 383 stroker and I need it to be strong. Do I need another posi axle or will a Detroit Locker or Eaton Locking unit work? Does anyone know the part numbers or where I can get these lockers? I have to be able to order from the internet since I am currently deployed in Iraq.

FirstGen · 04-27-2005, 02:04 PM

a limited slip is commonly referred to as a "posi". The Eaton unit you are talking about are limited slip units and the detroit locker is actually a locking diff. If you are wanting to upgrade to a newer and stronger limited slip unit I would reccomend the Eaton. It is very durable with it forged spider gears and heavy springs and carbon clutches. It is also fully rebuildable with several upgrades. You can get them through Jegs or Summit or also find them online on ebay and such.
Goodluck and WELCOME!!!

Purs · 04-27-2005, 02:05 PM

limited slip is just another term for positrac. Lockers on the other hand are different. Check out this site for good info:

http://randysringandpinion.com/conte...lt.asp?pid=128

just noticed that FirstGen beat me to it!

FirstGen · 04-27-2005, 02:10 PM

haha I win

Purs · 04-27-2005, 02:23 PM

you must have been "on the juice"!

twitch4187 · 04-27-2005, 02:35 PM

great info guys. Would an ARB Air Locker stand up to the punishment in your opinions?

Purs · 04-27-2005, 02:40 PM

I'm with FirstGen, I'm going through my 12 bolt right now and I chose the new Eaton Unit. The internals are darn near bulletproof AND rebuildable if you do happen to trash it....

I have no experience or knowledge about the air lockers.

twitch4187 · 04-27-2005, 02:44 PM

Thanks guys I'll look into the eaton unit.

smokekiki · 04-27-2005, 02:55 PM

Quote:

Originally Posted by twitch4187

great info guys. Would an ARB Air Locker stand up to the punishment in your opinions?

I have seen ARB's take some punishment without failing.

Jason915 · 04-27-2005, 03:03 PM

http://cgi.ebay.com/ebaymotors/ws/eB...spagename=WDVW

This locker is awsome for traction and very tuff, I broke an axle shaft with this locker and the locker held up just fine.

CHEVIBUBBA · 04-27-2005, 05:49 PM

the airlocker will hold up beyond what the rear will take if install is correct.
according to peyton performance in waxahachie TX. the truck 12 bolts will hold up pretty good into the 13's.the pinion gear shaft is smaller than the car 12 bolt,(why?),so much more than that & it's KABOOM!

FirstGen · 04-27-2005, 06:09 PM

Quote:

Originally Posted by CHEVIBUBBA

the airlocker will hold up beyond what the rear will take if install is correct.
according to peyton performance in waxahachie TX. the truck 12 bolts will hold up pretty good into the 13's.the pinion gear shaft is smaller than the car 12 bolt,(why?),so much more than that & it's KABOOM!

Actually the pinion shaft is not the weak link. These truck rears have seen many many cars/trucks in the 10's and even 9's. The weak point in the Chevy 12 bolt/14 bolt design is actually the contact pattern on the ring gear. With more than around 750 horse you will actually strip the ring gear teeth off the ring gear. Remember that the pinion is a very short piece of metal and quite large in comparison to say your input shaft on your tranny which is smaller in diameter and longer to boot. Another point is that the pinion is being applied before you multiply torque because of the actual ratio.

Many board members have been into the 11's on the truck rear, myself included.

FirstGen · 04-27-2005, 06:11 PM

Quote:

Originally Posted by Jason915

http://cgi.ebay.com/ebaymotors/ws/eB...spagename=WDVW

This locker is awsome for traction and very tuff, I broke an axle shaft with this locker and the locker held up just fine.

I destroyed one of these... They also do very weird things in race applications. Say you get some wheel hop, these have a tendency to un-lock on you. I think the Eaton is the best bang for the buck...

BubbaGreen · 04-27-2005, 06:16 PM

I went with an EATON as well....3.73gears in the stock 12bolt axle.

CHEVIBUBBA · 04-27-2005, 07:26 PM

Quote:

Originally Posted by FirstGen

Actually the pinion shaft is not the weak link. These truck rears have seen many many cars/trucks in the 10's and even 9's. The weak point in the Chevy 12 bolt/14 bolt design is actually the contact pattern on the ring gear. With more than around 750 horse you will actually strip the ring gear teeth off the ring gear. Remember that the pinion is a very short piece of metal and quite large in comparison to say your input shaft on your tranny which is smaller in diameter and longer to boot. Another point is that the pinion is being applied before you multiply torque because of the actual ratio.

Many board members have been into the 11's on the truck rear, myself included.

realy!thats my dream!actually, it's 10's but....
ever hear of a LWB doin 11's?
how much did yours weigh when you broke into the 11's?
guess i need to get the lowdown on your truck!
good to know it's been done on the stock 12bolt.
i stripped a ring gear last year.not 750 horses though.about 450.
more due to wear than power i think.

FirstGen · 04-27-2005, 08:54 PM

I weighed in at 3600# with out me in it. This was before I chopped it down to a short wheel base. It takes about 750 horsepower and 3500# to strip the teeth on a new set of Motives or GM gears - being tight and properly set up is a must. After that you can go to the pro series gears but you can't run them on the street because the will wear out quickly.
I went 7.50's on 125 shot when I was long wheel base. That's mid/high 11's. It should do that on the motor now and 7.0's or 6.90's on the spray...

jamesi20 · 04-27-2005, 09:00 PM

You should maybe look into the TRUETRAC it is a gear driven limited slip that from everything I have read and seen is basically bullrt proof.I had one put in my 12 bolt by a guy (John Peto) who is a NHRA record holder and he swears by them.They are very street freindly and according to John lock up good at the strip.just my .02worth

www.tractech.com

04-27-2005, 01:57 PM	#1
twitch4187 Registered User Join Date: Apr 2005 Posts: 23	Limited Slip To Posi Ok here's the deal I bought a 68 Chevy Stepside about a week ago. I know it has a limited slip rear end but I want a posi unit. I plan to swap the engine to a 383 stroker and I need it to be strong. Do I need another posi axle or will a Detroit Locker or Eaton Locking unit work? Does anyone know the part numbers or where I can get these lockers? I have to be able to order from the internet since I am currently deployed in Iraq.

04-27-2005, 02:04 PM	#2
FirstGen Just Don't Stop! Join Date: Feb 2004 Location: Dallas Posts: 1,239	a limited slip is commonly referred to as a "posi". The Eaton unit you are talking about are limited slip units and the detroit locker is actually a locking diff. If you are wanting to upgrade to a newer and stronger limited slip unit I would reccomend the Eaton. It is very durable with it forged spider gears and heavy springs and carbon clutches. It is also fully rebuildable with several upgrades. You can get them through Jegs or Summit or also find them online on ebay and such. Goodluck and WELCOME!!! __________________ 1968 C10 build in process TT LSA/6L90e/9"

04-27-2005, 02:05 PM	#3
Purs Got Big Block? Join Date: Apr 2000 Location: West Texas Posts: 1,510	limited slip is just another term for positrac. Lockers on the other hand are different. Check out this site for good info: http://randysringandpinion.com/conte...lt.asp?pid=128 just noticed that FirstGen beat me to it! __________________ "Experience is what you get when you didn't get what you wanted." Last edited by Purs; 04-27-2005 at 02:06 PM.

04-27-2005, 02:10 PM	#4
FirstGen Just Don't Stop! Join Date: Feb 2004 Location: Dallas Posts: 1,239	haha I win __________________ 1968 C10 build in process TT LSA/6L90e/9"

04-27-2005, 02:23 PM	#5
Purs Got Big Block? Join Date: Apr 2000 Location: West Texas Posts: 1,510	you must have been "on the juice"! __________________ "Experience is what you get when you didn't get what you wanted."

04-27-2005, 02:35 PM	#6
twitch4187 Registered User Join Date: Apr 2005 Posts: 23	great info guys. Would an ARB Air Locker stand up to the punishment in your opinions?

04-27-2005, 02:40 PM	#7
Purs Got Big Block? Join Date: Apr 2000 Location: West Texas Posts: 1,510	I'm with FirstGen, I'm going through my 12 bolt right now and I chose the new Eaton Unit. The internals are darn near bulletproof AND rebuildable if you do happen to trash it.... I have no experience or knowledge about the air lockers. __________________ "Experience is what you get when you didn't get what you wanted." Last edited by Purs; 04-27-2005 at 02:42 PM.

04-27-2005, 02:44 PM	#8
twitch4187 Registered User Join Date: Apr 2005 Posts: 23	Thanks guys I'll look into the eaton unit.

04-27-2005, 03:03 PM	#10
Jason915 Registered User Join Date: Jan 2005 Location: Colorado Springs Posts: 693	http://cgi.ebay.com/ebaymotors/ws/eB...spagename=WDVW This locker is awsome for traction and very tuff, I broke an axle shaft with this locker and the locker held up just fine. __________________ 1971 GMC K1500 SWB Fleetside, 4" skyjacker softride and, 14 Bolt FF, HD Dana 44 4.10's 1970 K5 TBI conversion lifted etc SOLD 1968 C20 camper truck SOLD “To ban guns because criminals use them is to tell the innocent and law-abiding that their rights and liberties depend not on their own conduct, but on the conduct of the guilty and the lawless.” Jeff Snyder

04-27-2005, 05:49 PM	#11
CHEVIBUBBA got boost? Join Date: Mar 2005 Posts: 123	the airlocker will hold up beyond what the rear will take if install is correct. according to peyton performance in waxahachie TX. the truck 12 bolts will hold up pretty good into the 13's.the pinion gear shaft is smaller than the car 12 bolt,(why?),so much more than that & it's KABOOM! __________________ '70 chevy lwb w/'67 hood. 357 s.b.c. built, 4l60 w/vigilante lockup high stall converter, edelbrock pro-flo,brodix heads,comp cams rollerized w/ belt drive, one piece d-shaft, yada, yada, yada..... '82 honda v45 sabre"the black"

04-27-2005, 06:16 PM	#14
BubbaGreen Senior Member Join Date: Mar 2001 Location: Cedar Park, TX Posts: 686	I went with an EATON as well....3.73gears in the stock 12bolt axle. Attached Images __________________ 71 Chevy C-10 SWB Fleetside RamJet-350/4L60e & Compushift/3.73Posi See it at www.prismnet.com/~grzanich

04-27-2005, 08:54 PM	#16
FirstGen Just Don't Stop! Join Date: Feb 2004 Location: Dallas Posts: 1,239	I weighed in at 3600# with out me in it. This was before I chopped it down to a short wheel base. It takes about 750 horsepower and 3500# to strip the teeth on a new set of Motives or GM gears - being tight and properly set up is a must. After that you can go to the pro series gears but you can't run them on the street because the will wear out quickly. I went 7.50's on 125 shot when I was long wheel base. That's mid/high 11's. It should do that on the motor now and 7.0's or 6.90's on the spray... __________________ 1968 C10 build in process TT LSA/6L90e/9"

04-27-2005, 09:00 PM	#17
jamesi20 Senior Member Join Date: May 2002 Location: NORTHEAST OHIO Posts: 493	You should maybe look into the TRUETRAC it is a gear driven limited slip that from everything I have read and seen is basically bullrt proof.I had one put in my 12 bolt by a guy (John Peto) who is a NHRA record holder and he swears by them.They are very street freindly and according to John lock up good at the strip.just my .02worth www.tractech.com



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