Pros and Cons of change to Posi rear? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

C10Silverado79 · 04-13-2010, 03:13 PM

I have a standard rear in my truck noticed a 5-LUG Posi Rear on CL. It got me wondering what the Pros and Cons are to swapping for a Posi?

grmrepr · 04-13-2010, 03:48 PM

I think a big pro would be that you will have both tires spinning so you will have better traction

68Timber · 04-13-2010, 04:05 PM

There's no downside I know of...

87chevy.com · 04-13-2010, 06:53 PM

Quote:

Originally Posted by BRUISER

There's no downside I know of...

you will be purchasing sets of rear tires v.s. one tire for the rear

camshaftgsxr · 04-13-2010, 10:26 PM

Quote:

Originally Posted by 87chevy.com

you will be purchasing sets of rear tires v.s. one tire for the rear

i thought that was a pro?

JR0187 · 04-13-2010, 04:25 PM

The only one I know of is when making turns, one wheel needs to spin faster than the other. I don't know what the side effects of this is though. But I would probably say the pros out weigh the cons .

ont_guy_38 · 04-13-2010, 05:28 PM

The only con I can think of is if you are driving on snow and it spins it has a tendancy to slide sideways because you have both wheels spinning which can cause some problems sometimes, other then that there is just the special additive you have to buy for them

LONGHAIR · 04-13-2010, 07:54 PM

Quote:

Originally Posted by ont_guy_38

The only con I can think of is if you are driving on snow and it spins it has a tendancy to slide sideways because you have both wheels spinning

This can happen in the rain too, especially if you have a lead foot.
The biggest "downside" is the cost of adding it versus the "benefit" of it being there. Everyone does not need a posi-traction unit and it's not like it is ever going to "pay for itself" like some add-on the increases fuel mileage.

INSIDIOUS '86 · 04-13-2010, 09:45 PM

with a posi you wont have right tire fire when going around every corner in the rain, also an open diff is more prone to snap steer than a posi, when you turn left your left tire can unload very suddenly and send you into a 180 or worse, but with a posi you will know when your rear starts kicking aout immediatly, there are quite a few pros to switching over, it all depends on how you use your truck. will you benifit from the extra traction or not?

harnalien · 04-13-2010, 10:04 PM

I feel like there was just a little less power off the line, just slight. However, I have a "poor man's posi." I don't konw if that makes a difference or not.

**nlped** · 04-13-2010, 11:12 PM

Every single square I have owned has been swapped to a posi...or is in the process of getting one. Once you get stuck in somebodies front yard after a rain, you'll always put one it

C10Silverado79 · 04-13-2010, 11:36 PM

I was thinking about it for the snow and for the occasional boat launch. Just not sure if it's worth the cost and work. I also know squat about drive trains. Is it better to swam axles or to put new gears in the existing axle? If what I have read recently is accurate, I have a 12 bolt rear. I have no clue what the ratio is.

**nlped** · 04-14-2010, 07:45 AM

The '76 Blazer I have also has a 12 bolt under it, and it is about to get an Auburn, new 3.42 gears and all new bearings. I, too, really need the posi most when lauching/pulling the boat in/out of the water. But it is a nice reassurance to know that if a situation comes up, both tires are going to pull

.

As far as I.D.ing your rearend type, just lay under the rear and count the number of bolts holding the rearend inspection cover to the housing. It will either be 12 or 10, matter of fact, if there is only one bolt at 6 o'clock it's a 10 bolt, but if there are 2 bolts parallel at the bottom of the cover it's a 12 bolt. That will at least get you on course for knowing which rearend you actually have.

C10Silverado79 · 04-14-2010, 08:50 AM

Quote:

Originally Posted by nlped

The '76 Blazer I have also has a 12 bolt under it, and it is about to get an Auburn, new 3.42 gears and all new bearings. I, too, really need the posi most when lauching/pulling the boat in/out of the water. But it is a nice reassurance to know that if a situation comes up, both tires are going to pull

.

I was under the truck this past weekend replacing the whole brake system. I counted 12 bolts on the cover. Are you putting in a whole new axle or new parts in your existing axle? Like I said, I know virtually nothing about rear ends and transmissions so I'm not sure what an Auburn is.

**nlped** · 04-14-2010, 04:33 PM

Quote:

Originally Posted by C10Silverado79

I was under the truck this past weekend replacing the whole brake system. I counted 12 bolts on the cover. Are you putting in a whole new axle or new parts in your existing axle? Like I said, I know virtually nothing about rear ends and transmissions so I'm not sure what an Auburn is.

I am just replacing the parts in my existing housing. I have an Auburn, a new set of 3.42 gears (replacing the existing 3.08ish gears with a bit lower gear in anticipation of an LSX swap in the near future) and all new bearings and seals.

Now, understand, I'm not actually replacing them. I found a guy who builds and races round track cars, and does this kind of work as well. He is charging me $75 and guarantees the correct fit and finish. He has already done 2 sets for me, and they both worked perfectly.

**N2TRUX** · 04-14-2010, 10:21 PM

Quote:

Originally Posted by nlped

....... I found a guy who builds and races round track cars, and does this kind of work as well. He is charging me $75 and guarantees the correct fit and finish......

Hmm? How far is it from Texas to Alabama and back again?

**nlped** · 04-15-2010, 08:12 AM

Quote:

Originally Posted by N2TRUX

Hmm? How far is it from Texas to Alabama and back again?

Lol! When I moved to Alabama, it was from Denton, Tx. I left behind a bunch of friends, so I made the trip quite often. I got it down to 10 hours each way

Now understand that I will be taking him just the rearend out of the truck. Since I will be lowering the Blazer via a flip, new shocks, c-notch, upgrading the brakes, and the u-joints probably need attention, I will just pull the whole thing and have him bench build it.

James McClure · 04-14-2010, 10:12 AM

York, you live in the "snow belt" just like I do. Seeing as yours isn't 4WD I would swap rear axels and be done with it. You don't want to tangle a$%holes with trying to swap parts around inside an axel unless you know what your doing, trust me. Every rear axel is different, even 2 going down the assembly line one after the other. Pinion depth, ring gear backlash\clearance, bearing preload, not to mention bearing replacement. It's a lot of work thats sometimes very tedious and sometimes frustrating. Get it wrong and she will howl something awful, and possibly destroy itself. I did it for 33 years and have a Detroit locker posi unit sitting in my garage I was going to install but the work involved dosen't justify changing from an open rear because I have 4WD. Jim

04-13-2010, 03:13 PM	#1
C10Silverado79 Registered User Join Date: Feb 2010 Location: York, PA Posts: 180	Pros and Cons of change to Posi rear? I have a standard rear in my truck noticed a 5-LUG Posi Rear on CL. It got me wondering what the Pros and Cons are to swapping for a Posi? __________________ 1979 C10 Silverado 1998 Camry 5spd 2005 Harley ElectraGlide

04-13-2010, 03:48 PM	#2
grmrepr Registered User Join Date: Sep 2009 Location: Poteau, Oklahoma Posts: 127	Re: Pros and Cons of change to Posi rear? I think a big pro would be that you will have both tires spinning so you will have better traction __________________ "First off I'm an OKIE.... so don't call me Tex!" 1985 Chevy C-10 SWB 305 looking for posi rearend 2003 GMC Sonoma (DD) 1999 GMC Sierra 4x4 327 (Out Of Commission) 1999 Pontiac Grand Prix GTP Supercharged 2004 Chevy Malibu (Wife's Hot Rod) Last edited by grmrepr; 04-13-2010 at 03:48 PM.

04-13-2010, 04:05 PM	#3
68Timber I know the pieces fit Join Date: Nov 2007 Location: MONTGOMERY, AL Posts: 5,523	Re: Pros and Cons of change to Posi rear? There's no downside I know of... __________________ John 79 2wd Blazer (Bruiser) 85 M1009 Blazer (Sarge) build 74 Honda Z50 build

04-13-2010, 04:25 PM	#6
JR0187 Registered User Join Date: Mar 2010 Location: Piedmont, AL Posts: 49	Re: Pros and Cons of change to Posi rear? The only one I know of is when making turns, one wheel needs to spin faster than the other. I don't know what the side effects of this is though. But I would probably say the pros out weigh the cons .

04-13-2010, 05:28 PM	#7
ont_guy_38 Registered User Join Date: Jul 2007 Location: Ontario Canada Posts: 1,006	Re: Pros and Cons of change to Posi rear? The only con I can think of is if you are driving on snow and it spins it has a tendancy to slide sideways because you have both wheels spinning which can cause some problems sometimes, other then that there is just the special additive you have to buy for them

04-13-2010, 09:45 PM	#9
INSIDIOUS '86 Registered User Join Date: Jul 2009 Location: washington Posts: 4,178	Re: Pros and Cons of change to Posi rear? with a posi you wont have right tire fire when going around every corner in the rain, also an open diff is more prone to snap steer than a posi, when you turn left your left tire can unload very suddenly and send you into a 180 or worse, but with a posi you will know when your rear starts kicking aout immediatly, there are quite a few pros to switching over, it all depends on how you use your truck. will you benifit from the extra traction or not?

04-13-2010, 10:04 PM	#10
harnalien TruckincrazY Join Date: May 2004 Location: Haslet, TX Posts: 493	Re: Pros and Cons of change to Posi rear? I feel like there was just a little less power off the line, just slight. However, I have a "poor man's posi." I don't konw if that makes a difference or not.

04-13-2010, 11:12 PM	#11
nlped Senior Member Join Date: Jul 2009 Location: Hayden, Al. Posts: 4,148	Re: Pros and Cons of change to Posi rear? Every single square I have owned has been swapped to a posi...or is in the process of getting one. Once you get stuck in somebodies front yard after a rain, you'll always put one it __________________ Carter 1968 Chevy SWB Fleet... Walt 1963-1/2 Ford Falcon Futura...Martha

04-13-2010, 11:36 PM	#12
C10Silverado79 Registered User Join Date: Feb 2010 Location: York, PA Posts: 180	Re: Pros and Cons of change to Posi rear? I was thinking about it for the snow and for the occasional boat launch. Just not sure if it's worth the cost and work. I also know squat about drive trains. Is it better to swam axles or to put new gears in the existing axle? If what I have read recently is accurate, I have a 12 bolt rear. I have no clue what the ratio is. __________________ 1979 C10 Silverado 1998 Camry 5spd 2005 Harley ElectraGlide

04-14-2010, 07:45 AM	#13
nlped Senior Member Join Date: Jul 2009 Location: Hayden, Al. Posts: 4,148	Re: Pros and Cons of change to Posi rear? The '76 Blazer I have also has a 12 bolt under it, and it is about to get an Auburn, new 3.42 gears and all new bearings. I, too, really need the posi most when lauching/pulling the boat in/out of the water. But it is a nice reassurance to know that if a situation comes up, both tires are going to pull . As far as I.D.ing your rearend type, just lay under the rear and count the number of bolts holding the rearend inspection cover to the housing. It will either be 12 or 10, matter of fact, if there is only one bolt at 6 o'clock it's a 10 bolt, but if there are 2 bolts parallel at the bottom of the cover it's a 12 bolt. That will at least get you on course for knowing which rearend you actually have. __________________ Carter 1968 Chevy SWB Fleet... Walt 1963-1/2 Ford Falcon Futura...Martha

04-14-2010, 10:12 AM	#18
James McClure One shot, one kill. Join Date: Dec 2007 Location: Saratoga Springs NY Posts: 859	Re: Pros and Cons of change to Posi rear? York, you live in the "snow belt" just like I do. Seeing as yours isn't 4WD I would swap rear axels and be done with it. You don't want to tangle a$%holes with trying to swap parts around inside an axel unless you know what your doing, trust me. Every rear axel is different, even 2 going down the assembly line one after the other. Pinion depth, ring gear backlash\clearance, bearing preload, not to mention bearing replacement. It's a lot of work thats sometimes very tedious and sometimes frustrating. Get it wrong and she will howl something awful, and possibly destroy itself. I did it for 33 years and have a Detroit locker posi unit sitting in my garage I was going to install but the work involved dosen't justify changing from an open rear because I have 4WD. Jim __________________ 1984 K20 350M engine with 465,000 miles. Well, it's finally done!! Almost 2 years of work, but it was really worth the effort. Little stuff left to do is mount winch, wet sand & buff out and build belly pan\running boards. Body work takes lots and LOTS of beer!!!! God, Guts and Guns made America and God, Guts and Guns will preserve it! The worst thing you could do is get into my sights, but that don't matter, you'll never know it, cause you'll never hear the shotJim or Paladin whichever you choose.



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