Transmissions and Drivetrain Need help with your trans? Problems with your axle?

open diff to Posi?

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Old Oct 11, 2010 | 10:53 AM
  #1  
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From: Hamilton, NJ
Car: 1986 Pontiac Firebird
Engine: 357ci 400hp 4BBL
Transmission: 700r4
open diff to Posi?

I have an 86 firebird with open diff and would like to make it a posi, I recently saw some posi units on ebay but they come in both 28 spline and 26 spline. I was thinking that since my car is open then it would have 26 splines. Is this correct? Is a posi unit all that is needed?
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Old Oct 11, 2010 | 11:27 AM
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Re: open diff to Posi?

The 26 spline to 28 spline change was made to both limited slip and open rear ends. 86 would have 26 splines either way.

Most of those Ebay posi's are gov-locks.

Do a search, there's a ton of info on here already... Swapping to a "posi" basically means setting up gears. It's not something most people attempt in their driveway.
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Old Oct 11, 2010 | 12:33 PM
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From: Location, Location!
Car: 92 T/A 'vert
Engine: Mild .040 over L98 4 bolt mains
Transmission: Mostly stock 700R4, 2600 Vigilante
Axle/Gears: LS1 3.42
Re: open diff to Posi?

The easiest way to do this is with a Richmond Powertrax Locker. A little pricey but when compared to not so much the posi carrier but the labor to do the job correctly, (as stated above, not meant for even an accomplished "shadetree" mechanic"), it's cheap and works great. Spend a little time on Google and you can find them on sale cheaper than Summit/Jegs.
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Old Oct 11, 2010 | 01:05 PM
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From: Rochester NY
Car: 1984 z28
Engine: 355
Transmission: 700r4
Axle/Gears: Moser 9" 4.11
Re: open diff to Posi?

If you go the powertrax route make sure you get the "No Slip". Dont get the "LockRite" its a little harsh on the street from what I hear.
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Old Oct 11, 2010 | 06:34 PM
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From: Hamilton, NJ
Car: 1986 Pontiac Firebird
Engine: 357ci 400hp 4BBL
Transmission: 700r4
Re: open diff to Posi?

I don't know alot about this stuff but what is a gov lock. I was also thinking about getting a posi carrier of ebay and getting a mechanic to install it if its cheaper than buying the powertrax that is
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Old Oct 11, 2010 | 07:04 PM
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From: Northern, CA
Car: 1989 Iroc-Z Camaro
Engine: TBI,5.0
Transmission: Automatic 700R4
Axle/Gears: Eaton Posi,3.42,LPW Ultimate Cover
Re: open diff to Posi?

What gear ratio are you running. If you want to go to a different one now would be the time to do it. While your in there. I would not skimp on the rear end. Do it once and be done with it. If you don't want to change the axles to 28 spline and want to stay with a 26 spline carrier and want to go with a higher gear ratio like 3.42 or higher you will need special gears/spacer. I'm not real familiar when it comes to dealing with the 26 spline carrier because I went to the 28 spline axles and 28 spline Eaton carrier when I did my upgrade to 3.42 gears. Not trying to confuse the issue but there's allot to consider when changing over to a "posi". or "no slip" , or "locking" unit. You want to be "happy" with what you have done in the end.

Last edited by Ron U.S.M.C.; Oct 11, 2010 at 07:47 PM. Reason: add info.
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Old Oct 11, 2010 | 07:05 PM
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Re: open diff to Posi?

What is so hard about clicking the "Search this Forum" link? It's in the top right of every sub-forum. Click the box, and fill in the blank for what you want to know about. Type in "Gov lock" and press enter and it will pull up 6 pages of results! Read two or three of those threads and pretty quickly you'll be thinking you REALLY don't want one.

Here's a good example...
https://www.thirdgen.org/forums/tran...lock-posi.html

If you do a search for "convert posi" you'll find threads that tell you all about that too.
Like this one... https://www.thirdgen.org/forums/tran...i-nonposi.html
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Old Oct 11, 2010 | 08:01 PM
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From: Hamilton, NJ
Car: 1986 Pontiac Firebird
Engine: 357ci 400hp 4BBL
Transmission: 700r4
Re: open diff to Posi?

I saw a powertrax 26 spline no slip traction system for sale. Do I install this and my car will be posi or will I have to buy a posi gear like a 3.73 gear?
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Old Oct 11, 2010 | 08:04 PM
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From: Rochester NY
Car: 1984 z28
Engine: 355
Transmission: 700r4
Axle/Gears: Moser 9" 4.11
Re: open diff to Posi?

Just install it in place of your spider gears and you have instant posi.
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Old Oct 11, 2010 | 08:25 PM
  #10  
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From: Hamilton, NJ
Car: 1986 Pontiac Firebird
Engine: 357ci 400hp 4BBL
Transmission: 700r4
Re: open diff to Posi?

but it didn't say anything about any gears and it says no slip.
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Old Oct 11, 2010 | 08:50 PM
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From: Northern, CA
Car: 1989 Iroc-Z Camaro
Engine: TBI,5.0
Transmission: Automatic 700R4
Axle/Gears: Eaton Posi,3.42,LPW Ultimate Cover
Re: open diff to Posi?

If you don't want to change your gears "ring and pinion" you don't have to. They will be used again with that "26" spline Powertrax no-slip unit.
As 84z28 said, Just have it installed and instant posi.Heres a link to the unit at Richmond Gear. = http://www.richmondgear.com/powertrax/noslip.html

Last edited by Ron U.S.M.C.; Oct 11, 2010 at 09:30 PM. Reason: add info.
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Old Oct 12, 2010 | 01:23 PM
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Re: open diff to Posi?

I've got a Lock Right in my S10 truck. I've been driving it every day for 13 years. It works just fine.

If you want to use anything other than the Powertrax kit then you must know what your gear ratio is before you order anything. The Governor Lock is not a good choice. The Eaton Posi is a good choice, but you must have a 3.23 to 4.10 gear to use it. Here is how you install it. http://www.nastyz28.com/forum/showthread.php?t=19773
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Old Oct 12, 2010 | 04:23 PM
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From: Georgetown TX
Car: Base 91 'bird
Engine: 3.1 v6
Transmission: 4L60
Axle/Gears: 9-bolt 3.27 & PBR
Re: open diff to Posi?

I don't see prices on the web site. What's the price range?
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Old Oct 12, 2010 | 04:54 PM
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Re: open diff to Posi?

The Lock Right would be $369.
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Old Oct 12, 2010 | 05:18 PM
  #15  
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From: Rochester NY
Car: 1984 z28
Engine: 355
Transmission: 700r4
Axle/Gears: Moser 9" 4.11
Re: open diff to Posi?

Sometimes ebay has good deals. I got my No Slip brand new and still in the box for $200 plus shipping.
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Old Oct 12, 2010 | 05:21 PM
  #16  
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From: Rochester NY
Car: 1984 z28
Engine: 355
Transmission: 700r4
Axle/Gears: Moser 9" 4.11
Re: open diff to Posi?

Here's an example. But I personally probably wouldnt buy it.

http://cgi.ebay.com/ebaymotors/Power...Q5fAccessories
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Old Oct 12, 2010 | 06:15 PM
  #17  
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From: Georgetown TX
Car: Base 91 'bird
Engine: 3.1 v6
Transmission: 4L60
Axle/Gears: 9-bolt 3.27 & PBR
Re: open diff to Posi?

Big gear head I couldn't open PM. Pop up blocked. I'm new and don't know how to PM yet. Saw it on e-mail. Thanks but no money yet for diff.
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Old Oct 12, 2010 | 06:19 PM
  #18  
Ron U.S.M.C.'s Avatar
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From: Northern, CA
Car: 1989 Iroc-Z Camaro
Engine: TBI,5.0
Transmission: Automatic 700R4
Axle/Gears: Eaton Posi,3.42,LPW Ultimate Cover
Re: open diff to Posi?

I agree that the Eaton is the better choice.Thats what I put in mine. If your going to change the gear to a higher ratio and change out the axles to 28 spline than that's the way to go. If you don't want to mess with the gears ,etc. than I can see were the Powertrax no-slip would be appealing.

Last edited by Ron U.S.M.C.; Oct 12, 2010 at 06:22 PM. Reason: add info.
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Old Oct 12, 2010 | 06:57 PM
  #19  
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From: Rochester NY
Car: 1984 z28
Engine: 355
Transmission: 700r4
Axle/Gears: Moser 9" 4.11
Re: open diff to Posi?

I love my powertrax but If I had another choice I would go with a detroit truetrac in a heart beat.

http://www.eaton.com/EatonCom/Produc...troitTruetrac/
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