Posi Conversion

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Nelson7604

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I have a 1972 Dodge Dart Swinger with a 318 and a 904 transmission.
It still has whatever rear end came stock with a six cylinder and I'd like to upgrade it.
I would like to put a bigger rear end in it and while I'm at it I might as well upgrade to a posi.

How would I go about doing this? Does this involve a new axle and all or is there a conversion kit to use with what I have now?

Thanks!
 
You'll have to find a Chevy rear end to get a posi.
 
Seeing that you have under 40 post here and under the assumption you
could be new to the world of Mopar. Posi is slang for positraction. A term
used by Chevrolet to market their locking differentials.
We all know what you meant as most including myself grew up using the term although
technically incorrect. I still use it alot for the sake of non mopar folks knowing what I am referring to.
Our mopars use the term suregrip. Using the Posi term will ruffle the feathers of some.
You may have known all this already, if not there it is for those who don't.
Anyway, to address your question the 8 3/4 rear axle assembly is the most
popular and desired for a car like what you have. They can be converted to
large bolt pattern if needed. You will need to watch the length when buying.
The 8 1/4 with the large bolt pattern only is also a great choice and somewhat cheaper and easier to find.
The suregrip can be had in both these rear axle types.
Others or a search can fill you in on the non Mopar options that would be the best.
Welcome to the site and glad you got a Mopar. Happy hunting for your axle.
 
ssba said:
They can be converted to
large bolt pattern if needed. You will need to watch the length when buying..
Click to expand...

chances are your 72 has a 5 on 4 bolt pattern (what we call the small bolt pattern)
somewhere around 73 they started using 5 on 4.5 (large bolt pattern)

it would be preffered to keep the same bolt pattern all the way around but not biggy if you don't
keep in mind that if your car has drum brakes up front and you wish to convert to discs later you will most likely end up with large bolt pattern disc brakes


now, when your told to "watch the length" he means that a 8 3/4 rear end for a B body will have longer axle tubes and the spring perches in a different place then a 8 3/4 rear end for a A body
it can be made to fit, for sure, but it will take some modifying
the one exception being the early B bodies (what was it, 65-67?) they should still need to have the spring perches moved but are only marginally wider and will fit even with stock A body backspacing on your wheels (though they will fill the wheel wells better)
 
Nelson7604 said:
I have a 1972 Dodge Dart Swinger with a 318 and a 904 transmission.
It still has whatever rear end came stock with a six cylinder and I'd like to upgrade it.
I would like to put a bigger rear end in it and while I'm at it I might as well upgrade to a posi.

How would I go about doing this? Does this involve a new axle and all or is there a conversion kit to use with what I have now?

Thanks!
Click to expand...

I'd assume it has the small rear. Upgrading could be going to a A or B body 8.75 or dana.

YOu could also just order one. I'd go that route. by the time you get a stock rear, add big blot pattern axles, new brakes, pretty it up and make it road ready you'll have a lot of time and money into it.

I'd go with a new dana from strange and get an S-trac diff. (worm gear posi) This is cheapest route and you'll never break it.
 
That makes sense. I have heard "posi" and "suregrip" but never knew the difference. Now that I know that, I can probably find one online a little easier. Ha! Thanks for the information.
 
Way back when there were many different names used by the different manufacturers to market that style of differential, just as there was a lot of different names used for marketing V-8 engines. Some of the names used include suregrip, positraction, twin traction, twin grip, powrlok, saf-t-track, tracloc, and just plain limited slip.
 
And, if, the engine is to stay a normally aspirated teener, a properly set up 8.25 will last you for many, many miles, and years. Swapping ratios however is not a quick thing. Better it is, to have a second complete rear end, brakes and all,set up,and waiting to go.
 
67redcudavert said:
Some of the names used include suregrip, positraction, twin traction, twin grip, powrlok, saf-t-track, tracloc, and just plain limited slip.
Click to expand...

They are all limited slips, however the names do in some cases have differences of the way they perform that operation, as above has limited slip terms mixed in with limited slip types.

I'll only deal with what applies here, otherwise this post will be about a 90 minute read...


The sure grip is the fancy word for limited slip by Mopar for their cars, then Positraction in chevy, Anti-Spin at olds, Safe-T-Track in pontiacs, Positive Traction in buicks, Twin-Grip in AMCs, ford Equa-Lok or Traction-Lock.

Dana uses powr lok, trac lok to differentiate between the 2 spider clutch style pack and the 4 spider ramping style clutch pack (among other styles from electric to hydro and air).
Eaton uses positraction for its spring style clutch pack and True track for its helical style (eaton has other styles also mechanical, eltectric)
Borg Warner uses Spin-Resistant (you know as cones or auburn)

.

.
 
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