Positraction rear end

[dstuff5]

Will a positraction rear end from a 56 chevy bolt in my 73 Avanti? Anybody have any ideas?

[WayneC]

I cannot claim any expertise in this area, but here are my thoughts...

The rear axle in your Avanti is likely a Dana 44 unit. I doubt that the 56 Chevy used a Dana 44, and if it did, that it would simply bolt into an Avanti.

(Dana is a company headquartered in Detroit that manufactured differentials for various auto makers, and the 44 is a design they probably supplied in various configurations... axle housing lengths, spline count, spring mounts, traction bar mounts, lug sizes, etc depending on the application, but the basic dimensions of the differential gearbox should be standard, I think).

http://www.studebaker-info.org/text3/Dana3.txt

http://forum.studebakerdriversclub.com/showthread.php?33130-Converting-a-Dana-44-to-PosiTrac

http://www2.dana.com/pdf/X510-7.pdf

http://www.aoai.org/forums/index.php?showtopic=306

There are suppliers offering positraction units for Dana 44 axles...

https://www.yukongear.com/PartsList.aspx?SearchMode=Diff&Type=Dana&DiffID=135&DiffName=Dana+44+Rear&CatID=38&CatName=Posi+%2F+Positractions

http://www.nitro-gear.com/positractions/

Or, it might be possible to find a dana 44 axle for another application (dunno if 1956 Chevy fills that bill) that can be adapted... chances are that the

mounts and axle-axle width and axle length may differ from the Avanti.

Your best bet might be to visit a shop that specializes in servicing differentials and see what they'd recommend.

[popeyesteve]

With enough will power and money, just about anything can be adapted to anything else. The factory rear end for the 1955-1957 Chevy is a third member type. The third member was used until 1964, but the housings and axles are unique for different years (leaf vs. coil springs, body/axle width). It is not a particularly strong rear end. The wheel pattern is 5x4-3/4, whereas the Avanti uses Ford/Chrysler pattern 5x4-1/2, so you would have mixed wheels on your car. Don't switch rear ends just because you happen to have a good '56 Chevy one laying around. If you have your original Dana 44 Avanti rear, don't cut off the spring perches and traction bar mounts. It would be MUCH preferable to put in a Twin-Track, Eaton posi or Detroit TruTrac differential unit. Sell the Chevy rear and buy one of these differential options. I went through this last year, replacing an oddball Chrysler rear end that a previous owner had switched with a real Avanti Dana 44. Much better and the width will be correct.

Steve