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Tech Question

Dick Scaife,, Perth, Western Australia, 70 Valiant VG 2 Door 383

Mr. Ehrenberg, Hi, I just found a diff, looks like a Dana,but I think it’s a small one (not a 60). The housing numbers are 48674 -3723599, preceded by a Pentastar and 10 – 05 (in a circle) – 78. The ringgear has a bunch of numbers, but I think it’s a 2.45 ratio? It’s an opencentre diff and the axles look like they are held in by a clip on the end inthe centre section. The perch distance is 44-1/2″ centre to centre, so Iwonder what it came out of? Also, can you tell me if there are ring/pinionsets for it and Sure Grip assemblies, and would it be strong enough tohandle 500+ HP through a 727 in a light A body car on the strip? I will tryto send a couple pics to you email address. Appreciate your help on this,Thanks, Dick Scaife, Perth, Western Australia.

Dick-

It is a Chrysler-built 8.25″ axle. (Think about it – why would the Pentastarbe on a Dana axle?) Absolutely nothing wrong with it, very easy to service,lots of parts available, cheap, production just ended very recently (infact, if Chrysler survives, it may continue production). It is, however, not”up to” a healthy big block. The factory never used it in anything morepotent than a 383 2-Bbl.

With that perch width, your axle is out of an F/J/M-body.

Chrysler also builds a 9.25″ version, which is plenty beefy and would do thejob, should you find one. (Send me some more of those awesome Aussie riblamb chops I ate last night and we’ll talk….) However, no factory 9.25″ isnarrow enough for an A-body, so it would need to be narrowed and customaxles procured. (The only exception might be one from a Grand Cherokee,which I don’t have specs for).

In case you do some scrounging, here’s a casting number and ID cheat sheet:

8.25″: 2852905, 3723598, 3723599. 10 bolt cover, round, but with “flattened”top and bottom

9.25″: 3507890, 3507891, 3723199. 12 bolt cover, octagonal shape.

Another sure genuine-Mopar axle ID tipoff: A rubber (snap-in) fill plug.This began in 1977.

Rick

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