Some info to share. Didn't want you guys to be ignorant of the Fox variant Diffs we used in the Antipodean and European Group A Mustangs
I found out all this while I was doing some research on generic Sterling 6.7/6.875" 8 bolt US diffs.
(3.45/3.08/2.73 ratio light duty Ranger/Fox/Pinto/Mustang II 8 bolt diffs, 23 spline after 1974, other ratios were 3.40, 3.18 and perhaps a 3.55, all non locker diffs sadly.), I found another Factory endorsed Motorsport source for a better light but stronger Fox diffs.
Internally the Sterling 6.7/6.76/6.875 lookes to be very similar to our 10 bolt European/German Atlas diff used on factory and Works Ford Capris and BDA Escorts, IRS Granada Mk 1,2,and 3 (Cologne engined European). See
http://www.classicfordmag.co.uk/file...definitive.pdf
http://www.fordopedia.org/varia/rear...wheel-bearings
http://www.robs7.net78.net/
What is the ZF Atlas? To Americans, it's the diff used on the 2.0, 2.3, 2.6 and 2.8 Euro Mercury Capri imports from 1971 to 1978. In your US market import cars, they were normally 3.22, 3.45 and 3.75, but there were also live axle 3.09, 3.44, 3.50, 3.70, 3.89 ratios in RS 2600, RS 3100, 2.8, 2.8i and 2.8 Turbo version made from 1979 to 1987 in the overseas German and British market versions. It first came out in GT German Escorts with the E code diff, and about the same time in Capris and Transit vans. Much later, the similar 4.6 and 5.1 ratio stump puller gears came out in 80's Transits and P100 pickup trucks
It was also the all conquering World Rally wining RS 1800/2000 Diff in the 1979 Works Escorts.
Ford of Europe did lots of pivotal development work, and farmed out the axle supply for various models to Zahnradfabrik, (ZF Gear) in 1969 for some versions of the German Escort, the EscortTaunus TC and 1970 Mk I IRS Granada (3.15 and 3.61 ratio in these), and some 2 liter Mk 3 TC Cortinas from 1971 on to 1984 Mk5 TF versions. The result was a very light axle which is smaller than the Ford 8", the 7.25, the 7.5 and 8.8 and 9" diffs, but it puts its 7.5" crownwheel into a very compact housing. It used to be used with mild 302 Windsor and C4 gearbox variants on 1974 Granadas, thw worlds easiest 302 swap. Its the E type diff
Its not the best diff, it's no 9 incher, and Dick Johnston used to use the 9" Diff in his racing Mustangs instead. What it's got is parts supply ad infanatum, and real light weight, with full floater variants which won't loose wheels in a race, and standard 4 by 4.25" bolt spacing andusually, the standard Fox body width which results in a 56.6" track.
Over the last 44 years, competition European Ford diff tuners in England have reworked over 5000 units, since they are light and easy to work on. One out fit (
http://gartrac.com/shop/atlas-axle-p...l--pinion.html) can supply any other non std ratio from 4.1:1 for £477.93 tax excl
4.6:1 and 5.1:1 for £309.69 tax excl,
5.3:1 and 5.8:1 for £477.93 tax excl
Some centres were homologted for Group 2 /Group A use in the XR4TI Merkur and Sierra Cosworth.
The 10 bolt Atlas diff was also homologated as a race diff when the MacLaren Mustang came out, and the early Group 2 and Group A papers had it listed from when Ford Motorsport filed the papers to FISA in 1982. See this Atlas homologation diff in a New Zealand rebuild of Dick Johnston Greens Tough No 17 Mustang.
Race homolgations for the Group A Mustang with turbo 2.3 or 5.0 4bbl were 7.5" Atlas 3.44, 3.75, 3.89, 4.11
They have 3.09, 3.22, 3.44, 3.45, 3.50, 3.70, 3.75, 3.89, 4.60 and 5.1 ex factory, with some special 3.9, 4.1, 4.11, 4.44, 5.30 and 5.8 options specially made, but like most diffs, the crown wheel size varies from the 7.5" maximum...the case will carry to less than 6.75 inches in some ratios. Funny thing is, on some versions of the German Capri Atlas, the Volvo bits (brakes and outer timkin bearings, for example) from 1 and 2 series 164/264 Dana 30's bolt on to this diff.
See how its used in the New Zealand and Aussie Group A Mustangs!
See
http://www.rallyanarchy.com/phorum/r...?1,70674,70861
http://livethedreamgroupa.blogspot.co.nz/
Due to the problem with finding good Fox 7.5 and 8.8 diff housings at a competitive price down here, I was going to use the Borg Warner 9 Bolt GM F-car M78 Rearend or "78 series". 7.625/7.875" BTR diff found in Falcons, Valiants, Commodores, Camaros and Firebirds, Centuras and Aussie Cortinas, Pintaras and Skylines. They are basically a Salisbury diff, used internationally since GM's Holden subsidary was able to organise it for the F cars when the PBR braking system was also outsourced for F cars and 84 onwards Vettes. That Australian brake and axle content allows a Fox body owner to pick up Commodore VK to VP Panhard rod four link diffs and SVO style brake kits to be made using the US M78 F-body axle.
So I looked into it a bit more
http://i1215.photobucket.com/albums/...pscc5823ff.jpg
(A lot of very tricky US Fox body axle conversions are actually enginering precedents from early NASCAR and Works Rally Escort practice which GM copied on the V car, and in turn this technology has filtered into US Fox body practice via Australian Touring Car and AVESCO based systems. A lot like the Panther Watts linkage being a Works 1979 WRC Escort/Toyo Koyo RX-7/ Aussie 1982 to 2002 Falcon set up).
I found out that the picture I copied off Ken Hoppers Atlas diffed Group A Mustang
was a catalyst in getting more Atlas Mustang info from the net...
The Atlas is fairly common down here, my old V6 Cortina had it, all 3 liter Capris, and a few station wagon Cortinas too. Lots of Works and Ford Motorsport Escorts had the diff too. Not hard to get ratios or housings if your good friends with the old rallye Escort people. The Fox Mustang runs a Escort/Capri/Cortina stud pattern, and a 4.6 or 4.1:1 limited slipper ratios suit me just fine when the US AOD autos turn those into 3.08 or 2.75:1 over ratio tops, just great for highway cruising and drag race or circuit bruising.
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