amgis_obrut wrote:BW 78 series diffs with a 2.77 ratio will not accept or interchange with any other 78 series due to the offset on the crown any housing available with any other ratio will interchange
The BW found under a sigma is not a 78 series it is in fact a68 series has an 8 bolt hat and is much smaller than a 78
68 v 78
Wow, that's a big difference
.
From what I can determine, BW made two series of diffs from the early 60s - the 60/68 for small cars and the 70/75/78 for big cars. The Timken catalogue seems to tie in with that, with one wheel bearing code for most 4-cylinder applications and another wheel bearing code for most 6-cylinder codes. They list the small bearing for the Galant and the large bearing for the Sigma. Whether the bearing relates to the axle diameter, or the model of diff is unclear.
At least Ford bolted a useful tag onto their axles
e.g. "P/N 78DA-4005-MA Ratio 2.77 Ser No 5013". Is there one on the Sigma diff?
Mind you, even Spicer Axle (aka Borg Warner) sound confused, as their website states "In 1963, the company unveiled two generic rear axle assemblies, the Model 70 and 78, which, with modifications, would suit a wide range of Australian made cars." But small cars like the Datsun 1200 and Leyland Marina had the
model 60 or 68. Only the 78 seems to have had the LSD option, in either 25 spline 2-pinion (most 6s) or 28-spline 4-pinion (most V8s). Only 28-spline from about 1989 (EA Falcon and VN Commodore).
Measuring off the pics on the Datsun 1200 site, the 1200 model 60 looks to be about 6", and 120Y model 68 would be about 6.8", but the Skyline model 78 would measure about 8.5"
. Plenty of other websites claim the BW number is the crownwheel diameter in inches, so the photos must just be deceptive.
This is what I had read elsewhere :-
