Does anyone know what the o/d of the diff flange on a 7" sierra diff, also the PCD of the 4 bolts and the o/d of the ring in the middle of the flange?
IIRC the o/d of the flange is 100mm (i think)

Tommy

do you mean the input or the output flange (I guess input as your say 4 bolts)

~100mm is the O/D of the CV joints / output flanges

I have swapped from a 7 1/2 diff to a 7 inch and the flanges are the same

if that helps.

the 4 bolts are not equall spaced,
~60x67mm rectangle.

i need to get a speedo ring made up to go between the prop shaft and diff, i can get it made up for free but i just need the dims

with my cheap digital caliper-
outside diameter 109.45mm
inside shoulder diameter 55.94mm
four holes 10.45mm diameter with centers on a 59.93mm x 66.91mm rectangle.