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1. The upper bolting strip of the differential housing (DH) sat in a recess cut into the glacis, so its relative position to the glacis surface could vary with tolerances on machining, casting, and part thicknesses.
2. The recess bottom was not parallel to the glacis but tipped out at a 2 degree, 37 minute, 33 second angle such that it was deeper at the bottom of the glacis than the upper part. It was nominally 7/8 inch deep at the bottom on 2 inch thick glacis plates. The notch for the DH was 2-1/2 inches wide from the edge of the glacis that sat above the fenders, and the recess for the DH bolt flange was 3-1/8 wide. The bolt hole centers were 1-3/4 inches in from the DH notch, so they were not centered in the recess. (Ref. C97184, PLATE, LEFT FRONT)
3. The height of the lower hull plates varied on tank type and factory because the edges of the plates were shaped differently to suit different welding techniques. I believe the assembled hull dimensions would be the same though. For the M4A2, the distance from the bottom of the sponson to the bottom of the side hull plate (not necessarily the bottom of the hull but maybe close enough in 1/35!) was 28-13/16 inches. (Ref. E3790, HULL ASSEMBLY)
4. As to the bolt flanges on the DH, the dimensioning was rather convoluted. The important features to be controlled were all located relative to the gear shafting of the final drive housings (FDH), not the bolting flanges. So, here goes . . . First draw intersecting horizontal and vertical lines. From the intersection (called O), draw a line to the upper right that is 36 degrees down from vertical (called OV) and a second line to the upper left that is 36 degrees above horizontal (called OH). OV should be perpendicular to OH. Now draw a horizontal line (called H1) 14.204 inches below O, and a vertical line (called V1) 14.750 inches to the left of O. Draw a line parallel to OV (called OVa) 10.311 inches to the left; and a line parallel to OH (called OHb) 13.878 inches above. H1 should intersect V1 and OVa should intersect OHb. Now, here's what that means: O is the center of the input shaft (the center of the radius making up the small end of the FDH in my sketch). The H1 line is the inside surface of the bottom DH bolting flange; V1 is the centerline of the bolts in that flange. The OHb line is the inside surface of the top DH bolting flange; OHa is the centerline of the bolts in that flange. (Note that the DH sits below the hull floor plate and above the glacis plate.) (Ref. E8543, HOUSING ASSEMBLY, DIFFERENTIAL)
The drawing thoughtfully provides a checking dimension directly between the center of the top and bottom bolt holes on the inside of the two flanges: 34.6976 inches. This is a direct measurement between the H1-V1 and OVa-OHb intersection points.