In reply to # 1473715 by Tote 3. Why 17 bolts to hold the bell housing onto the engine plate?!!!!!
One reason so many bolts is that the bell housing is aluminum, and a casting to boot. So it tends to be brittle and needs loads spread out over a larger area to avoid fractures and cracking. If the housing were cast iron or steel, then many fewer bolts could be used.
Two of the bolts secure the starter motor, which is not light in and of itself and gets a substantial torque applied to it during starting..
The motor/tranny combo is supported at the motor, and at the tail of the transmission. The motor wants to tip over backwards as the motor mounts are not in the center of gravity of the engine. This places a bending moment that is at its greatest where the transmission is mated to the motor. As already explained an aluminum casting is not the strongest choice, hence the number of fasteners.
Lastly I will mention that earlier bell housings (TR4s) had a thinner lip where it attached to the engine. Cracking and breakage occurred, so later castings were beefed up in this area. The TR6 uses the same gearbox as the TR4 but with the thicker casting so none of us have had that particular problem. I mention this simply to point out that design elements of the engine/gearbox attachment have evolved over time and addressed specific problems - some of which were driven by the fact that the bell housing is fragile compared to the engine plate to which it attaches.
1980 Platinum Metallic TR8, navy blue interior
Bare metal respray, Crower cam, raised compression
ported heads, modified Zenith carbs, 0.060" overbore