The Sierra Diff was quite hard to measure and draw up. I started with the push in shaft 7″ ‘Tripod’ version.
Most of the time drawing up this Ford Sierra Differential was taken during the measurement stages. When there are so many dimensions to be taken you almost need a 3D model to plot them on. It’s the whole ‘chicken and the egg’ situation.
To double check the dimensions I drilled some holes piece of MDF, then tested whether bolts passed through them lined up with the diff. Crude, but it did give me some piece of mind as everything seemed to line up just fine.
I have two 7″ differentials, a Tripod type and a Lobro type. It was interesting to note, that although the bolt / mounting points were identical there were a number of shape differences in the casting. Small lumps and bumps, nothing major but you could see that over it’s lifespan Ford like to tweak the design.