What is the stock D-90 R&P size in inches?

Ring gear diameter is around 8.5 inches. But don't use this as a guide to comparisons with other differentials. Due to the obsolete spiral bevel construction and the tooth count the Rover type ring and pinion are among the weakest on the planet.
Bill.

What is exactly the difference between a standard hypoid set up and a spiral bi-level one, any diagrams to see?

What is exactly the difference between a standard hypoid set up and a spiral bi-level one, any diagrams to see?


i don't know about diagrams, but there are plenny of photos that have been taken of broken ring gears that illustrate the differences pretty clearly.

What is exactly the difference between a standard hypoid set up and a spiral bi-level one, any diagrams to see?
Google is a good thing!
Here you go, diagram here: http://www.tpub.com/content/engine/14081/css/14081_61.htm


"Types of Differential Gears
There are two designs of differential gears, hypoid and spiral.
Spiral Differential - In spiral differential the pinion gears contacts the ring gears at its centerline .
Hypoid Gear - In the hypoid the pinion gear contacts the ring gear below the centerline. The size of pinion gear in hypoid differential is much smaller and the contact ratio is high, comparatively hypoid differential is much stronger than the spiral differential. "
http://www.gears-manufacturers.com/differential-gears.html