Originally posted by KLANDERMAN
http://www.rcmart.com/catalog/produc...oducts_id=7253
If the above link doesn't work, try this...
The home page is www.rcmart.com , go to parts, select Gp, then pick the HPI r-40 and select the brand three racing, they have many optional parts here... the rear casing is on the second page... good luck!
An aluminum dif case and gear will probably add quite a bit of rotating mass. The picture also doesn't show the internal side so I'm not sure if it will accept the 4 gear conversion. Reducing rotating mass is half of the purpose of the .8 pitch 2 speed, so adding weight to the rear diff probably wouldn't be your best choice. Are you having problems with the stock case and gear?