Cement 876 Report post Posted November 10 So I got my 3.91 ratio diff (https://bimmersport.co.nz/topic/69192-wtb-e46-mid-case-diff-or-ring-pinion-373-or-391/) and disassembled it, but the crown wheel looks to not actually measure 188mm as expected đIt measures more like 168mm which would mean it's actually a small case. Does anybody know if the 188k should actually measure 188mm where I am measuring as pictured ? Stamped code on the ring gear is HK2V PE1 951 0615 which I can't seem to link much back to. @HELLBM are you able to link this item back to the vehicle it came out of or offer any guidance here ?  Quote Share this post Link to post Share on other sites
Eagle 1662 Report post Posted November 10 I thought all 3.91 were small case? Yeah 188k measures 188mm in diameter Quote Share this post Link to post Share on other sites
Cement 876 Report post Posted November 10 Damn it !! That really blows ... chart here says the 3.91 was in the 2.5l N52 model. http://tomic.ba/fs/cjenik/E83 Technik 0307.pdf Quote Share this post Link to post Share on other sites
Eagle 1662 Report post Posted November 10 Maybe there is a small and medium then? There's a guy facebook trying to sell a X3 3.23 diff because it didnt fit his E46, turns out its a large case unlike the E46 one which is a medium in the same ratio. Quote Share this post Link to post Share on other sites
F10er 65 Report post Posted 17 hours ago A little late to the party here, so it's probably useless info but if you use realoem.com, it tells you what the ratio is and what type of diff it is. In this case it looks like the 3.91 comes in type 168 and 188. The 168k looks like it comes in cars with an automatic trans and the 188k is only used in manuals. Quote Share this post Link to post Share on other sites
F10er 65 Report post Posted 17 hours ago Another thing i learnt from my BMW diff nightmare was, a type 168k diff has 7 bolts holding the rear diff cover. A type 188k has 8. Quote Share this post Link to post Share on other sites
