Ahmedsinc 414 Report post Posted October 25, 2014 So I've been doing a bit of digging around on diffs and there's something I'd like to try. According to bimmerdiffs.com the pinion tooth count is the same between 3.15 & 3.46 - both use a 13 tooth pinion gear. Ring gear counts are different - 3.15 uses a 41 tooth, 3.46 has 45 teeth. I have a 45 tooth 188mm ring gear from an E39 3.46 in the shed, but I'd like to get my hands on a complete 3.15 to have a go at swapping the crown wheels. My original idea was to swap the ring & pinion to another E36 case but unfortunately the E39 uses a much shorter input shaft, so that's a no - go. So does anyone have a 3.15 medium case they'd be willing to donate or sell for a small fee? Overall condition is irrelevant as it's purely for research purposes, so if it's leaking oil everywhere or the bearings are stuffed thats perfect Yes I know it would be easier to swap in a 3.46 from a Jap 328i auto but there's no fun to be had in that, is there Thanks in advance Quote Share this post Link to post Share on other sites
yng_750 247 Report post Posted October 25, 2014 Tooth count isnt everything. Id say the pinions are different shapes and sizes Quote Share this post Link to post Share on other sites
Ahmedsinc 414 Report post Posted October 25, 2014 Yes, but it's a good start though. Might rip the centre out of the 3.73 and make some comparisons between the ring gear thickness and tooth height etc. Guess it's possible that they completely redesigned the diff internals when the E39 was released, but it would be handy if they didn't! Quote Share this post Link to post Share on other sites
allan 295 Report post Posted October 25, 2014 If interested have a 3.46 to 1 medium case diff out of a 325i traveled around 108,000k 1 Quote Share this post Link to post Share on other sites
Ahmedsinc 414 Report post Posted October 26, 2014 Well, so far so good. Figured out how to disassemble the E39 diff and retrieved the ring gear. Did the same to the E36 diff and eyeballing the two suggests they're identical. Ring thickness, tooth depth, bolt pattern, thread & depth all look the same. Will be borrowing a vernier caliper and hopefully a micrometer as well later on this week to take some proper measurements, also plan to give Mr Barrie a call and find out what he has to say too. Seems silly to buy a diff when I have the bits I need already, and the opportunity to learn more about the dark art of differentials is too good to pass up. Wish me luck! Quote Share this post Link to post Share on other sites
BM WORLD 1283 Report post Posted October 26, 2014 have 3.07 and 3.15 med diffs for sale . Quote Share this post Link to post Share on other sites
ashmill 68 Report post Posted October 26, 2014 Interested - please advise price. Quote Share this post Link to post Share on other sites
Michael. 2313 Report post Posted October 26, 2014 I have a a 3.15 ring gear and pinion for $50 Quote Share this post Link to post Share on other sites
Ahmedsinc 414 Report post Posted October 26, 2014 I have a a 3.15 ring gear and pinion for $50 Bummer it's not the complete diff. Pinion tooth count is identical on the .46 & .15 diffs, I need a complete unit to practice on before I go tearing my 3.15LS apart. Cheers for the offer though, if I can find the money in time I could definitely use your S50 midsection! Quote Share this post Link to post Share on other sites
jeffbebe 1559 Report post Posted October 27, 2014 I have a 3.15 open diff... But large case, so probably not much good to you. Quote Share this post Link to post Share on other sites
jeffbebe 1559 Report post Posted October 28, 2014 Swap meet? I'll exchange my 3.15 large LSD for a 3.64 equivalent if anyone is game. Go on. I probably will be keen when I put in a six speed! Quote Share this post Link to post Share on other sites
Ahmedsinc 414 Report post Posted October 28, 2014 I have a 3.15 open diff... But large case, so probably not much good to you. Unfortunately yes. Thanks for the thought though Surely someone has a ratty old med case 3.15 they could donate in the name of science and a little pocket money?? Quote Share this post Link to post Share on other sites