Diff housing sizes

[L84THSKY]

I've asked alot of questions about diffs, but some things still seemed unanswered. We all agree that the 4 cylinder diff cases are smaller than the 6 cylinder cases. The stubs are different between 4 and 6 cylinders to keep the total width flange to flange the same size. Assuming this is true, then any 6 cylinder diff with the right bolt patter will fit our cars. The only issue would be getting the proper half shafts to go with the diff. That opens up the possibility of many 3/5/7 series cars to choose from.

My ratio of choice is 3.46 or 3.64. I have seen both those ratios offered in 7 series models. Here is a picture of a 3.46 out of a 1985 735i. Looks just fine for our applications. How many different half shafts are out there? Are there only 4cylinder, 6 cylinder and maybe M series half shafts?

[cali-ti]

diff cover looks different. will a stock e30 6-cyl, ti or m-coupe finned cover fit that diff? if not, how are you going to bolt it up to the diff cover mount on the ti?

after looking at all this stuff, i think your best/cheapest option is the club sport 3.45 LSD. find one, but it, install it, be done.

[L84THSKY]

That would be the simple solution, if I never planned to add a DASC or any other power upgrade.

But, the 6 cylinder housing seems to be beefier, and more suitable to any upgrades. If I do the diff right, from the start, then any proceeding upgrades won't require replacment of the diff again.

Originally Posted by cali-ti

diff cover looks different. will a stock e30 6-cyl, ti or m-coupe finned cover fit that diff? if not, how are you going to bolt it up to the diff cover mount on the ti?

after looking at all this stuff, i think your best/cheapest option is the club sport 3.45 LSD. find one, but it, install it, be done.

[m44ic]

Originally Posted by L84THSKY

That would be the simple solution, if I never planned to add a DASC or any other power upgrade.

But, the 6 cylinder housing seems to be beefier, and more suitable to any upgrades. If I do the diff right, from the start, then any proceeding upgrades won't require replacment of the diff again.

hey any luck finding a 3.64 diff that will fit yet?

[L84THSKY]

I have found both 3.64 and 3.46 6 cylinder diffs that will fit. Unfortunately, I didn't win them on Ebay.

Here is one I didn't win. Change the rear cover and the flanges and you are all set. This is a 3.46 LSD from a 735i.

Originally Posted by m44ic

hey any luck finding a 3.64 diff that will fit yet?

[cali-ti]

Originally Posted by L84THSKY

That would be the simple solution, if I never planned to add a DASC or any other power upgrade.

But, the 6 cylinder housing seems to be beefier, and more suitable to any upgrades. If I do the diff right, from the start, then any proceeding upgrades won't require replacment of the diff again.

the reason i had suggest the clubsport 3.45LSD was because the way you were talking before, you weren't going to DASC or engine swap in the future i guess someone is getting the buggaboo for more ponies now, eh?

so ... WHEN you do the swap, i HIGHLY RECOMMEND using bmw reman'd halfshafts. my shop said he's almost NEVER seen a bmw diff fail, but as i've found the halfshafts are a potentially different story. from crevier bmw in CA, reman'd e30 halfshafts are $260/each and i'll probably get a pair in the future to swap out these used ones (which still have some play so you get a little occasional clunk on shifts, most noticeable on 1->2 and 2->3 under power). my guy said he wouldn't recommend reman'd halfshafts either, then i said, "even bmw ones?" to which he responded, "yeah, shouldn't be any problem there." i think reman'd ones from bavarian auto recycling were like $350 so why the hell would i go anywhere else but bmw when i can get them for $260/each? also, getting them reman'd from bmw, you should get a matched set unlike what i have now. you also won't have to worry about which side they were installed on the car they were pulled from. you ideally want them to stay on the same side as what they originally were when going used, but of course you have NO IDEA what side they were removed from when sourcing them used (unless you get to take them off or can get the place to make note of that for you). see all the stuff i'm learning for you L8!? lol

[L84THSKY]

Hey Eric

You sure have been listening to what I've been saying. I did say I wasn't interested in a DASC or 6 cylinder motor. But on second thought, it seems smarter to just upgrade the diff to the large housing 3.46 or 3.64 LSD. That way I lose nothing in regards to any other future mods.

Turns out, finding a 3.45 LSD from a Club Sport is just as hard as finding a 6 cylinder 3.46 or 3.64 from any E30 style car.

So I might as well be a "Hldout" and find the diff of choice. My real motivation should be to finish work on the Vader seats.

[cali-ti]

i tend to agree with your new view of things, that's one reason i went with the 3.73 LSD from the e30. i just wish i'd known some things i've figured out along the way to make it easier and quicker so that i didn't have all this damn down time i really couldn't afford (much like you since these are our daily drivers). can't stress the bmw reman'd halfshafts enough, especially for "doing the job right the first time" and for longevity. that does increase the cost a bit ($260/each vs like $74/each used), but i think the peace of mind and (theoretically) not having to worry about them being matched and working right is certainly worth it. i WISH i'd done that ... can't go back now, but i can sure encourage others to do it that way.

[SportAuto]

I'm working with this dilemma right now- the M Roadser diff bolts right in, but puts the pinion flange approx. 1/2" forward of the stock location. The stock driveshaft has the proper bolt spacing however, and will bolt up, but in my case it must be shortened because the M3 engine also puts the trans back 1/2". The flanges on the M diff are 4.5", with a 94mm bolt spacing, whereas the 318ti flanges are around 4, with an 80mm bolt spacing. The splines are the same, but the 318 flanges will barely engage the internal diff splines so I'd rather not rely on them to transmit M3 power to the wheels. The ETK and my vendors show that there were two different axles installed in E36 M3s, both of which have a 4.5" flange. The smallest of the two has a 27mm diameter, which matches those in the Ti, so theoretically I'll be able to use the inner CVs from a 27mm/4.5 flange M3 axle on a 27mm Ti axle. I was shipped the wrong axles today (they sent the 38s) so I won't be able to confirm until Tuesday, but that's the idea. Using the M roadster rear subframe/trailing arms would probably alleviate this problem, but there are plenty of us looking to use 6 cylinder/M diffs in stock subframes so it'll be good to know. E30 flanges are the smaller 80mm spacing, with a 27mm axle -at least the 318 I measured for reference this morning was, don't know about the 6's offhand. I also measured an E34 525i this morning just for fun, and those are smaller as well. 540 maybe? I'll let ya know what I find when I have the new axles in my hands next week.

Tucker
SLO,CA

[cali-ti]

ugh ... so either way (using the m coupe diff or not), you have to mod the driveshaft? sux

the e36 (non-ti) halfshafts i know nothing about. i KNOW the e30 halfshafts will work and fit w/o change into the ti hubs/trailing arms. i'd bet you could swap the e30 diff flanges into the m coupe diff w/o change since the opposite (swapping m coupe diff flanges into e30 diff) works. the advantage of m coupe subframe/trailing arms/brakes is that they're all improvements over stock ti. you'll need to reconfig the parking brakes and possible routing of other brake lines/sensors. when i swapped in the e30 halfshafts, i needed to shim the ABS sensors, but that was simple enough because i knew about it ahead of time. i used 6-cyl e30 diff/flanges/halfshafts so i'm not sure if they 318 are smaller, the ETK would confirm or deny those differences i would think. as i stated before, i would hate to see you cobble together halfshafts with different CVs and such because it would be a pain in the ass later when/if you need to swap one. from my perspective, it's much more preferable to use stock parts, even if they're from a different model rather than cobbling something together to make it work. i beg you, don't do it man! lol

[SportAuto]

I'd rather not cobble it together, but it's all factory parts with fresh syn grease so I'm really not worried about reliability- the M subframe & arms just aren't in the cards right now. I don't think E30 flanges will work properly in the M diff for the same reason I'm hesitant to use the stock 318ti flanges, which fit too- they're just too short. I don't trust 250hp/tq and 1/4 inch of spline engagement

Tucker
SLO,CA

[cali-ti]

the 6-cyl e30 diff flanges are much longer than the stock 318ti flanges. i can take pics on tuesday when i get back in town if you want to see a visual difference between the two. i know constant also had a pic of those in his notes on the swap to e30 diff, let me find that (one moment) ... http://www.318ti.org/notebook/diff_c...ion/index.html

scroll down about 2/3 of the way to the bottom and you'll get a shot of the comparison between 318ti and e30 (6-cyl) diff flanges.

i certainly agree with you, i wouldn't even trust my 4-cyl with the short spline length in the e30 diff.

[L84THSKY]

Well, I won the diff I was looking for on Ebay, and at a very good price. The shipping was only $32.13, so the whole deal was under $200.00, can't beat that!!!!

No hurries about installing, I want to clean it up nice, and get the rebuilt half shafts too.

http://cgi.ebay.com/ebaymotors/ws/eB...RK%3AMEWA%3AIT

[m44ic]

Originally Posted by L84THSKY

Well, I won the diff I was looking for on Ebay, and at a very good price. The shipping was only $32.13, so the whole deal was under $200.00, can't beat that!!!!

No hurries about installing, I want to clean it up nice, and get the rebuilt half shafts too.

http://cgi.ebay.com/ebaymotors/ws/eB...RK%3AMEWA%3AIT

awesome let me know how it feels, I have been looking for a 3.64.

[cali-ti]

L8, can't tell from the pics ... is that a small or large case diff? see that it comes from a e30 318 so i'm thinking it could be a small case (not sure what they used in those).