LSD upgrade

[kord83]

My friend has 318ti with 3.46 open diff he wants to upgrade to LSD whats the must common upgrade he tried 3.91 LSD and don't like the high rev on the highway. Any recommendations ??

[cooljess76]

Any recommendations ??
Yeah, try searching.

I mean common sense would tell you that if a 3.45 revs at 3800rpm @ 80mph, a 3.91 would be significantly higher. If he wants to lower rpm's, try running a 3.25 out of an e24 or stick with a 3.46 out of an e28 to keep it around the same rpm.

[kord83]

I know is common sense .... I was just wondering if anybody tried any other variations . like 3.73 if there is LSD with that gear . He likes the acceleration but don`t like the high rpm. I know he cant have both. Just something in between.

[cooljess76]

Oh I see, well you can always look up a final drive/rpm calculator.

Edit, here try this:
http://368s.com/tools/rpm

Just enter your final drive ratio and tire size

[kord83]

Thank you ! That is perfect !

[mohaughn]

Yes, there is a 3.73. Get the mid size diff case, holds more gear oil, and you can also run the super cool m-coupe finned diff cover.

[cooljess76]

So far every single M Coupe finned cover I've seen has been chipped or damaged from hanging so low. I don't see what the big deal is about them personally and if your car is lowered, I'd definitely advise against one. I'm sure they cool a little more effectively, but at the risk of getting cracked, draining all of the fluid and leaving you stranded somewhere with a blown rear end.

+1 on the medium case diff though. They're much stronger than the small cased diffs our cars came with. FWIW, 4cyl BMW's got small case diffs from the factory, while 6cyl cars got medium cases. Regular e36 diffs won't fit the 318ti because the mounting is completely different. Instead, you'll need either a Z3, M Coupe, or e30 diff. E24 and e28 diffs will also work, but you'll need to swap the cover and output flanges from a Z3, M Coupe or e30.

I know a few members here have forced their stock 318ti halfshafts onto medium case diffs. I strongly urge you not to do this as the 318ti halfshafts are too long and have weaker cv joints. E30 halfshafts fit perfectly with medium case diffs and are significantly beefier. The halfshafts need room to pivot and by cramming 318ti halfshafts onto the wider- medium case diff, you're restricting it's range of movement, thus putting excessive strain on the cv joints. I suggest purchasing a set of e30 halfshafts from a 6cyl model with ABS. The 4cyl models will have longer halfshafts since they use small case diffs, which is what you don't want. You can tell if the halfshaft came off of a vehicle equipped with ABS by looking at the outer cv joint. It should have a gear-like toothed ring. This is called an ABS tone ring. You'll notice that the tone ring on the e30 halfshaft is somewhat larger in diameter than the one on the 318ti halfshaft. This means that you'll need to shim your original ABS sensor(s) to clear the larger ring. A simple washer with a 5/8" opening works well. And finally, the speed sensor. It's located on the differential cover. It needs to be the same length as the one that came with the diff you're installing. It works exactly the same way the ABS sensors do. The Ti speed sensor is too short for medium case diffs. So if you use a e28 diff with an e30 cover, the e28 sensor has a different style connector than the Ti. Try to find an e30, Z3 or M Coupe diff cover with the same style connector. Then remove the speed sensor and hold it next to the e28 sensor and verify that it's the same length.

I know it's a lot of info to remember, but if you do things right the first time, you won't have any problems. Hope this helps.

[cooljess76]

http://www.318ti.org/forum/showthread.php?t=21516&page=5

[pnosker]

If you're planning on autocrossing, I swapped a 2.93 LSD in from an E30 eta model and that lowered my points from C class to E class where I'm very competitive again (wasn't in C). So keep that in mind for your car if you're planning on racking up points in mods.

[FMD]

how did that work?

[1996 328ti]

So far every single M Coupe finned cover I've seen has been chipped or damaged from hanging so low.I have a fin cracked from my mechanic dropping it. :(

[pnosker]

how did that work?

Class is based off the Boston CCA points system. The multiplier for diff is (New diff/Old Diff)*(Points) so mine are lowered to slightly below the upper threshold for E class. 2.93/3.46 = 84.68% of total points = new points.

[cooljess76]

how did that work?

on an autocross course, people generally never reach speeds above 50mph. So someone with a swapped or FI car would have a significantly unfair advantage by running a 4.44 or high ratio diff since top speed is not a factor and acceleration would be off the hook. I can see where they have to draw the line and set up some sort of rules to regulate some of the ridiculous mods people do to win an event.

[kord83]

:) Autocross is different story. My friend is using the ti for everyday driver. I have e30 325e ( was auto now sick) with top of 325i (head, intake, injectors, harness, ecu .. ) i just installed 4.10 LSD and i`m very happy with it perfect for my next autocross season. Thank you all for the help and info . Specially that think was helpful for him do decide what he will be comfortable with. --->

Oh I see, well you can always look up a final drive/rpm calculator.

Edit, here try this:
http://368s.com/tools/rpm

Just enter your final drive ratio and tire size

[cooljess76]

:) Autocross is different story. My friend is using the ti for everyday driver. I have e30 325e ( was auto now sick) with top of 325i (head, intake, injectors, harness, ecu .. ) i just installed 4.10 LSD and i`m very happy with it perfect for my next autocross season. Thank you all for the help and info . Specially that link was helpful for him do decide what he will be comfortable with. --->

No problem man. Ahhh, a 325 stroker you sly devil you:biggrin: I've had a couple friends who did what you did to their e's, nice upgrade. Total sleeper:wink: Honestly, I think it's the best bang for the buck if you have the resources. Especially since it can literally be done with parts you have laying around the garage, lol. Tell me you left the badge on the trunk.

[kord83]

And the rust all around :)