Discussion
As you may gather from my previous post regarding the e90 325/330i differences, I'm slightly underwhelmed with the car on the excitement front, (not suggesting its a bad car in any way shape or form), I'm just used to and like more livelier cars, it makes financial sense that I keep it and very convenient too, so lumbered with it really, already got eyes on a ported throttle body for it and decent air filter then maybe get it remapped, realising its not going to break any records, but may give me a tad more pleasure. Any way, before I decided to keep it I was looking at an e46 330i with 75k on the clock, a bargain really for 2k and what was appealing about it was it had a 3.38 diff in it, no idea what that is or means but looking on ebay it seems they come from smaller engine e46's and he reckoned in his ad that it made all the difference with the low end pick up and made it much more sharper at low revs, So, is there an equivalent diff that would work in my e90 330i?
Having tried a non standard “shorter” diff in an E46 I wouldn’t recommend it. When I converted my 330d to a manual I briefly had an auto diff with the manual box.
If you want to be a drift king (or drift queen) or just drive like a loon round town racing away from the lights it would be great. It does give faster acceleration at low speed. On open country roads you could almost drive everywhere in 5th. However you had to change straight out of 1st as you pulled away. Anything past 70mph had the engine revving too high for peaceful driving. I imagine mpg would be worse too. But as with all choices in life we all like different things. This is my experience and based on that I wouldn’t go for a shorter diff for an all round daily driver BMW.
If you want to be a drift king (or drift queen) or just drive like a loon round town racing away from the lights it would be great. It does give faster acceleration at low speed. On open country roads you could almost drive everywhere in 5th. However you had to change straight out of 1st as you pulled away. Anything past 70mph had the engine revving too high for peaceful driving. I imagine mpg would be worse too. But as with all choices in life we all like different things. This is my experience and based on that I wouldn’t go for a shorter diff for an all round daily driver BMW.
E46 325i auto is 3.46
E46 330i auto is 3.38
E85 Z4 manual 6 speed is 3.07
E46 330i manual is 2.93
That’s 4 that I know off the top of my head. The above are all in a 188k (medium) diff casing.
M3 comes with 210mm casing and needs different diff carrier to work, the 4 cylinders 316/318 etc come with 168mm casing.
E46 330i auto is 3.38
E85 Z4 manual 6 speed is 3.07
E46 330i manual is 2.93
That’s 4 that I know off the top of my head. The above are all in a 188k (medium) diff casing.
M3 comes with 210mm casing and needs different diff carrier to work, the 4 cylinders 316/318 etc come with 168mm casing.
Edited by Mgd_uk on Sunday 1st October 08:06
ZX10R NIN said:
Why not fit a Quaife diff to your car it does make for a better drive when pressing on.
Indeed.Depending on how good you are with spanners swapping another BMW open diff with an alternative ratio is somewhat easier than cracking the existing diff apart to install an aftermarket LSD. That said you are absolutely spot on when you say a Quaiffe LSD is a much better option.
OP: in case you are unaware Quaiffe are a manufacture of limited slip diffs, there are also kits available from KAZZ, Peloquin, Wavetrac, Torsion & MFactory to name a few.
There are different types of LSD as well, some are more suited to road use and don't require rebuilds, some plated types can be rather aggressive & have a service life.
sounds like it could be expensive, if I just wondering if I could grab one off ebay for 50 quid that belongs on a different car and as my mechanics rates are quite cheap let him swap it, if they are too harsh then i'll leave it, I was just curious, great help though guys. I'm not interested in spending a fortune on the car, if I had loads of spare money, id sell it and just get another s4, I was looking at cheaper options just to make it a bit more interesting really
Mgd_uk said:
Quaife won’t change the ratios tho, giving him little acceleration benefit from changing to a higher final drive ratio.
True on the open road a LSD won't make the car feel like it has more power/rev quicker in the same way as shorter gears/higher final drive, but acceleration is improved by being able to put the available power to the tarmac more effectively. 
Welded diffs are great for sudden loss of traction in the wet as well as breaking driveshafts and working the securing bolts loose.
The 330i manual has a 3.15 ratio diff, 188 casing three bolt prop flange. The Auto has a 3.64, a direct swap. It'll certainly pull a lot better in 4/5/6 but first gear would be quite low. The 330i has a unique diff; like the diesels it has a three bolt prop flange and a guibo (rubber coupling) at the diff end of the prop, the 325i has a similar diff but with a metal four bolt flange and the four cylinder petrol toss all use the 168 diff of doom that shags itself for fun. The 330i diff has a limited market used, and rarely wears out meaning they're almost worthless - I've seen these sell for 200 quid on Ebay. For £200 and two hours of swearing under the back of the car, a 3.64 is worth as pop. It might do just what you want.
Here's a 3.64:
http://www.ebay.co.uk/itm/BMW-E81-E87-130-E90-E91-...
The 330i manual has a 3.15 ratio diff, 188 casing three bolt prop flange. The Auto has a 3.64, a direct swap. It'll certainly pull a lot better in 4/5/6 but first gear would be quite low. The 330i has a unique diff; like the diesels it has a three bolt prop flange and a guibo (rubber coupling) at the diff end of the prop, the 325i has a similar diff but with a metal four bolt flange and the four cylinder petrol toss all use the 168 diff of doom that shags itself for fun. The 330i diff has a limited market used, and rarely wears out meaning they're almost worthless - I've seen these sell for 200 quid on Ebay. For £200 and two hours of swearing under the back of the car, a 3.64 is worth as pop. It might do just what you want.
Here's a 3.64:
http://www.ebay.co.uk/itm/BMW-E81-E87-130-E90-E91-...
Edited by iSore on Sunday 1st October 18:52
iSore said:
£150!
that would be a bit more like it as technically they are worthless as you say, obviously I'd need to see what my mechanic would charge, partly so I could swap it back if it was too expensive. I understand and taken on board peoples opinions regarding this and it does seem very appealing provided it isn't too extreme so I need to think about it but now I have the option and know what I needGassing Station | BMW General | Top of Page | What's New | My Stuff