[hassmaschine]

no.. the DSC controls the speedometer, and that's read from individual wheels, not the diff. There hasn't been a BMW that needed the cluster coded for a diff change since they stopped using cable driven speedometers (which I don't know that they ever have).

The DME does use the diff ratio to figure out what gear you're in but the effects of that should be pretty minor.

but why a diff swap and no performance tune? they really go together..

[Jashley73]

Originally Posted by hassmaschine

but why a diff swap and no performance tune? they really go together..

$$$$$$$ Although every diff-swap I've looked into is several times the expense of a tune. Man, I really bought the wrong car when it comes to the cost of mods...

Interesting to know that it calculates MPH from the ABS system... (Presumably)

O/T - I guess you're a machinist, that runs Haas CNC machines?

[Benan]

Originally Posted by Volasko

I finally got my car back on the road after my winter rear suspension rebuild. I just gotta say how happy I am with the new final drive ratio. I haven't had enough time on the road to properly comment about the fuel economy, but the new found acceleration is making me fall in love with the car all over again. This really is the final drive ratio BMW should have put in the car to begin with. I am super happy with this mod and recommend it to anyone with a 330i.

Sounds good

Is this a DIY project, did it take long?
What is the stock gearing on MT 330i?

Edit: Is this the diff you used?

[hassmaschine]

Originally Posted by Jashley73

$$$$$$$ Although every diff-swap I've looked into is several times the expense of a tune. Man, I really bought the wrong car when it comes to the cost of mods...

Interesting to know that it calculates MPH from the ABS system... (Presumably)

O/T - I guess you're a machinist, that runs Haas CNC machines?

I would only do a diff swap if I was also doing an LSD at the same time.. otherwise, I'd do a tune first. I would pick an LSD over a tune though!

I was thinking of the shorter gearing, then I realized some of the corners I like to take, I'd have to shift in the middle of the turn - with the stock gearing, I can wind out 2nd and shift when I'm going straight. it would only work (for me) if the gearing was substantially shorter (maybe 3.91 or 4.10) so I could be in 3rd gear instead of 2nd, but then that would be no good for the street.

heh, no - although I did work in a CNC shop (and on a Haas 4 axis mill) like 20 years ago. it's an "auf deutch" play on 1989's PHM...

[mbanks21]

Stock gearing is 3.15. I did a 3.64 from the auto at the same time I did the AA Software tune. I don't see why you couldn't just do the diff upgrade by itself though.

[Volasko]

Originally Posted by Jashley73

$$$$$$$ Although every diff-swap I've looked into is several times the expense of a tune. Man, I really bought the wrong car when it comes to the cost of mods...

Interesting to know that it calculates MPH from the ABS system... (Presumably)

O/T - I guess you're a machinist, that runs Haas CNC machines?

The car reads the speed of the rear half shaft from the bearing not the differential. The total cost for the diff swap for me was about $300 ($270 for wreckers yard diff with 80k miles + $30 for new fluid) as I DIY'd the install. It really isn't that hard to do if your confident with wrenches:

Chalk up front wheels, jack the rear end from the diff and put the car on jack stands under the rear lifting points. Remove the exhaust, it was easier for me as I already had the PE with pipe clamps which made the job easier. If you have the OEM exhaust it may be more difficult. Removing the drive shaft and half shafts are self explanatory. Dropping the diff is just a matter of having the jack under after you unbolt it and having a buddy help you lower it out. Total time should be about 4-5 hours if you take your time.

[Volasko]

Originally Posted by Benan

Sounds good

Is this a DIY project, did it take long?
What is the stock gearing on MT 330i?

Edit: Is this the diff you used?

Yeah it looks right.

[Volasko]

Originally Posted by hassmaschine

I would only do a diff swap if I was also doing an LSD at the same time.. otherwise, I'd do a tune first. I would pick an LSD over a tune though!

I was thinking of the shorter gearing, then I realized some of the corners I like to take, I'd have to shift in the middle of the turn - with the stock gearing, I can wind out 2nd and shift when I'm going straight. it would only work (for me) if the gearing was substantially shorter (maybe 3.91 or 4.10) so I could be in 3rd gear instead of 2nd, but then that would be no good for the street.

heh, no - although I did work in a CNC shop (and on a Haas 4 axis mill) like 20 years ago. it's an "auf deutch" play on 1989's PHM...

Doing a LSD swap takes this potential project from sub $500 depending if you DIY the swap to easily +$2000 if you rebuild the diff. For a daily driver that is over kill. This mod is easily up there with the PE and AA tune for extra driver enjoyment. The pull now in 2nd and 3rd is amazing.

[hassmaschine]

I believe it. It's just that for where I drive, it would actually make the corners slower, because shifting 1/2 of the way through a corner at speed isn't a good idea. so I'd either have to shift up earlier (and be out of the power band), or ride the rev limiter until I exit the corner.

[StealYourFace]

Shorter gearing does indeed wake these cars up, makes them feel a bit lighter on their feet. I had 3.64s for a bit but when that rear end broke, I did 3.38s, which turned out to be a nice happy medium.

[ff54976]

stealyourface:

what were your rpms at 70 or 80 with 3.38, 3.64

[Jashley73]

I'm with Haas on this one. No point in me doing a diff swap if I can't also do an LSD to help keep the power down, especially Iin the corners... My other car is an E30 with an AWESOME 3.73 LSD and there is no comparing how the two cars put down the power. But like Volasko said, putting a LSD into a diff, makes the swap 3-4x more expensive. I started researching putting an M3 diff in the car, but I'm not sure how much a used diff would be, and it seems like you have to chop-up, or at least piece-together a driveshaft. There doesn't seem to be an inexpensive way to do a diff+LSD swap right now...

If I found a solution, I'd probably DIY this, at the same time I did a muffler...

[Benan]

Thanx for the info! This got me to order a 3,64 lump

[MFactory]

No need for expensive M3 Diff conversions, when there are plenty of LSD choices on the market.

[Volasko]

Incase anyone wants to see an acceleration video, I think I'm the first to do this!

Edit: This video was taken when my main large DISA valve had failed which doesn't show up in the codes. This wouldn't be accurate.

[stewey]

Thanks for the video! Has your 0-60 time improved?

[StealYourFace]

Originally Posted by ff54976

stealyourface:

what were your rpms at 70 or 80 with 3.38, 3.64

at 75 2700 with 3.38 and 3000 with 3.64

[Volasko]

Originally Posted by stewey

Thanks for the video! Has your 0-60 time improved?

It's hard to say, I never really trust those phone 0-60 apps and I don't have any fancy GPS data loggers. There is another 2-3 shift needed now to reach 60 due to the different final drive ratio, so I would say its a wash.

[stewey]

Thanks for the follow up. I should have asked about acceleration in general. What's your take on that?

[Volasko]

Originally Posted by stewey

Thanks for the follow up. I should have asked about acceleration in general. What's your take on that?

It is noticeably improved, every gear feels stronger due to the new final drive ratio. It is to be expected as there is 15% more torque being applied to the wheels. My average economy has gone down which is to be expected but not as much as I thought. I used to average about 625km/tank, now I'm lucky if I reach 600km. Not a huge change but a change none the less.

[stewey]

Nice thanks!

[Jashley73]

My question though - with the extra torque, how does it put the power down, especially in corners? More slip/DSC action now?

I'm still considering this, but I really don't want to sacrifice the highway cruising, and I'm concerned about cornering with the extra torque and no LSD. There's just no way I can justify $2000 for a new LSD/ratio...