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Discussion Starter · #1 ·
I've been told that my 2000 323ci 5 speed has a 3.07/1 final drive. Is it possible to throw a 2001 325i diff in with little work? Will I have to swap flages? Is the 325i a 3.15/1 or a 3.46/1? The diff in question is from an auto if that matters
 

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The 325i auto uses a 3.46 diff, as do all the e46 autos. Here are the others:

323i,Ci (man): 3.07:1
323i,328i,Ci (auto): 3.46:1
328i,Ci (man): 2.93:1
325i,Ci (man): 3.15:1
325Ci Convertible (man): 3.41:1
325xi (man): 3.23:1
325i, 330i, ci, xi (auto): 3.46:1
330i,ci (man): 2.93:1
330xi (man): 3.07:1

I've been thinking about switching diffs, too. Do you have any idea what kinds of prices to expect?


Dave
 

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Discussion Starter · #3 ·
First of all thanks for the reply. I'm a new user and I'd like to say I've learned so much from these postings. I'm not sure the correct amount to pay for this swap, but Dinan was more than happy to chage me 1500 + labor for the swap (would they keep my 3.07)?. Anyone, done the swap? How many rpm would I be turning with 19'z @ 85mph is the real question........
 

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I have a 328Ci mod 2000 steptronic with 3,07 differntial and have no problem.The max speed I have reached is 230km/hr at 6100 rpm and if Ipushed it harder perhaps I 'd reaced 240.
At 2000rpm the gauge shows 100km/hr.At 2800 rpm 150km/hr.
:) :) :)
 

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so badwayz, did you get the install? how is the performance? any "buzzing" at highway speeds? gas mileage decrease? performance increase?

i'm seriously considering this mod, but would like some first hand feedback...

thanks...
 

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Awesome.
Tell me how it is. I'm thinking of doing it at some point, and I'd love to hear what you think. :thumbup:
 

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Well
I've noticed increase in the acceleration.I can get now top speeds pretty faster,the increase in the consumpion is immaterial and there's no buzzing at all at high speeds.The 3,07 and 2,93 are officially recommended by BMW for the steptronics.If you go to a faster one such as 3,23 or 3,46 you will loose in consumtion and high speeds but perhaps you get even faster acceleration at low speeds and a change in the management might be necessary.
The choise is yours


:thumbup: :thumbup: :thumbup:
 

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Thanks a lot bro :thumbup:
I'm definitely thinking about it.
 

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Discussion Starter · #11 ·
Has anyone officially done this mod to a manual:
2.93:1 or a 3.07:1 to a 3.46:1 diff? I have a guy that's willing to sell it to me for 2bills. I can get it installed for another 2 bills. 3.07 to 3.46 is a big jump. Is it a direct swap?
 

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DAMN you're lucky! I got quoted at $500 for the installation alone! I'm not sure if it's a direct swap, but I think so.
Tell me how it goes. I'm trying to convince my dad to let me switch diffs with my mom's auto 328i (3.46:1). :D
 

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ok this is probably a stupid question, but what are the benefits of switching diffs? for example i have a 323ci 5-speed, what would the effects be if i were to go to a larger or smaller one?
 

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I'm still looking for a 3.46 for my '99 323i (E46). I was supposed to get a 3.46 last week, but the junk yard selling it thought it was a 3.46, but it ended up being a 2.93 (I had to clear off the dirt and I saw the sticker). So, it didn't happen. :-(

Frank
 

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Discussion Starter · #16 ·
Ok so here's the real question, what kinda of rpm's am i going to be running at 80mph with 235/35/19s with 3.46:1. I've got stock 225/55/16s now and @ 80 mph i'm turning close to 3400rpm with 3.07:1s,

4000rpm with 3.:46?

Anyone know the equation my 5th gear is 1:1
 

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jco said:
Ok so here's the real question, what kinda of rpm's am i going to be running at 80mph with 235/35/19s with 3.46:1. I've got stock 225/55/16s now and @ 80 mph i'm turning close to 3400rpm with 3.07:1s,

4000rpm with 3.:46?

Anyone know the equation my 5th gear is 1:1
Try going to http://www.my330i.com/gears.php . It's a gear spead/shift calculator. I don't know how accurate it is, but it should provide some useful estimates.:dunno:
 

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frank,
how does the whole thing work, im curious to this mod and it seems like a good idea. and btw the 323 is not so slow to me. my previous car was an automatic civic.... so i still find it hella fast :)
 

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UNCG323ci said:
frank,
how does the whole thing work, im curious to this mod and it seems like a good idea. and btw the 323 is not so slow to me. my previous car was an automatic civic.... so i still find it hella fast :)
I'm not frank but changing the differential gear ratio changes your car's overall gear ratios. Which basically changes how fast the engine has to spin to make the wheels turn at any given speed. A funny thing is that a higher numerical ratio, like 3.46 vs. 3.07 is called a lower gear ratio when you are talking about it.

Anyway, the concept of gear ratio is directly related to the amount of work applied at one end of the gear set and the amount of work available at the other end. Know how a lever works, right? A small effort exerted on the long end of a lever can exert a great force on the short end. The longer the long end is, the greater the force multiplication is. The trade off is that you have to move the long end a large distance with little force to move the short end a short distance with great force. Gears work the same way, except for rotational motion instead of linear motion.

A lower gear ratio (i.e., numerically higher) is like using a longer lever to increase force. More force is applied to the wheels (as torque), but the engine has to move farther (as increased RPMs).

Switching from a 3.07 ratio to a 3.46 increases rear wheel torqe by about 12.7%. (it DOES NOT increase the amount of torque put out by the engine, it just changes the torque multiplcation factor the driveline provides) It also increases the RPMs necessary to maintain a given speed by 12.7%.

Hmm, that got kind of long...
 

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Sick post slow323ci :thumbup:
Very informative - I've always wondered what the figures were for how much more torque a 3.46 would put to the ground. Thanks!
 
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