[X330I]

So as many of you know i blew my front diff due to mix match rim size. Im in search of a front differential for my 06 330xi 6mt and its not easy to find as it is a rare match. Only 2 other cars supposedly come with the same diff 530xi and 328xi coupe (both manual).

I recently got in contact with a guy from Project M Motors from NJ, he told me the 335xi 6mt will work and he installed them on plenty of 330/328 with no problems. i did a little digging to find out the ratios and they are all different but mine being the closest 3.08(330xi)/3.15(335xi).

Before i take the plunge i wanted to come in here and get opinions. Since he is 100% certain and he installed them all around i assume he knows what he talking about. I'm trying to find a front diff that would work asap. Can anyone confirm or point me in the rite direction ?

THANKS FOR ALL YOUR HELP!!!

[ajsalida]

Are you kidding me? That is ridiculous. You already wrecked your front diff installing mismatched tire sizes now you want to "fix" that by installing a mismatched F/R diff ratios??? You'll wreck the transfer case next if it even drives. You are not supposed to run tires more than 1% diameter difference, that ratio difference is over 2%. So even if you tires are perfectly equal sizes you'll be running major slip thru the transfer case all the time.

Look, either find a diff the right ratio or park this car. One thing you could do is find a front diff that fits and swap both front and rear diffs to match the new front ratio. If the 335 3.15 fits in front find a 335 3.15 rear, swap both. 335 rear diffs are not that expensive, as little as $200. Maybe this is what the guy means when he says he swaps the 335 diff in, both F&R? I really hope I misunderstood.

PLEASE do not mix front/rear diff ratios, I can't believe I even have to say this.

[X330I]

Thanks for the help, I'm not as knowledgeable about this whole awd thing so when someone that deals with only bmw's and has a whole shop full of them tells me something from his experience it seems legit.

I don't know any better that's why I came in here just to ask a question. He didn't mean he swap both diff, he told me exactly what I posted he put the 335 diff in plenty of other cars and vice versa. He also said the manual diff are really not that different. I asked him multiple times because I was un sure and he guaranteed me he does it all the time with no problem.

But thanks for steering me in the rite direction even tho it wasn't as pleasant.

[ajsalida]

Originally Posted by X330I

Thanks for the help, I'm not as knowledgeable about this whole awd thing so when someone that deals with only bmw's and has a whole shop full of them tells me something from his experience it seems legit.

I don't know any better that's why I came in here just to ask a question. He didn't mean he swap both diff, he told me exactly what I posted he put the 335 diff in plenty of other cars and vice versa. He also said the manual diff are really not that different. I asked him multiple times because I was un sure and he guaranteed me he does it all the time with no problem.

But thanks for steering me in the rite direction even tho it wasn't as pleasant.

Ask him why he thinks installing mismatched F/R diff ratios is going to be "fine".

Look I'm sorry your feathers are a bit ruffled but you're asking some very odd questions and repeatedly contemplating doing stuff that is flat out crazy/dangerous. And we have been telling you that but you're somehow not getting the point.

It is OK to not know something but you already badly messed up your car once installing mismatched tire sizes, then you wanted to take the axles out (which would make the front wheels fall off), then you wanted to drive it around with axles in but a front diff with no oil in it, now a mismatched F/R diff ratios?

We are trying to help you not kill yourself, which you seem intent on doing.

If you cannot find the right front diff for your 330xi, please look into swapping MT front and rear 335xi diffs (which BTW are both 3.08 ratio, not 3.15).

[X330I]

I was just trying to exhaust all options while not trying to have the car down for to long.

I never knew about the mismatched tire size thing with AWD until it happen. I did some research to find all the do's and dont. I never had or wanted an AWD car and now i really dont. To make matters worst this car was only produce in 2006 and not a lot was manual so my chances of stumbling across a manual diff are very slim.

I see you mentioned finding a manual 335 front and rear diff, does the rear have to be xi or can it be RWD ? How hard is it to change the rear diff on a xi car ? Does it bolt rite up or need some modification ? How much different in speed/acceleration ? Are automatic diff an option also ? Im just asking questions...

THANKS AGAIN!!!

[Fundguy1]

Try hp autosport. Harold can help.
Www.Hpashop.com

[X330I]

Originally Posted by Fundguy1

Try hp autosport. Harold can help.
Www.Hpashop.com

Should i contact him through the website or just look for the part ?

[Fundguy1]

I called and spoke to him directly. He's a good guy. They do sales on the phone too so you get exactly what you need. He's the boss but the regular sales guys would be fine for your problem. Just tell them you're e90post guy.

[ajsalida]

Originally Posted by X330I

I was just trying to exhaust all options while not trying to have the car down for to long.

I never knew about the mismatched tire size thing with AWD until it happen. I did some research to find all the do's and dont. I never had or wanted an AWD car and now i really dont. To make matters worst this car was only produce in 2006 and not a lot was manual so my chances of stumbling across a manual diff are very slim.

I see you mentioned finding a manual 335 front and rear diff, does the rear have to be xi or can it be RWD ? How hard is it to change the rear diff on a xi car ? Does it bolt rite up or need some modification ? How much different in speed/acceleration ? Are automatic diff an option also ? Im just asking questions...

THANKS AGAIN!!!

That's fine. As far as I know RWD rear diffs will bolt right up but I am not 100% certain. You'll have to check that axles are the same (MT and AT 335 rear axles are different, for example, and there are different pumkin sizes have no idea what your 330xi is). Bottom line check with someone (like Harold or say M-factory) who does diffs for a living and ask, maybe they have better ideas.

The AT 335xi diff is 3.46 IIRC so that will be quite a step down in gearing, making the revs higher for a given road speed. The MT 335xi 3.08 is close (assuming your car is 3.15), but taller, so you'll get slightly better mileage but slightly slower acceleration.

There may be some other solution out there, maybe your existing diff can be rebuilt I don't know. The point was if you are going to swap front diff for a different ratio you MUST swap rear diff to same ratio. I don't know anybody sane who would recommend otherwise. And before rushing off the eBay to buy 2 diffs, you'll need to look carefully into if everything else will fit or carry over, like axles, driveshafts, mounts etc.

[X330I]

Originally Posted by ajsalida

That's fine. As far as I know RWD rear diffs will bolt right up but I am not 100% certain. You'll have to check that axles are the same (MT and AT 335 rear axles are different, for example, and there are different pumkin sizes have no idea what your 330xi is). Bottom line check with someone (like Harold or say M-factory) who does diffs for a living and ask, maybe they have better ideas.

The AT 335xi diff is 3.46 IIRC so that will be quite a step down in gearing, making the revs higher for a given road speed. The MT 335xi 3.08 is close (assuming your car is 3.15), but taller, so you'll get slightly better mileage but slightly slower acceleration.

There may be some other solution out there, maybe your existing diff can be rebuilt I don't know. The point was if you are going to swap front diff for a different ratio you MUST swap rear diff to same ratio. I don't know anybody sane who would recommend otherwise. And before rushing off the eBay to buy 2 diffs, you'll need to look carefully into if everything else will fit or carry over, like axles, driveshafts, mounts etc.

I did some research and i came across a few threads saying the automatic 330 diffs bolt rite up. They do increase your accel but decrease the top speed.

I checked a local transmission rebuild shop they quoted me $1700 not sure if they meant taking it out plus parts, my mechanic is only charging me 300 for removal and install.

Tomorrow morning im gong to call the places yall gave me and get more info. As of rite now im going to stick with the auto diff for the front and rear unless anyone might want to chime in with fitment or other issues that come with this.

[pavproch]

As I wrote in the other thread, the AT diffs (3.64 ratio for both front - size 174 and rear - size 188) are a straight bolt-on.

With the shorter diffs in, the car will follow your gas pedal with ease....

I did this very swap some 4months ago and never regretted a single buck from a large pile of money it cost.

But, you can even multiply funfactor tenfold should you give LSD in (rear diff). I did.

[Fundguy1]

I wonder if they do lsd for front diff. Hmmmm

[PhaseP]

Op you may be better of with less headache and maybe even more cache when all said and done if you just order a rebuilt one from BMW. You will know that it will work and will have some warranty on it.