[CobraMarty]

Here are the available ratios- 3 Series - E9x

328i MT- 3.23, also 325i MT
328i Auto- 3.73, also 325i Auto
328xi MT- 3.38, also 325xi MT
328xi Auto- 3.91, also 325xi Auto

330 MT- 3.15 (i or xi)
330 Auto- 3.64 (i or xi)

335 MT- 3.08 (i or xi)
335 Auto- 3.46 (i or xi)
M3- 3.85
335d- 2.81

If you have a 328 2WD i version, you have all the different rear diff ratio options.
If you have the 328 AWD xi version, your diff ratio choices are limited because you need a matching front diff ratio. Available ratios are 3.08, 3.38, 3.46, 3.91.

I have a 328xi MT which has the 3.38 diff ratios.
Yesterday I scored front and rear diffs from a 328xi Auto with 3.91 diff ratios for $300 shipped complete with drive shaft and axle flanges.

I am going to swap out the front and rear diffs with the 3.91 ratio diffs.

No LSD at this time. The 328 is HP limited (compared to 335) and no real rear traction problem especially with the xi front diff/traction.
If traction does become an issue, I will install a Quaffe or Wavetrac diff in the rear. $$ VAC gets $2200-2500 to rebuild the rear diff and add the LSD. Not going to spend that money now.

[stewey]

Thanks for the list. You might want to add entries for the 330 and 325.

[mike-y]

the 325i shares the same ratios as the 328i.

Not sure about the 330i vs 335i tho.

[CobraMarty]

I have a 328xi, but I added the 325 and 330 for you guys.
But for what fits what, IDK.

I expect my '07 328xi MT 3.38:1 will accept the '08 328xi Auto 3.91:1 diffs, just bolt in.

[Jashley73]

Good to know. Thanks for posting!

[CobraMarty]

Originally Posted by vha27

Correct, for a RWD only. XI version is a little different.
http://www.bokchoys.com/differential/GearRatios.htm

Here is where I found the info. Thanks and credit to vha27.

It was this info that gave me the idea to swap the 328xi auto 3.91 into my 328xi MT 3.38.

[CobraMarty]

Got the 2 diffs yesterday UPS. Both in one box 105 pounds total. The front is surprisingly small and light, rear obviously cast and bigger and heavier.
I will look closer at them later.

[328XIdiot]

Any update? Rear diff swap seems easy, but the front?

[CobraMarty]

Haven't started yet. Need to install the lift in the garage first.

[328XIdiot]

Well...a lift should help a lil

[bmwstandfor]

Originally Posted by CobraMarty

Here are the available ratios- 3 Series - E9x

328i MT- 3.23, also 325i MT
328i Auto- 3.73, also 325i Auto
328xi MT- 3.38, also 325xi MT
328xi Auto- 3.91, also 325xi Auto

330 MT- 3.15 (i or xi)
330 Auto- 3.64 (i or xi)

335 MT- 3.08 (i or xi)
335 Auto- 3.46 (i or xi)
M3- 3.85
335d- 2.81

If you have a 328 2WD i version, you have all the different rear diff ratio options.
If you have the 328 AWD xi version, your diff ratio choices are limited because you need a matching front diff ratio. Available ratios are 3.08, 3.38, 3.46, 3.91.

I have a 328xi MT which has the 3.38 diff ratios.
Yesterday I scored front and rear diffs from a 328xi Auto with 3.91 diff ratios for $300 shipped complete with drive shaft and axle flanges.

I am going to swap out the front and rear diffs with the 3.91 ratio diffs.

No LSD at this time. The 328 is HP limited (compared to 335) and no real rear traction problem especially with the xi front diff/traction.
If traction does become an issue, I will install a Quaffe or Wavetrac diff in the rear. $$ VAC gets $2200-2500 to rebuild the rear diff and add the LSD. Not going to spend that money now.

I bought the 328xi Auto- 3.91, now try to fit on my 328i 2wd 6spd but I found out that triangle piece not same as my differential, mine is the circle one, how can I fit it on? anyone can help?

[GTKrockeTT]

Originally Posted by bmwstandfor

I bought the 328xi Auto- 3.91, now try to fit on my 328i 2wd 6spd but I found out that triangle piece not same as my differential, mine is the circle one, how can I fit it on? anyone can help?

get the input flange swapped out between the two.

[bmwstandfor]

Originally Posted by GTKrockeTT

get the input flange swapped out between the two.

so after I swap the input flange that centre silver steel piece not stick out anymore? Because my diff dont have anything stick out from the centre

[GTKrockeTT]

i don't recall that section protruding from either of the diffs i had.

[E90_slides]

Originally Posted by CobraMarty

Here are the available ratios- 3 Series - E9x

328i MT- 3.23, also 325i MT
328i Auto- 3.73, also 325i Auto
328xi MT- 3.38, also 325xi MT
328xi Auto- 3.91, also 325xi Auto

330 MT- 3.15 (i or xi)
330 Auto- 3.64 (i or xi)

335 MT- 3.08 (i or xi)
335 Auto- 3.46 (i or xi)
M3- 3.85
335d- 2.81

If you have a 328 2WD i version, you have all the different rear diff ratio options.
If you have the 328 AWD xi version, your diff ratio choices are limited because you need a matching front diff ratio. Available ratios are 3.08, 3.38, 3.46, 3.91.

I have a 328xi MT which has the 3.38 diff ratios.
Yesterday I scored front and rear diffs from a 328xi Auto with 3.91 diff ratios for $300 shipped complete with drive shaft and axle flanges.

I am going to swap out the front and rear diffs with the 3.91 ratio diffs.

No LSD at this time. The 328 is HP limited (compared to 335) and no real rear traction problem especially with the xi front diff/traction.
If traction does become an issue, I will install a Quaffe or Wavetrac diff in the rear. $$ VAC gets $2200-2500 to rebuild the rear diff and add the LSD. Not going to spend that money now.

So if I wanted to buy a M3 e92 MT rear diff and slap it on my 328i MT RWD it will bolt right on?

[E90_slides]

Originally Posted by bmwstandfor

I bought the 328xi Auto- 3.91, now try to fit on my 328i 2wd 6spd but I found out that triangle piece not same as my differential, mine is the circle one, how can I fit it on? anyone can help?

that's because you bought an xi (AWD) differential. AND its and automatic and you said you have a 6sp MT? wouldn't fit anyways and you're downsizing in performance. get a MT rear diff RWD and you should be cherry. I've been looking at hundreds of pictures comparing stock 328i MT differentials to other stock MT diffs from other models. looks like I'm going to buy an m3 T LSD for $800

[drw1710]

Is it possible to swap the rear diff as a complete unit from an E9XX into an e46?. I am new to the BMW scene but not to hot-rodding and this seems like the perfect platform for the swap. Also, do any of these cars have an LSD option to look for?

[Phil325i]

OP, just for completeness as a guide for diffs, it's worth pointing out that your figures are for the US market. Diff ratios are different in Europe. For example my E92 325i manual with the N53 direct injection engine (which is quite torquey) has a diff ratio of 3.07.

[ZimZimmmmer]

Originally Posted by Phil325i

OP, just for completeness as a guide for diffs, it's worth pointing out that your figures are for the US market. Diff ratios are different in Europe. For example my E92 325i manual with the N53 direct injection engine (which is quite torquey) has a diff ratio of 3.07.

Good to.see another BMW'er from South East London!

Thanks for pointing out the above... Where would I be able to find out the Europe equivalent. I have an 330i N52 Auto which has a diff ratio of 3.64 but I want to change it to either 3.73 or 3.91 and wanted to know if it was possible or what my options are?

Thanks.

[Phil325i]

Originally Posted by ZimZimmmmer

Good to.see another BMW'er from South East London!

Thanks for pointing out the above... Where would I be able to find out the Europe equivalent. I have an 330i N52 Auto which has a diff ratio of 3.64 but I want to change it to either 3.73 or 3.91 and wanted to know if it was possible or what my options are?

Thanks.

SE England actually! If you go into RealOEM, the values for each diff are given. You'll have to try different models. Mine, for example you click on 'Rear Axle' then 'Rear-Axle-Drive' and for the diff it shows the part number and in the column headed 'Supp' it shows 'i=3,07'. For automatics it's 3.46.

Hope that helps.

[ZimZimmmmer]

Originally Posted by Phil325i

SE England actually! If you go into RealOEM, the values for each diff are given. You'll have to try different models. Mine, for example you click on 'Rear Axle' then 'Rear-Axle-Drive' and for the diff it shows the part number and in the column headed 'Supp' it shows 'i=3,07'. For automatics it's 3.46.

Hope that helps.

Hahaha close enough! Sorry if I didn't explain what I am after properly or maybe I don't understand your explanation in respect of what I am looking for.

I have used the Realoem website before and found the information you have explained. However, the information given/shown are parts for your specific car based on factory settings. Because I am looking to modify/change parts that are "not seen" as factory settings it doesn't give me a list of parts that can be applied to that specific vehicle.

In my example, Realoem had confirmed that my model (E92 330i AT N52) rear diff is 3.64. What it doesn't tell me is if a diff ratio 3.73 / 3.91 is compatible or would I have problems trying to install it?

I had stumbled upon this thread a few days ago which answered some of the questions I mentioned above that is, until, I saw your comment about the different variants based on US and UK equivalent. I am now stuck again searching for an answer to my question.

I came across this website that sort of answers my question based on the options it allows you to select but again they are based in the US. https://diffsonline.com/collections/...ction-products

Question: What diff range does my vehicle go up and down to? And if I brought a diff 3.73 or 3.91 would I be able to install/swap it for my factory (stock) 3.64 diff version without any incompatibility problems?

My Vehicle: 2007 330i N52 E92, Auto Trans.

I have found another thread in the same ballpark that I might as well link together...

https://www.e90post.com/forums/showthread.php?t=287472

Nevertheless, if you do or don't have the answer. Thanks for replying.

[Phil325i]

Your question is above my pay grade I'm afraid. My gut feeling would be that fitting any diff originally made for an E9X would be possible. The only difference would be the cutting of the internal gears to create the different ratios available. Sounds like you need to speak to a gearbox/transmission specialist.

One thought would be to chat to Birds https://www.birdsauto.com/ I contacted them when I was considering fitting a Quaife limited slip diff and they seemed to know their stuff on all matters differential...