[desertman123]

Do I have to look for a specific model or will literally any E9x 328i auto diff simply bolt in? I can find those all day on eBay with under 100k mile for ~$200.

Also if I swap it myself, do I need any specialty tools besides the usual BMW toolkit?

[Ali-E90]

I had a friend accidentally get an Xdrive diff which wouldn't work. Make sure you get the right one in terms of AWD/RWD.

Don't know with regards to any additional criteria to look for.

[Volasko]

Originally Posted by desertman123

Do I have to look for a specific model or will literally any E9x 328i auto diff simply bolt in? I can find those all day on eBay with under 100k mile for ~$200.

Also if I swap it myself, do I need any specialty tools besides the usual BMW toolkit?

No special tools required. Pretty easy job. Only problem will be removing the exhaust that gets in the way expecially if you are stock. I had a PE exhaust with pipe clamps so it helped make my life easier. You will need some torx sockets to remove the half shafts, which most people should have anyways. Worth the effort though really makes the car feel alive.

[desertman123]

Originally Posted by Volasko

No special tools required. Pretty easy job. Only problem will be removing the exhaust that gets in the way expecially if you are stock. I had a PE exhaust with pipe clamps so it helped make my life easier. You will need some torx sockets to remove the half shafts, which most people should have anyways. Worth the effort though really makes the car feel alive.

Looks like I'll do it myself then. I got Torx/Etorx anyway. For the exhaust I might as well be stock - I just have a muffler delete which is welded. Someone mentioned I needed like a 50mm to get the driveshaft out? Was I reading it wrong or do I need that? Otherwise I have everything I'll need.

[avocet]

I think the 50 mm is for removing the input flange... if you are using a 328i diff you should not have to remove it. If you get a 330I 3.64 diff your flange will be different, and you will be required to swap it.

[Biginboca]

I just did this swap last weekend. Bought a e90 328i auto Diff 3.73 off eBay for $230 delivered. Made a huge difference in my e92 manual! Swapping the Diff was very easy can be done in less than 2 hours if you know your way around a car. Definitely have a buddy help you it's hard to line up the Diff, work the jack, and slip the bolts in alone. (Probably impossible to do that part alone.)

On mine I didn't have to mess with the factory exhaust at all. Just had to unbolt the end of one heat shield (near the Driveshaft flange) and bend the heat shield back a bit to get to the Driveshaft flange bolts. Outside of that single 10mm Bolt the only other bolts I turned were the 3 Diff mounting bolts (2 x 18mm and 1 x 21mm), the Torx half shaft bolts, and the Torx Driveshaft bolts.

I also swapped diff bushings to the m factory ones that added about 2 hours to the job.

You won't regret this swap!

[Joebie]

Quick question about this swap, won't your mileage be exaggerated by about 15%?

I'm interested in this mod as well, but I've read that the odometer gets its reading from the transmission, not the wheels, which would mean that the car would have no way of knowing you're actually covering less distance per revolution with the new diff, right?

[W37V]

Originally Posted by Joester

Quick question about this swap, won't your mileage be exaggerated by about 15%?

I'm interested in this mod as well, but I've read that the odometer gets its reading from the transmission, not the wheels, which would mean that the car would have no way of knowing you're actually covering less distance per revolution with the new diff, right?

No, it will not affect the odo.

[Joebie]

Originally Posted by W37V

No, it will not affect the odo.

Thanks, can you explain why? Am I wrong about the odo taking its measurement from the transmission?

[W37V]

Originally Posted by Joester

Thanks, can you explain why? Am I wrong about the odo taking its measurement from the transmission?

see here:
http://www.e90post.com/forums/showthread.php?t=1353199

[Joebie]

Originally Posted by W37V

see here:
http://www.e90post.com/forums/showthread.php?t=1353199

Awesome, thanks. For anyone who comes across this thread later, it seems like the speedo and odo get their signal from the left rear wheel, not the transmission like I thought.

This manual-->auto diff swap seems like a pretty low risk mod, they are all over ebay for $200 or so and I've yet to see someone say they didnt enjoy the car after doing this.

[Joebie]

So uhh I just impulse bought a 3.73 diff for $130 shipped. Came out of a 2011 with 60k miles that had been in a front end accident.

Figured if I don't like it its only $130! We'll see how this goes.

[desertman123]

Originally Posted by Joester

So uhh I just impulse bought a 3.73 diff for $130 shipped. Came out of a 2011 with 60k miles that had been in a front end accident.

Figured if I don't like it its only $130! We'll see how this goes.

Post a few pics of the install if you're gonna DIY!

Originally Posted by Biginboca

I just did this swap last weekend. Bought a e90 328i auto Diff 3.73 off eBay for $230 delivered. Made a huge difference in my e92 manual! Swapping the Diff was very easy can be done in less than 2 hours if you know your way around a car. Definitely have a buddy help you it's hard to line up the Diff, work the jack, and slip the bolts in alone. (Probably impossible to do that part alone.)

On mine I didn't have to mess with the factory exhaust at all. Just had to unbolt the end of one heat shield (near the Driveshaft flange) and bend the heat shield back a bit to get to the Driveshaft flange bolts. Outside of that single 10mm Bolt the only other bolts I turned were the 3 Diff mounting bolts (2 x 18mm and 1 x 21mm), the Torx half shaft bolts, and the Torx Driveshaft bolts.

I also swapped diff bushings to the m factory ones that added about 2 hours to the job.

You won't regret this swap!

Thanks so much for the info. Seems like this is a low risk, high reward mod. I do a lot of highway cruising so that'll suffer a tiny bit, but I'm not concerned.

Doing the math, a 3.23 to 3.73 is a 15.4%, actually increase. Meaning at 80mph, with a 3.23 I'll be at ~2900 RPM, while with the 3.73 I'll be pulling ~3400rpm. Not bad at all. I'm sure 1st and 2nd gear will RIP, and it'll liven up 3rd and onward. Good little intermediate mod before I can get the heavy hitting 3stage/tune/headers.

Thanks for the info on the 3.64 diff too, I was looking at those to be a little more tame, but they're way less bountiful than the 3.73 and requires a bit more effort on install. For such a minute difference I'll just get the 3.73.

My process might be a little different being I have a 1-series. May or may not have to remove the exhaust, we'll see.

[Joebie]

Originally Posted by desertman123

Post a few pics of the install if you're gonna DIY!



Thanks so much for the info. Seems like this is a low risk, high reward mod. I do a lot of highway cruising so that'll suffer a tiny bit, but I'm not concerned.

Doing the math, a 3.23 to 3.73 is a 13.4% increase. Meaning at 80mph, with a 3.23 I'll be at ~2900 RPM, while with the 3.73 I'll be pulling ~3300rpm. Not bad at all. I'm sure 1st and 2nd gear will RIP, and it'll liven up 3rd and onward. Good little intermediate mod before I can get the heavy hitting 3stage/tune/headers.

Thanks for the info on the 3.64 diff too, I was looking at those to be a little more tame, but they're way less bountiful than the 3.73 and requires a bit more effort on install. For such a minute difference I'll just get the 3.73.

My process might be a little different being I have a 1-series. May or may not have to remove the exhaust, we'll see.

I will post pics, I'll probably create a DIY thread but I'll link it here.

Also, 3.73/3.23=1.155, so that's a 15.5% increase in revs and torque. Just being nitpicky.

[Biginboca]

After the 3.73 swap 90mph = 3750rpm in 6th gear. And top speed would still be above the governed speed.



https://flic.kr/p/VpbF5V

My mileage was unaffected as far as I could tell but I'm mostly city driving. Highway driving was a newfound pleasure I never needed to downshift the pulling power in 6th is awesome. 1st gear is totally usable and you can actually get a good dig. Much improved. 1st to 2nd drops you into the dead spot around 4500 so unless you have a tune to get into the redline a little before shifting to second it's annoying. (This has nothing to do with the Diff it was the same before the Diff lol.)

2-3rd gear upshifts tons of fun you stay in the power above 5k RPM and it really pulls noticeably harder in 3rd.

I can't imagine anyone feeling this isn't money and time well invested. It's cheaper than the 3IM mod, needs no tune or accompanying mods, and makes a change you really can feel. I can't think of a single downside!

[desertman123]

Originally Posted by Joester

I will post pics, I'll probably create a DIY thread but I'll link it here.

Also, 3.73/3.23=1.155, so that's a 15.5% increase in revs and torque. Just being nitpicky.

Whoops you're right, I mixed up the formula for % change in my head.

((new-old)/old)*100
((3.73-3.23)/3.23)*100 = 15.5% increase

I'd love a DIY! I'm sure I can figure it out myself but a guide (even without pics) is always nice.

Originally Posted by Biginboca

After the 3.73 swap 90mph = 3750rpm in 6th gear. And top speed would still be above the governed speed.



https://flic.kr/p/VpbF5V

My mileage was unaffected as far as I could tell but I'm mostly city driving. Highway driving was a newfound pleasure I never needed to downshift the pulling power in 6th is awesome. 1st gear is totally usable and you can actually get a good dig. Much improved. 1st to 2nd drops you into the dead spot around 4500 so unless you have a tune to get into the redline a little before shifting to second it's annoying. (This has nothing to do with the Diff it was the same before the Diff lol.)

2-3rd gear upshifts tons of fun you stay in the power above 5k RPM and it really pulls noticeably harder in 3rd.

I can't imagine anyone feeling this isn't money and time well invested. It's cheaper than the 3IM mod, needs no tune or accompanying mods, and makes a change you really can feel. I can't think of a single downside!

I'm mostly city driving too so good to know it won't change.

And yeah I fully expected to relearn how to rip the car. Is 1st gear touchy or is it still pretty manageable? And that deadspot at 4.5k is just an excuse to get headers, 3IM and a tune .

Would you be able to make a quick video of how the car moves now? Once I get my diff in I'll make like a 5-80mph pull.

[Biginboca]

Originally Posted by desertman123

Whoops you're right, I mixed up the formula for % change in my head.

((new-old)/old)*100
((3.73-3.23)/3.23)*100 = 15.5% increase

I'd love a DIY! I'm sure I can figure it out myself but a guide (even without pics) is always nice.




I'm mostly city driving too so good to know it won't change.

And yeah I fully expected to relearn how to rip the car. Is 1st gear touchy or is it still pretty manageable? And that deadspot at 4.5k is just an excuse to get headers, 3IM and a tune .

Would you be able to make a quick video of how the car moves now? Once I get my diff in I'll make like a 5-80mph pull.

After I installed the Diff 2 days later (July 3rd) I let it ripp in 1st gear making a U turn. The power was there and the car got sideways both ways I jumped a curb and now it's in the bodyshop. I had the traction control off and am now paying the price battling with insurance company who wants to total loss the car. I'm making a strong case to get it fixed it's just plastic body panels, headlights, and some control arm damage. Unfortunately because these cars are aging and bmw parts are expensive they total easily.

But it looks like things are going my way and hopefully in a few weeks I can post video. 1st gear is not jumpy. It's actually perfect. Every gear is perfect with the 3.73 IMO. Others have said and I agree it's what the car should have come with from the factory.

[Volasko]

Originally Posted by desertman123

Would you be able to make a quick video of how the car moves now?

I took a quick and dirty video doing a quick 1-2 shift. My car has the 3IM (already a 330i) and AA tune:

https://drive.google.com/file/d/0B8p...ew?usp=sharing

[Joebie]

I got my 3.73 in the mail yesterday, will be installing over the weekend. Maybe tonight if I feel like it but we'll see.

[Joebie]

Here's my thread on the subject

http://www.e90post.com/forums/showthread.php?t=1403625