[max_330i]

I used the search function and found some previous threads on this topic, but I didn't want to resurrect any of them, so I'm creating a new one. I'm thinking of swapping the 3.15 differential in my manual 330i with a 3.64 differential from an automatic 330i. Based on my preliminary research, this should yield a 15% in rwtq at the cost of 15% higher revs in each gear-- if I am wrong about this please correct me.

Basically, I want to make the car feel quicker without significant cost. The part should run me a couple hundred bucks and I can do the work myself. Although they are hardly "mods," I already have the CDV delete, BMW SSK, and ZHP shift knob, which have greatly improved the experience of driving the car-- I feel like the diff swap will be along the same lines.

I mostly drive in the city so high revs on the highway is not a serious concern. I am also aware that gas mileage will suffer, and that I will be rowing through the gears faster and more often. Aside from the drawbacks I've listed, is there any particular reason I should avoid such a swap?

[ycehcky]

I want to do this as well. I think we have similar driving patterns, so it makes more sense than someone who does mostly highway driving.
I did notice when I was on the track, that i was stuck between 2nd and 3rd. Either leave it in 3rd or get a little squirrelly in 2nd if I didn't hit the downshift perfectly. I think with the 3.64 you would be in 3rd and 4th more, which is a much easier down shift.
The mere fact that you can do more than 60 mph in 2nd gear is silly to me. I say go for it and give some feedback, so I will finally bite the bullet haha.

[Volasko]

DO EET!! Best mod I have done hands down in making the car more fun to drive (see my garage for a complete list of what I have done). I do a lot of highway daily driving and I still don't regret it at all. I lost about 50km (600km per tank to about 550km) per tank in fuel economy but the added feeling of torque completely makes up for it. Yes you will be shifting more, but I don't see that as a bad thing. The pull in 2nd gear is addicting and really does liven up the car. I'm shocked more people haven't tried it to be honest. Not that hard of an install too. High speed cruising (+140 km/h) is compromised a little with exhaust drone and that weird uneasy feeling of seeing the tach so high up while maintaining a constant speed.

[max_330i]

Thanks for chiming in guys. Good insight.

Originally Posted by ycehcky

I want to do this as well. I think we have similar driving patterns, so it makes more sense than someone who does mostly highway driving.
I did notice when I was on the track, that i was stuck between 2nd and 3rd. Either leave it in 3rd or get a little squirrelly in 2nd if I didn't hit the downshift perfectly. I think with the 3.64 you would be in 3rd and 4th more, which is a much easier down shift.
The mere fact that you can do more than 60 mph in 2nd gear is silly to me. I say go for it and give some feedback, so I will finally bite the bullet haha.

I've done a couple of track days with my car also and found that second gear was just barely too low for a lot of the corners. I think you're right that I would be in 3rd and 4th more with the 3.64 diff. If/when I go through with the swap, I will definitely report back on the results

Originally Posted by Volasko

DO EET!! Best mod I have done hands down in making the car more fun to drive (see my garage for a complete list of what I have done). I do a lot of highway daily driving and I still don't regret it at all. I lost about 50km (600km per tank to about 550km) per tank in fuel economy but the added feeling of torque completely makes up for it. Yes you will be shifting more, but I don't see that as a bad thing. The pull in 2nd gear is addicting and really does liven up the car. I'm shocked more people haven't tried it to be honest. Not that hard of an install too. High speed cruising (+140 km/h) is compromised a little with exhaust drone and that weird uneasy feeling of seeing the tach so high up while maintaining a constant speed.

Glad to hear you like the change! And I agree that burning a little extra fuel for a little more torque is a worthy tradeoff. I love the 2nd gear pull in my car and I'm sure the 3.64 diff would make it pure bliss. I'm also surprised that more people don't talk about this mod, especially in the non-turbo drivetrain section-- it almost seems too good to be true-- swap one part with another OEM component and have more power on tap all the time. What's not to like?

[lab_rat]

I'm interested in this mod too; it seems like the biggest mechanical 'bang for the buck'.

[Manual Transmission]

I'm curious about this too, but I can't see myself doing it to be honest. Has anyone done the calculations to see where the tach would be at 60MPH and 80MPH in 5th and 6th?

[justpete]

Originally Posted by max_330i

I used the search function and found some previous threads on this topic, but I didn't want to resurrect any of them, so I'm creating a new one. I'm thinking of swapping the 3.15 differential in my manual 330i with a 3.64 differential from an automatic 330i. Based on my preliminary research, this should yield a 15% in rwtq at the cost of 15% higher revs in each gear-- if I am wrong about this please correct me.

Basically, I want to make the car feel quicker without significant cost. The part should run me a couple hundred bucks and I can do the work myself. Although they are hardly "mods," I already have the CDV delete, BMW SSK, and ZHP shift knob, which have greatly improved the experience of driving the car-- I feel like the diff swap will be along the same lines.

I mostly drive in the city so high revs on the highway is not a serious concern. I am also aware that gas mileage will suffer, and that I will be rowing through the gears faster and more often. Aside from the drawbacks I've listed, is there any particular reason I should avoid such a swap?

3500rpm at 85mph (I think) with a 3.73 diff replacing a 3.23 stock diff. Not a problem and much better on the track. No reason to avoid it, will at least get rid of the pointless overdrive gear in sixth assuming you don't take long highway trips.

[max_330i]

Originally Posted by lab_rat

I'm interested in this mod too; it seems like the biggest mechanical 'bang for the buck'.

Most certainly is. That's why I've started this thread. I'm making sure there are no fun surprises involved in a diff swap before I pull the trigger. So far so good.

Originally Posted by Manual Transmission

I'm curious about this too, but I can't see myself doing it to be honest. Has anyone done the calculations to see where the tach would be at 60MPH and 80MPH in 5th and 6th?

Originally Posted by justpete

3500rpm at 85mph (I think) with a 3.73 diff replacing a 3.23 stock diff. Not a problem and much better on the track. No reason to avoid it, will at least get rid of the pointless overdrive gear in sixth assuming you don't take long highway trips.

Sixth gear with the 3.15 diff in my car is way too tall. It's not useful anywhere except the highway, which makes it pretty obsolete given my route to work.

I'm not really focused on where the tach would be at any given cruising speed, but rather, the total increase in revs in each respective gear. That's why I quote 15% in my original post (3.64 / 3.15 = 1.15, roughly).

[ktm137]

Gotta find time to install my auto (3.64) diff with M-Factory LSD in for the 3.15 factory 330i diff.

When M-Factory was doing their recent sale, I was able to go to car-parts.com and find an auto 330i for only $150, and then ship it straight to M-Factory for them to inspect and install the LSD. A short while later a small, but heavy box arrived.

Now it sits in my garage waiting for time to install!

Like many other 330i owners, I have the SSK, ZHP know, CDV delete, but still wanted a bit more pull. I'm hoping this gives this.

I know I'll be running more revs on the freeway, but I'm expecting it to be worth it. :-)

Kevin M.
-06 330i MTX

[tlow98]

Nice! How march does an on sale one go for? I see about $1k normally?

Thanks

[ktm137]

If I remember correctly, it was basically $1150 or $1199

Basically, it was their complete Fully Rebuilt Core sale price minus the $500 core (since there is no exchange, and I'll keep my stock 3.15 pumpkin).

That included MFactory cleaning/inspecting/installing/shipping.

Kevin

[Volasko]

Originally Posted by Manual Transmission

I'm curious about this too, but I can't see myself doing it to be honest. Has anyone done the calculations to see where the tach would be at 60MPH and 80MPH in 5th and 6th?

With my current setup my RPM was 3600 at 140 kph (87 mph) in 6th gear.

[tlow98]

Originally Posted by ktm137

If I remember correctly, it was basically $1150 or $1199

Basically, it was their complete Fully Rebuilt Core sale price minus the $500 core (since there is no exchange, and I'll keep my stock 3.15 pumpkin).

That included MFactory cleaning/inspecting/installing/shipping.

Kevin

That's a solid package deal. Thanks for your reply.

[bigfellas_dad]

Nice mod, Id do it for sure as those revs are totally manageable even at distance. My first 1995 subaru impreza turbo was spec'd with lots of tarmac rally gear and cost me 150% of the value of the car in options alone The gearing allowed me to only get to 112mph flat out in top gear (7000rpm) and that was too tedious on anything other than country lanes. But on those lanes it was an absolute HOOLIGAN of a car!

[max_330i]

Update: 3.64 diff is sitting in my living room. DAMN, this thing is heavy!! Can't wait to install and do a couple 2nd gear pulls

[ycehcky]

Any possible way you could do a video of the speedo/rpm accelerating before and after. I know...I know what the before looks like haha.

[ktm137]

For those that have done the swap, or planning on doing it, are you replacing the diff mount bushings?

I haven't gotten the chance to do mine yet, but wanted to get bushings if it makes sense to do now, at 150k miles.

To the regard, preferences or recommendations on bushings?

[avocet]

Originally Posted by ktm137

For those that have done the swap, or planning on doing it, are you replacing the diff mount bushings?

I haven't gotten the chance to do mine yet, but wanted to get bushings if it makes sense to do now, at 150k miles.

To the regard, preferences or recommendations on bushings?

I used whiteline diff bushings. Am totally happy with them but haven't used any others.

I wouldn't do it without changing the bushings.

[max_330i]

Originally Posted by avocet

I used whiteline diff bushings. Am totally happy with them but haven't used any others.

I wouldn't do it without changing the bushings.

Where did you source diff bushings? I think the diff I ordered has them but I would rather replace with new.

Originally Posted by ycehcky

Any possible way you could do a video of the speedo/rpm accelerating before and after. I know...I know what the before looks like haha.

I can't promise that I'll have the time to do a before video but I will create one for the acceleration after the install

[lab_rat]

Can't wait to see the after video!

[max_330i]

The 3.64 diff is installed! First impressions: car definitely feels like it has more torque, it rips through the gears much faster than before and snaps my head back against the headrest no problem It is currently mid-30s in Chicago and not the best weather to be doing acceleration testing, so I am postponing the acceleration video until I have the chance to do it right... However if you are waiting to pull the trigger on this mod I say DO IT. Adds a lot of life to the car and a great value.

[Manual Transmission]

Originally Posted by max_330i

The 3.64 diff is installed! First impressions: car definitely feels like it has more torque, it rips through the gears much faster than before and snaps my head back against the headrest no problem It is currently mid-30s in Chicago and not the best weather to be doing acceleration testing, so I am postponing the acceleration video until I have the chance to do it right... However if you are waiting to pull the trigger on this mod I say DO IT. Adds a lot of life to the car and a great value.

Thanks for the update, I'm definitely looking forward to your video. I'd be curious to hear before and after 0-60 times. You're really making me want to do this, and I bet that differentials are cheap and plentiful at the wrecking yard...