calling all dif swappers...

[solo the lad]

I'm considering swapping my dif (06 n52 3.0 manual) to something with a higher final drive for a little more neck breaking action, and so that I can spend more in gas. I believe I have the 3.46, and im thinking I want to go up to 3.91 (those can be sourced from the e46's right?). So I would like to know:

what ratio did u swap to?
where did u source your dif from?
is the difference actually noticeable?
will I still lose races?

thanks.

[GuidoK]

Which car do you exactly have? the n52 in 3.0i trim or the n52 in 3.0si trim?
The (manual) n52 in 3.0i has a 3.38 final drive and the (manual) n52 in 3.0si has a 3.23 final drive according to the spare parts catalog.
So I think there's no possibility you have 3.46

3.91 is afaik a ratio used in the e36, not the e46.

Are you gonna do the swap yourself?

What kind of races are you loosing at the moment?

[Piper1]

There’s a thread think buried now with this: https://web.archive.org/web/20200729...calculator.htm

[GuidoK]

Yes, X3 diffs might be a drop in replacement. e8x 1 series not.
The x3 was fitted with a 3.91 ratio

That said, you can only use the 3.91 from the manual 2.5i and 3.0in52. the automatics 3.91 have a 168 diff, not 188 according to the parts catalog.
Those differences are not in that specsheet but is crucial for fitment.

[solo the lad]

Originally Posted by GuidoK

Which car do you exactly have? the n52 in 3.0i trim or the n52 in 3.0si trim?
The (manual) n52 in 3.0i has a 3.38 final drive and the (manual) n52 in 3.0si has a 3.23 final drive according to the spare parts catalog.
So I think there's no possibility you have 3.46

3.91 is afaik a ratio used in the e36, not the e46.

Are you gonna do the swap yourself?

What kind of races are you loosing at the moment?

Yes I would do the swap myself. Im assuming its just ratcheting work so should be fairly straightforward. I don't actually lose races because I live in a small town and no one races here :/

[Piper1]

Originally Posted by GuidoK

Yes, X3 diffs might be a drop in replacement. e8x 1 series not.
The x3 was fitted with a 3.91 ratio

That said, you can only use the 3.91 from the manual 2.5i and 3.0in52. the automatics 3.91 have a 168 diff, not 188 according to the parts catalog.
Those differences are not in that specsheet but is crucial for fitment.

Just in case, I hadn’t posted that pic suggesting those on there not e86/86 are compatible with one another. I just cropped the pic from the very long chart it is from the linked website and saved it from how it’s listed because I have an E82 too.

[solo the lad]

Originally Posted by GuidoK

Yes, X3 diffs might be a drop in replacement. e8x 1 series not.
The x3 was fitted with a 3.91 ratio

That said, you can only use the 3.91 from the manual 2.5i and 3.0in52. the automatics 3.91 have a 168 diff, not 188 according to the parts catalog.
Those differences are not in that specsheet but is crucial for fitment.

Im not sure im understanding how the final drive number is attained from the other numbers, based on the chart im looking at. Does the final drive ratio have an effect in all gears?

[Piper1]

Originally Posted by solo the lad

Im not sure im understanding how the final drive number is attained from the other numbers, based on the chart im looking at. Does the final drive ratio have an effect in all gears?

Yes. That’s why I linked the page I did. It’s plug and play to find out your top revs per gear. Going higher number on your final drive gear ratio cuts into top speed per gear. When up shifting your rpm drops less than your previous final drive ratio keeping you in a higher power band hence you’re in each gear shorter durations.

I swapped to a lsd from diffsonline to a 4.10 and 1st if you blink you’re already in 2nd. There’s times it’s beneficial times it’s not. One track by me has a long straight I can utilize 4th, another track I was at for the first time last year the longest straight I barely kissed 4th so it made more sense to back off than up shift and down shift as soon as you were to upshift. It all depends what you’re wanting to obtain from changing your final drive gear. I also added an ess vt1 when doing my diff so there’s very madness to the meaning.

[GuidoK]

Originally Posted by Piper1

I also added an ess vt1 when doing my diff so there’s very madness to the meaning.

I have an ESS TS2+ which makes fantastic torque pretty much from idle.
I drive with the stock 3.07 and 1st gear is completely useless.
If any I'd like a longer 1st gear, 2nd gear is fine and 3-4-5 could be more close ratio for spirited driving, and I'd like 6 to be much longer, as a cruise gear on the highway.
Too bad it's virtually impossible to change the gearbox ratio's without breaking the bank.

[GuidoK]

Originally Posted by solo the lad

Im assuming its just ratcheting work so should be fairly straightforward.

That greatly depends on what exact diff you're choosing.

[cbpip]

07 3.0 si manual, Switched to a 3.73 , 5 disc clutch type diff. Car is still drivable at hwy speeds , very reactive to acceleration at speed.
five, 104mm diameter friction discs ( type 188K discs are normally only 90mm) , for longevity , as a result of less load per square mm over time
- maintained static , set to 35% ( 110Nm) as your baseline for best case inside wheel spin control, without generating any oversteer
- asymmetrical dynamic locking (throttle controlled) favoring accel ( from 35% up to 100% , if called upon), over decel ( limited to 60% max) to avoid rear wheel lockup during hard decel

Custom diff by Jim Blanton at Performance Gearing, great guy and very knowledgeable on on how to set up diffs, great warranty and best prices for complete drop in diffs.

[cbpip]

Use this gear ratio calculator to figure out your max speeds for each gear using whichever final ratio you choose. Make sure to use either the correct Manual or automatic gearing ratios. And change the tire size to match yours.

E86Z4 3.0si / M Coupe Manual
I: 4.35 II: 2.50 III: 1.66 IV: 1.23 V: 1.00 VI: 0.85 Reverse: 3.93
Final Drive: 3.46:1
Redline: si 7,000 / M 8000

E86Z4 3.0si / 3.0i Coupe Auto
I: 4.17 II: 2.34 III: 1.52 IV: 1.14 V: 0.87 VI: 0.69VII: -Reverse: 3.40
Final Drive: 3.64:1 / 3.73:1
Redline: 7,000

https://web.archive.org/web/20200729...calculator.htm

[3002 tii]

On my old 3.0si manual I swapped in a 3.73 from a Z4 auto and it was the best balance for street and track. It was still driveable on street while giving me the much needed torque coming out of low speed turns (i.e. hairpins) on track. Best part was it was quite cheap as I didn’t need to rebuild anything; it was direct swap.

[cbpip]

3.73 from an Z4 auto would have been an open diff not an LSD.

[Piper1]

Originally Posted by GuidoK

I have an ESS TS2+ which makes fantastic torque pretty much from idle.
I drive with the stock 3.07 and 1st gear is completely useless.
If any I'd like a longer 1st gear, 2nd gear is fine and 3-4-5 could be more close ratio for spirited driving, and I'd like 6 to be much longer, as a cruise gear on the highway.
Too bad it's virtually impossible to change the gearbox ratio's without breaking the bank.

Ooohhhhhh I had the TS in my shopping cart for a long time and with how it builds boost there wasn’t even an angel/devil shoulder scenario it was the image of the Mrs behind me if something ever went wrong not being able to duck fast enough getting a back hand then an I told you so lol. Come close many occasions with some wrinkles and hiccups along the way where I’ve gotten from her the I knew it woman’s scorn and my follow up being buuut honey I fixed it being how my budget was back then it was the same price getting the lsd built from diffsonline went 3 clutch 35/60 ramps plus the VT compared to just the cost of the TS so figured the 4.10 would make the VT very happy when really wanting to get on it at the same time the Mrs could be happy in just the piddle around town knowing wouldn’t get too crazy day to day with boost. Totally agree on the gearbox. We need that happy place utilizing each gear a bit better. The track I was at last year for the most part just kept it in 3rd a vast majority of the time, so yeah get fourth a little closer in and 4th would be happy on the back straight there.

[3002 tii]

Originally Posted by cbpip

3.73 from an Z4 auto would have been an open diff not an LSD.

Yea no kidding. OP didn’t ask about limited slip.

[solo the lad]

Originally Posted by 3002 tii

On my old 3.0si manual I swapped in a 3.73 from a Z4 auto and it was the best balance for street and track. It was still driveable on street while giving me the much needed torque coming out of low speed turns (i.e. hairpins) on track. Best part was it was quite cheap as I didn’t need to rebuild anything; it was direct swap.

This was the info I was looking for, thanks. So I can get that dif from any automatic e85 z4 and it will fit mine? (06 3.0i manual)

[3002 tii]

Originally Posted by solo the lad

This was the info I was looking for, thanks. So I can get that dif from any automatic e85 z4 and it will fit mine? (06 3.0i manual)

Correct