Differential Time, 3.91 vs 4.10 on 6 speed ZCP

[Silbergrau metallic]

You say acceleration gain, but don't forget sometimes it's slower.

E.g. If you're going, say, 90mph. In a stock diff car you'd be in 3rd, in a 4.10 car you'd be in 4th. The stock gear car has more aggressive gearing at that speed, as a result.

People posting videos of gains from diffs like to compares same gear vs same gear at a given speed. In that situation, certainly, yes, a shorter diff is faster. But, it's not a particularity meaningful test.

If you compare optimal gear vs optimal gear... results may differ, depending on the speed you're going. The faster you're going, the more often the stock diff results in a more aggressive net ratio being possible. Plus the shorter ratio slows you down by requiring more frequent shifting.
(the constant shifting was why I nixed the 4.10s on the track car, though it was probably a bit of an extreme case at 2315 lbs. It was annoying and slower because of it)

That makes a lot of sense, I guess I'm just trying to get the most bang for my buck and I was considering gear ratios, since I need the Diff rebuilt and wanted opinions. Going from 3.62 to 3.91 or 4.10 Doubles the price of the Differential on Diffsonline and I'd rather use that money on a better than Stock LSD, like Wavetrac and go with the stock 3.62 ratio like you have done. Did you have the Ring, Pinion and Bearing polishing option added also or is that unnecessary and does the Wavetrac option require different 210mm Output flanges for the carrier. Sorry for all the questions, but I'm trying to make sure I order everything I need the first time.

[Obioban]

That makes a lot of sense, I guess I'm just trying to get the most bang for my buck and I was considering gear ratios, since I need the Diff rebuilt and wanted opinions. Going from 3.62 to 3.91 or 4.10 Doubles the price of the Differential on Diffsonline and I'd rather use that money on a better than Stock LSD, like Wavetrac and go with the stock 3.62 ratio like you have done. Did you have the Ring, Pinion and Bearing polishing option added also or is that unnecessary and does the Wavetrac option require different 210mm Output flanges for the carrier. Sorry for all the questions, but I'm trying to make sure I order everything I need the first time.

The polishing is unnecessary... but I did it. "While you're in there" got me on that one for sure :P

The Wavetrac does require different output flanges, though I forget the specifics of that at this point.

[bigjae46]

That makes a lot of sense, I guess I'm just trying to get the most bang for my buck and I was considering gear ratios, since I need the Diff rebuilt and wanted opinions. Going from 3.62 to 3.91 or 4.10 Doubles the price of the Differential on Diffsonline and I'd rather use that money on a better than Stock LSD, like Wavetrac and go with the stock 3.62 ratio like you have done. Did you have the Ring, Pinion and Bearing polishing option added also or is that unnecessary and does the Wavetrac option require different 210mm Output flanges for the carrier. Sorry for all the questions, but I'm trying to make sure I order everything I need the first time.

Let me know if anyone needs anything REM polished. I have a guy who provides that service. At my prices...it makes sense.

I'd rather upgrade the LSD than go with different gearing. A clutch type diff makes a significant difference.

All non-stock LSD units that I know of need equal length axle stubs. You can have E46 M3 long axle stubs machined down or you can find an old 210mm diff. I'm pretty sure you can pull them from an old open diff which would be much cheaper and easier to find.

[Tbonem3]

I'd rather upgrade the LSD than go with different gearing.

x2 esp on a typical 100k+ mile diff

R&P will go forever

[Feffman]

All non-stock LSD units that I know of need equal length axle stubs. You can have E46 M3 long axle stubs machined down or you can find an old 210mm diff. I'm pretty sure you can pull them from an old open diff which would be much cheaper and easier to find.

You'll need to order one Differential Drive Output Flange (BMW part 33132229394 or 33137840564: ECS sells them for $174) if you go with a clutch style limited slip. It's the same output flange as the right side one on your stick E46 M3 differential. You'll get rid of the longer left side output flange and use two shorter right side flanges.

Feff

[Daniel]

At that price you should also be considering a drexler or OS giken LSD.

[CrisSilberGrau]

At that price you should also be considering a drexler or OS giken LSD.

I looked at the drexler website, and know of many high performance high spec cars that run their diffs. Can anyone summarize the benefits of a Drexler unit please.

[Silbergrau metallic]

At that price you should also be considering a drexler or OS giken LSD.

The OS Giken LSD is $2500 and has NO! Warranty and Wavetrac cost is $1600 and has a Lifetime Warranty on Diffsonline, The Drexler LSD is and additional $4100. Do you have any information about the Drexler and OS Giken that would justifiy the additional cost compared to Wavetrac. The Wavetrac get's pretty good reviews, so the Drexler and OS Giken units should offer a whole lot more performance for that cost, but I don't have any real world comparisons to know if it's worth it.

[lapoune]

The drexler and os giken are both high quality salisbury and the main attraction is that they are highly customizable. No real point in getting either if your not looking for something specific out of it. If you have no complaints with the M diff just keep that.

[Silbergrau metallic]

The drexler and os giken are both high quality salisbury and the main attraction is that they are highly customizable. No real point in getting either if your not looking for something specific out of it. If you have no complaints with the M diff just keep that.

I have roughly 62,000 miles on my Car and the M Diff is starting to have a Whining noise come from it and I used the very expensive BMW Diff Oil that is what's recommended and most of what I read, that Stock M Diff commonly doesn't last more than 80,000 miles. Differentials are pretty expensive to rebuild, so I'm just doing research to find the one that's the most bulletproof and gives a performance gain to boot. The longevity is primarily the reason I don't want to go back to the stock LSD.

[Obioban]

If longevity is the goal, Wavetrac is the best option. No clutches to wear out puts it in a class of 2 (the other of which can't limit slip if you lift a tire).

That was my primary deciding factor on getting the Wavetrac.

As a perk, at least on the street, it feels great (and is completely silent). In 2.5 weeks I look forward to seeing what it's like on track.

[Silbergrau metallic]

If longevity is the goal, Wavetrac is the best option. No clutches to wear out puts it in a class of 2 (the other of which can't limit slip if you lift a tire).

That was my primary deciding factor on getting the Wavetrac.

As a perk, at least on the street, it feels great (and is completely silent). In 2.5 weeks I look forward to seeing what it's like on track.

Forgive me for asking so many questions, but I'm trying to get educated. Are there two different sizes of Carriers for E46 M3 Differentials. For the stock M Diff LSD, I read something about a medium carrier with 6 bolts, but with other Aftermarket LSD there's a larger Carrier with 8 bolts and that's the reason you need to use the 210mm Output shafts.

[old///MFanatic]

I'm probably going 3.91 with the Wavetrac LSD. Thank you everyone for all the information and it is sincerely appreciated. I see your car has 4.10 gears, how significant was the acceleration gain, compared to stock, I read somewhere that some people with that Ratio start from a stop in 2nd gear, since it makes 1st so low, is that true. I tried that Gear calculator on Diffsonline, but it wasn't loading.

The gain is noticeable. Not mind blowing but the pull is noticeable. You can find plenty of youtube vids of people's before/after swap excitement.
I think it was wise you ask owners of E46 M3s like yours that have the these gears. People will have their own preference but numbers help too. As you have seen from some owners throughout thread state, first gear is useable. Now anyone can start in 2nd(even 3.62), if I had no traction that might be a nice fallback option on a slick day for a launch.
You have 19" CSL rears like me. Since you can't log in, here are some numbers. 3.62 stock will max out at 39 mph@8000 in first. 3.91 will be 36 mph, 4.10 35mph and 4.44 32 mph. Now it doesn't sound like you drive redline to redline 1st-6th, so not posting them all. What you might want to know if not a track junkie are things like cruising in 6th. So let's say you're cruising at 80 mph (with our S54 engine redline of 8,000 rpm).
with 4.44 you'll be at 3,887 rpm (22% change)

with 4.10 you'll be at 3,589 rpm (13% change)
with 3.91 you'll be at 3,423 rpm (8% change)
with 3.62 you'll be at 3,169 rpm (stock baseline)

The 4.44 should be the one to be wary of, the 3.91 and 4.10 imho aren't anywhere near that 22% change and yet peope do that too.

[old///MFanatic]

Thank you everyone for all the information and it is sincerely appreciated. I see your car has 4.10 gears, how significant was the acceleration gain, compared to stock, I read somewhere that some people with that Ratio start from a stop in 2nd gear, since it makes 1st so low, is that true.

Now if you had a lightweight track car, with a five speed lighter rotational weight drive shaft, light weight 17" wheel&tires and less weight over the rear for traction I would say then it's certainly something to consider. As mentioned, our cars already can spin them in 1st. And the torque multiplication will not help that. But I would say just like you learned with the M3 initially you modulate your pedal input. At first it'll be a change on launches, but after a while doubt you'll even remember that if you know how to drive. But there are some now and then who never adapt/like a gear change. Nothing against those in that minority. We may all have M3s but there are a lot of ways we differ in changes to how they feel (and look *Chrome M3*). Hopefully this helps some in your decision. I'm not selling 3.91 or 4.10 gears so it makes me no money if you buy or not lol.

[bigjae46]

This is me following a car that is similarly equipped. The only difference is he has a 4.10, I have a 3.62. Same OE M-Lock diff. I was chasing him this whole session. I would catch him throughout the lap but he always ran away coming out of the fast sweeper onto the oval. I think that is a great illustration of what shorter gearing does.