Differentials - 3.62 - 3.91 - 4.10

[jvit27]

I am surprised to see how most prefer a longer gearing car, shorter gearing makes the car quicker, and peppier enhances the experience, who cares about lap times, that is what got the industry in a down spiral chasing high horsepower and lightning-fast DCT's diluting the experience, why we want 6 speeds if you can't go past 3rd at full song, at that point all you need is a 4spd tranny :P . Just look at 993 Porsches gearing, it was perfect, look at 911's of today, you can only use 2 gears before asking for jail, where is the fun in that? I'd rather use 3-4 gear ratios enjoying a winding road than staying in one gear forever.

the gearbox ratios are indeed spot on, but I do feel the 3rd and 4th gears are unnecessarily long due to the final ratio.

It's a bit of a Catch-22... the S54 revs 500-1000rpm higher than most cars even by today's standards, so if you look at the actual MPH at 6800rpm it's in line with 'perfectly' geared cars. (Would be tragic to shortshift an S54 though!)
The E46 is just a heavier car which is why it doesn't spool up as quick.

Regarding lap times, just having the discussion because it was brought up-- and I don't think it's actually faster, on average (some tracks faster, some tracks slower).

^^^ this

Hypothesizing what is 'faster' on track is anecdotal. Racers will have multiple gearsets and set the car up differenly depending on the specific track. Besides, generally speaking, you don't enter a corner at 7500rpm.

This is in my view a conflicting dislike, people considering a shorter diff also tend to modify other things that make the car more feel-some, stiffer suspension, stiffer mounts, etc. A 4.1 make the car rev 10% higher at 75mph, that is only 300rpm, how can that be is so bad when probably the car is already plagued with feedback from the other mods, 300rpm on an engine that redlines at 8k are pocket change.

3.91 is +/- 300rpm higher at a given rpm.... 4.10 will be +400-500, which in effect, is roughly 1 gear higher so it's not just a matter of driving around at 7700 vs 8000.

[M3mike]

I am surprised to see how most prefer a longer gearing car, shorter gearing makes the car quicker, and peppier enhances the experience, who cares about lap times, that is what got the industry in a down spiral chasing high horsepower and lightning-fast DCT's diluting the experience, why we want 6 speeds if you can't go past 3rd at full song, at that point all you need is a 4spd tranny :P . Just look at 993 Porsches gearing, it was perfect, look at 911's of today, you can only use 2 gears before asking for jail, where is the fun in that? I'd rather use 3-4 gear ratios enjoying a winding road than staying in one gear forever.

the gearbox ratios are indeed spot on, but I do feel the 3rd and 4th gears are unnecessarily long due to the final ratio.

This is exactly my thoughts on going to a 3.91. I dont care about highway crusing rpms at 100mph in 6th gear I care about the fun I am having on twisty backroads.

[old///MFanatic]

I think 6th gear is already too short, stock, so 10% more RPMs is seriously annoying to me. And, my average cruising speed on the highway is generally 100-120 not 75...

Geez, AVERAGE 100-125mph highway! You really should open with that info.

[/M3]

While the 3.91 will have advantages on some tracks, the 4.10 will also have advantages on other tracks.

From a street driving perspective though, the 4.10 gearing will provide a acceleration bump that I believe no other N/A mod will give. It really transforms the car in that sense. Some mentioned about the 1st gear… I don’t think we spend much time in 1st gear, other than taking off.

At the end of the day there is no such thing as the best one. Each gearing will serve a different purpose for different individual. I am more than pleased with my Dinan 4.10. And being a CSL flashed SMG car makes it extra pleasing.

Now if you are a constant highway cruiser, don’t even think about changing your stock gearing. You will regret it and that’s guarantee.

[siamkazi]

Adding my 2 cents here, just got a 3.91 installed yesterday and picked up the car today. Driving away was subtle, and as I got through first and second I kind of was wondering if the stock gearing was still in. Mind you, I didn't hammer it so curious to see what 3rd gear at WOT feels like. On the freeway in 6th I didn't see any perceptible change i.e. high rpms, was easily coasting. Will update in a few days. Overall I like it, no downsides yet. Some mentioned to me that it seems more impactful on paper, I'd have to agree.

[x Spades x]

Adding my 2 cents here, just got a 3.91 installed yesterday and picked up the car today. Driving away was subtle, and as I got through first and second I kind of was wondering if the stock gearing was still in. Mind you, I didn't hammer it so curious to see what 3rd gear at WOT feels like. On the freeway in 6th I didn't see any perceptible change i.e. high rpms, was easily coasting. Will update in a few days. Overall I like it, no downsides yet. Some mentioned to me that it seems more impactful on paper, I'd have to agree.

I went from stock gears to 3.91 about 8 years ago. I ran the 3.91 for about 4 years... and there wasn't much difference from stock. It didnt feel like an upgrade AT ALL... just not much of a difference to really notice.

I went 4.10 about 2 months ago... the difference in acceleration is HUGE. I would either stay stock or go 4.10. The 3.91 will feel like stock.

[bigjae46]

I have a 3.91 which I think is the worst in between ratio. 4.10 or stay stock. 3.85 if you're looking for a cheap bump up - a decent ratio for the track.

Still, a 3.91 gives you a much better pull out of a corner assuming the tire grip is there. A 4.10 just gives you more and will not require an extra shift over the 3.91 in most cases.

[maupineda]

I went from stock gears to 3.91 about 8 years ago. I ran the 3.91 for about 4 years... and there wasn't much difference from stock. It didnt feel like an upgrade AT ALL... just not much of a difference to really notice.

I went 4.10 about 2 months ago... the difference in acceleration is HUGE. I would either stay stock or go 4.10. The 3.91 will feel like stock.

This, with 4.1 the difference is very noticeable.

[siamkazi]

I went from stock gears to 3.91 about 8 years ago. I ran the 3.91 for about 4 years... and there wasn't much difference from stock. It didnt feel like an upgrade AT ALL... just not much of a difference to really notice.

I went 4.10 about 2 months ago... the difference in acceleration is HUGE. I would either stay stock or go 4.10. The 3.91 will feel like stock.

Agreed, it's not as dramatic as i was lead to believe but I did a 3rd gear pull last night and it did pull a little harder. I guess the flip side is that as time passes I won't get annoyed. Time will tell, but i do know that i will be keeping these on.

[siamkazi]

I have a 3.91 which I think is the worst in between ratio. 4.10 or stay stock. 3.85 if you're looking for a cheap bump up - a decent ratio for the track.

Still, a 3.91 gives you a much better pull out of a corner assuming the tire grip is there. A 4.10 just gives you more and will not require an extra shift over the 3.91 in most cases.

Yeah, the 'pull' aspect is there if i romp on it which could be a plus. I find myself shifting the same so i can definitely see the value prop on the 4.10.

[elrichmeister]

[QUOTE=siamkazi;n314551]Adding my 2 cents here, just got a 3.91 installed yesterday and picked up the car today. Driving away was subtle, and as I got through first and second I kind of was wondering if the stock gearing was still in. Mind you, I didn't hammer it so curious to see what 3rd gear at WOT feels like. On the freeway in 6th I didn't see any perceptible change i.e. high rpms, was easily coasting. Will update in a few days. Overall I like it, no downsides yet. Some mentioned to me that it seems more impactful on paper, I'd have to agree.
/QUOTE]

I see that youre in Corona, which is relatively local to me. Where did you get your diff work done? Did they rebuild your original diff or did you get a rebuilt diff and swap?

[siamkazi]

[QUOTE=elrichmeister;n314660]

Adding my 2 cents here, just got a 3.91 installed yesterday and picked up the car today. Driving away was subtle, and as I got through first and second I kind of was wondering if the stock gearing was still in. Mind you, I didn't hammer it so curious to see what 3rd gear at WOT feels like. On the freeway in 6th I didn't see any perceptible change i.e. high rpms, was easily coasting. Will update in a few days. Overall I like it, no downsides yet. Some mentioned to me that it seems more impactful on paper, I'd have to agree.
/QUOTE]

I see that youre in Corona, which is relatively local to me. Where did you get your diff work done? Did they rebuild your original diff or did you get a rebuilt diff and swap?

Called Unitrax, they're off Serfas Club, did a great job. I just gave them the ring, pinion, and seals etc and they swapped it out and rebuilt the diff. It's around $650 if you take the diff to them, another $350 if they take the diff on and off the car (what I did). I did a night drop-off i.e. left the keys in the door via a lock. Service is good and the work itself I'm happy with, they get the details down. Eddie is the head differential guy. Fyi I'm not affiliated in any way etc.

[Advorsor]

I have a brand new 4.10 ring and pinion that I don't plan on using. Does anyone have a 3.85 ring and pinion, specifically, that they would want to trade straight up?

[lcrain]

So many opinions on this. I really like short gears on high revving, manual cars. Going to 4.10 on my old e46 m3 was perfect, for me. The acceleration felt much more brutal and I was engaging with the transmission more. Did not bother me at all on the highway (granted I usually don't cruise above 80). My e36/s54 racecar has the stock zf 5 speed and a 3.91 which I believe to be quite comparable to a 6 speed e46 with a 4.10 rear end for the first five gears. It is perfect on the tracks I go to. I never have to use 2nd gear. There are a few corners where I wish I had more revs in 4th or 3rd to avoid a shift but it is rare and the gains elsewhere are worth it. I have never been to a track where my detuned s54 ( just under 300 whp for class) has needed more revs in 5th, ever.

I understand there are tradeoffs and everyone has their own opinion but I found the 4.1 really increased engagement and fun in my e46 street car.

[maupineda]

I have the 4.1 and it does transform the car, I drove an M3 with regular gears and it feels anemic by comparison.