Which is better 4.10 or 3.73 LSD?

[Curtis325is]

I just installed a 4.10LSD a few weeks ago in my 325is.

I love it. The car is so much more fun to drive. I think i get better gas mileage around town, probably because it takes less effort to accelerate (ie don't have to push as hard on the gas to get moving).

It revs higher on the highway. The extra engine speed/sound would only start to get annoying if you drive at 90mph all the time. 70-75mph is perfectly fine to me. I don't really notice any difference in highway gas mileage. Infact it accelerates up hills more effortlessly which probably uses less gas.

The only reason i would not do this mod is if I did more then 50% of my driving on the highway at higher then 75mph for more then 30mins at a time.

[rcfanatic]

I'm also debating the 3.73 vs 4.10.

So traveling 80mph, it looks like the 3.73 revs to 3400 and the 4.10 to 3700. Does this 300 rpm difference really bother people that much? At 80mph, wind noise seems like it would drown out any increase in engine noise.

[nando]

I never drive at 80mph. There's no reason for me to cruise at that speed.

[rcfanatic]

Anybody else have input on this 300 rpm difference? I don't see what all the hoopla is about

[nando]

the noise of my tires would vastly drown out any increase in engine noise. and the engine doesn't really start getting loud until about 4k.

[freakazoiid-E30]

This post made my sun shine lol

[gearheadE30]

Do any of you really cruise at 80? Cut off 10-15 mph and you'll see more economy gains than a diff will likely get you.

If it makes any difference at all, I'm going to be putting a 3.73 LSD in my 318is turbo. The lower highway rpm will be nice, but really I'm doing it because first and second gears are completely useless in average driving.

[rcfanatic]

I always cruise at 80 for multiple reasons.

1. You get to your destination faster
2. The right lane is too slow and has too much traffic getting on/off the highway
3. The speed of the middle lane(s) is/are too inconsistent and it's more dangerous because more people are changing in/out of it/them.

Left lane at 80+ mph is the easy answer for me. Might cost you more but it's not without its benefits.

And I agree, the stock 4.10 with a 318 turbo is too high

[a3ternus]

Just get a 4.10 definitely.Best all around ration for a stock 3.25i.
N.

[dashboardmonkey]

The S4.10 is tons of fun around town, not so much on the freeway (80mph=4000 rpm) but it's lots of fun to hit second gear hard and get her a little squirrly. Mt highway mileage was 28mpg on the way to the E30 picnic earlier this year, but I only get like 18 around town. Not sure on exact mileage numbers around town but the gas seems to go alot quicker around town.

[priapism]

Do any of you really cruise at 80? Cut off 10-15 mph and you'll see more economy gains than a diff will likely get you.

I usually cruise at 85, if traffic allows it. On open patches of desert I'll go 99 for long stretches. Once in Mexico I cruised at my truck's top speed for 140 miles

This isn't in my e30. The 4.10 sings on the freeway. 4500rpm gets old quick. And yes, a 4.10 will lower your top speed as it will run out of revs before it runs out of steam. I'm hunting for a 3.73.

[gearheadE30]

haha okay, well I live in Indy, where there are no deserts to speak of, and the highest speed limit is 65...

[gverelli]

I have read many people saying the 4.10 is amazing for the m20 and it really "wakes" it up, although I had never driven with a 4.10. That being said, I took a ride as a passenger in my instructors 325 touring, and he later on told me he had a 4.10, I was completely shocked because I did not feel any difference at all (in acceleration), he told me it was the best thing he had ever done and worth the sacrifice on the highway. Im guessing you really need to be driving it to feel the difference. I have been looking for one locally for a while with no luck, so until then I can't really say much more on how it feels.

Edit: in all honesty though, the 3.73 feels great, if everyone says it is THAT much of a difference, then hell I can imagine how fun it actually would be to put a 4.10!!

[rcfanatic]

I could see it not feeling like that big of a difference as passenger. Especially since the stock ratio is 3.73.

However, my stock ratio is 2.93, so the 4.10 is going to be silly.

Oh, and in Florida the speed limit is 70, so 80 is a comfortable 10 over. In Miami there practically is no speed limit, and the lines are only suggestions lol

[nando]

is 80mph really 4000rpm? I don't think it is.. 75 is just over 3500rpm. But my tires are a little oversized.