I was wondering how many people in the northwest have rear diff upgrades. I'm thinking of putting a open 3.46 diff in my 2001 325I. so I thought I would see anyone has this upgrade.
also My dad is thinking of a 3.23 lsd out of a E36 m3 he has a 1998 328I.
let me know what you guys think.

i have a difs online diff 3.73 40% lockup..i love it. the only reason why i keep up with M's!

Can somebody explain to me (unaware of Advantages/Disadvantages) the differences between the options for "upgraded" diffs? Is there some for the M3 too?

edit* Actually, I'll just do a search :).

Can somebody explain to me (unaware of Advantages/Disadvantages) the differences between the options for "upgraded" diffs? Is there some for the M3 too?

edit* Actually, I'll just do a search :).

Not sure I understand your question. I have a Diffsonline 3.64. Great performance upgrade.

Jay

Oh, I was just curious as to why some people got different diffs.

I'll save you some time. Two reasons why. Either they want LSD or more lock up than their current diff offers, or they want shorter gearing for faster acceleration.

Too much lock up is not a good thing necessarily so don't think you need 70% lock up. Also, though you may get quicker acceleration, you will loose top speed. That may not seem like a big deal, but if this is a street car, you have to consider how your freeway speed cruising rpm's will change. Going from a 3.15 like I have, or a 3.23 like you have Steve, to a 3.73 will really raise your rpm's when traveling at 60 mph. Also, think about how much less time you will spend time in each gear if you were to go really short. There comes a point when you aren't able to fully take advantage of your motor (granted, it's a bit up there)

In my case, I wouldn't mind going a little shorter at some point. But, I could care less about rpm's at freeway speeds since pretty much the only time I am at those speeds consitantly is on the way to the track. But, I may gain as much as 5 mph on the straights if I could accelerate a little quicker so the benefit would be worth it to me.

Gotcha, so a track dedicated car might see more advantage from a 3.73 diff.

No, a street car would too. I'm just saying that you need to weigh the pro's and cons of it.

Going to a lower rear gearset is probably the biggest performance bang for the buck with our cars. It benefits acceleration in all gears. A small change may not very noticeable and too big a change may not be good either.

There are downsides. A loss of top speed (not many of us explore the area north of 135mph). A loss of gas mileage when doing freeway or open highway driving. With a stock 3.23 diff I'm at ~2750 @ 65mph. With my 3.64 diff I'm at ~3250 at the same speed. It's less of a problem on surface streets. I'm just using the next higher gear. So, instead of driving around in 3rd gear @ 40mph, I'm in 4th.

The benefits on the track are good for a BIG smile.

Jay

Going to a lower rear gearset is probably the biggest performance bang for the buck with our cars. It benefits acceleration in all gears. A small change may not very noticeable and too big a change may not be good either.

There are downsides. A loss of top speed (not many of us explore the area north of 135mph). A loss of gas mileage when doing freeway or open highway driving. With a stock 3.23 diff I'm at ~2750 @ 65mph. With my 3.64 diff I'm at ~3250 at the same speed. It's less of a problem on surface streets. I'm just using the next higher gear. So, instead of driving around in 3rd gear @ 40mph, I'm in 4th.

The benefits on the track are good for a BIG smile.

Jay
well put! just what i was about to say.

so if I do get the 3.46 I will increase the performance without to much of a loss of MPG and top end. cool thats what I thought.

think I should talk my dad into getting the 3.23 lsd rear diff out of a M3

your dad should get a 3.38 out of an auto obd2 m3.

I was wondering how many people in the northwest have rear diff upgrades. I'm thinking of putting a open 3.46 diff in my 2001 325I. so I thought I would see anyone has this upgrade.
also My dad is thinking of a 3.23 lsd out of a E36 m3 he has a 1998 328I.
let me know what you guys think.

i put a 3.23 I'm my 328 about 4 months ago. best mod i have done. it did raise my rpms a bit, but the added traction in the rain is more than worth it, and the acceleration is a bonus

bfowler if you dont mind me asking about how high are your Rpms at 60 mph?

bfowler if you dont mind me asking about how high are your Rpms at 60 mph?

Go to www.diffsonline.com

Under the tech section you'll find an rpm/mph calculator. Just plug in the values and you'll get your answer. Very cool tool.

Jay

I really enjoy my 3.25 lsd, matches the zf tranny/m52 combo very nicely.

bfowler if you dont mind me asking about how high are your Rpms at 60 mph?


i will go for a drive at lunch time and turn on the digital tacho diagnostic and let you know:cool

bfowler if you dont mind me asking about how high are your Rpms at 60 mph?


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