The down side of the 3.46 differential

Quad_exhaust · 28th July 2001, 03:45

Hi all,

I've been running the car quite a bit lately on 0-60 runs, and now that I have the 3.46 differential, I'm bothered by one factor - I have to shift from 2nd - 3rd before I hit 60mph! I called the tuner, who mentioned the gearing isn't a direct bi-product of the cars hp or torque, so "adding a few hp" won't cure this.

Anyone else experience this - having to shift before hitting 60? If somebody with the 3.45/6 differential could reply with their ratio, along with what max mph speed they get prior to shifting from gear-to-gear, that'd be terrific. Mine looks as follows:

1st gear up to roughly 28mph
2nd gear up to 56mph
3rd gear up to 75-78mph
4th gear up to 98-102mph
5th gear up to 125mph+ ...give or take a couple on each...
6th...don't know the limit yet!
Quad

AndyMenard · 28th July 2001, 04:40

Quad,

Are you really surprised? I'm not. It is a foregone conclusion that the lower gears will require a shift to 3rd before reaching 60.

Although I have not yet done the new gears (I am eagerly waiting for it to arrive!), I do still plan on doing it despite this drawback.

Here is the way I see it... I don't do any street "light to light" racing, so I don't much care if I have to shift to 3rd before reaching 60... What I DO care about is feeling the extra torque at the back wheels using the "Butt-O-Meter"!!

Bottom line... who cares if the car does 0-60 in 4.7 or 5.0 (or whatever?) .... the BEAST is plenty fast ... fast enough to hang with many a great sports car.. and this puts a grin on my face!

I don't get too caught up in all of the marketing numbers... after all, not many of us (myself included) can actually make the car go that fast in that time period. This is just a fact of life. Not to mention - I would be worried about premature wear and possible destruction of the clutch under several hard launches.

Just my 2 cents!

DavidB · 28th July 2001, 04:50

Does your car have a modified chip?

stever · 29th July 2001, 00:11

The Dinan chip adds 300 rpm so you can get to 60 before the shift. I've never timed 0-60 but the extra little bit before hitting the limiter is welcome with and without the 3.45.

rtorre · 29th July 2001, 04:23

Quote:

Originally posted by Quad_exhaust

5th gear up to 125mph+ ...give or take a couple on each...
Quad

Many sport cars (Mustangs, NSXs, C4s, C5s, ect.), although able to reach 150mph, take a much longer time than the M5 to go from say, 110 to 150mph.
I´ve encountered many of this cars doing around 110 and engaging in a lets-see-who´s-boss game. All I can tell it´s that 5th gear having its greatest use in the 110-145mph range, has always given me the "boss" certificate.

I doubt I could do this if I had to use 6th gear in that range.

Like I said before, I still have to see an M5 with a 3.45 rear end bit the stock Standing Km = 24.1sec or the 0-150mph = 30sec

As for the kick-in-the-buttometer-gauge, I have my Go-Kart, thank you.

Ricardo

Tim W · 29th July 2001, 05:00

On my 540i I went ffrom a 2.82 to a 3.15 and it shortened up the run of the gears but how often are you stretching the legs of 6th gear anyway?

The get up and go at the low end makes for mor fun!

Tim

PaulMarin · 29th July 2001, 08:21

With 3.45 and Dinan chip 2nd gear goes to 60.9 mph, 5th gear to 154mph. The 3.45 is cool.

panoply · 29th July 2001, 08:48

My very first impression of the M5 was that the gearing was unnecessarily short. When truly driving relaxed, it's natural to skip gears. I suppose they were trying to assure a good 0-62 kph time. The car is so nicely torquey, it's just not neccessary, in my view.

DavidB · 29th July 2001, 15:06

Dave,

I totally agree that the M5 is well geared and the 3.45 diff is not necessary, but for anyone who is hoping to reduce their acceleration numbers, this may be the best option. Once someone posts some stock vs 3.45 data, the decision will be easier for people to make.

MarkM5Lauderdale · 29th July 2001, 16:36

Found the 3:45 on the track to be very helpful. Road course work means fewer shifts. Found the same to be true on the street. Downtown I'm usually using gears 2-3 for heavy traffic. 1st is unneccessary unless scaring the local kids!
Acceleration to 60 is very good with Dinan's added 300rpm. I do find myself "red-lining" more often with the new differential but I'm learning to back off. May even get me to slow down some. Been pushing my luck with speeds.