Barry, I beg to differ but its not quite that simple. The 3.45 has about 9% more torque than the stock 3.15 dif. The top speed of the 3.15 won't be that much if any higher though BECAUSE the M5 will not pull to redline with the stock dif, but it should with the 3.45.
With stock gearing the M5 would go 197.6 mph at the stock redline of 7000 rpm, BUT the stock engine can't come close to pulling that speed (maybe 12 mph less than that as a guess, say 185.6 mph)
Since the Dinan software and others that remove the top speed limiter also raise the RPM limiter, lets use 7200 rpm as the redline. In my opinion the Dinan software is the best (also the cheapest) first mod for an M5 and I highly reccomend it to everyone. I do have the 3.45 dif and I just assume that everyone with a 3.45 has the software too.
So, the M5 with the stock 3.15 gearing and the software would go 203.2 mph at 7200 rpm IF the engine could pull it to that speed, but in reality it still tops out at the same 185.6 mph (aprox.) in 6th and the exta revs can't ever be attained.
However, the M5 with the 3.45 gearing will only go 185.6 mph at 7200 rpm, but Dinan says the engine will actually pull that speed in 6th.
So IF you believe the above numbers, the 3.45 will have the same top speed as the 3.15 and it will get there sooner. At most the 3.15 could have a 1% or 2 % higher top speed, never 10%.
By the way, I have never gone 180 mph and I don't plan to, but its nice to know I could.
with 3.15 gearing (Iam assuming this for the euro model) max speed was 172 mph using 6th @5700 rpms, time 149 seconds.
with 3.45 gears max speed was 172 mph using 6th @6300 rpms, time 139 seconds.
Some driver notes
Speedometer is highly inaccurate at speeds above 150mph.
Vehicle was extremely stabel at max velocity.
No matter the gearing terminal velocity is172 , It just how fast do you want to get there.
Excellent job of explaining this tough subject. Gearing and top speed always arouses some serious debate on this board.
By the way, I recently took the BEAST up to 150 on a deserted stretch of I-10 between Houston and San Antonio (no other cars around, no entrance/exits, and I could see very far away) and boy did it reach a buck-fifty quick!!!! Whew!! Pulling like a freight train all the way up till I pulled back on the throttle.
and for those of you who don't know, I also have the Dinan software, CAI, and the 3.45 diff on my car. It pulls noticably stronger in every gear.
Just once though, I would love to take it to an oval track and run all the way to top speed?!!!!
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Andy
'00 Imola Red M5 - sold 4/02
'00 Mustang Cobra R - #155 of 300
'02 F-250 SD Powerstroke Crew Cab 4X4
'00 Honda Accord V6
Multiple tests in Europe show the terminal velocity to be around 184 or so, not 172. If there is any question about it, I'm sure Johan can clarify it because he knows first hand.
If you have a raised speed limiter a 3.45 car and stock car will have virtually the same top speed on level ground. However the stock car can reach higher speeds going downhil.
If you add more power to the car and still have 7200rpm as rev limiter the stock car will be faster.
A car with the stock 3.15 would hit rev limiter in a speed that is 9% higher than a 3.45 car ONLY if it has power to reach that speed. The stock car certainly hasn't nor have mine.
The stock car can reach 296km/h (185mph) on level ground and perhaps up to 310km/h going downhill. I've reached more than 305km/h true speed on level ground and above 310km/h going downhill with my slightly modified M5. I also managed to reach above 310km/h when my car was stock (except from VMAX limiter removal) going downhill.
I really like your reasoning, but it is not correct. Dinan and anyone else will tell you when you go to a taller final drive that it will reduce the top speed and it certainly is my experience with other BMWs which I have modified. However, the loss in top speed is more than offset by the increased torque at lower speeds. I suppose that your theory would work if you could increase redline to some number (probably considerably higher than 7200) where the top speed is the same, but in general, the top end is going to be reduced.
Originally, I called Dinan dealer that I would like to check out the price for 3.45. But, they told me I better save the money for the kit (including header, fuel injectors, software, intake, exhuast).
As they told me, the kit will push the beast up to 470hp?!
And, it probably will be availble in March.
Anyone heard the same story???
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Dinan: Stg 3 Software, CAI with all updates, Flow meters, exhaust, 3.45 diff, Stg 3 Suspension, Front Strut Brace, Rear Shock Brace, Wheels (Tires: Front 265/Rear 275), Floor mats
Others: AC Schnitzer Front Spoiler, AC Schnitzer Foot Pedals, 6000K, Brake Ducts, M Audio woofers, UUC Flywheel+Clutch, UUC EVO3 SSK
3.45 top speed?!
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