Probably the best bang for the buck mod available for the M5. Yes, the car gets faster acceleration, but the top speed is tamed a tad. As a side note, it will make first gear shorter, and raise the revs when cruising at speed.
Short diffs do make a difference to acceleration, but I would guess that 1st becomes a little too short and cruising feels somewhere between 5th and 6th, which would bother me less.
I did have a look at the ratios of the 6 speed box, for me in a perfect world I would shorten 6th a little and lengthen 1st a little and reduce the revs drop between the gears. Ie fit a new set of gear ratios (very, very expensive)
You can do the maths and look at the area under a torque / gear ratio plot and review the torque at the rear wheels at say 0-150 mph and see how this fits and the improvement over a standard rear diff ratio. I have a program somewhere that does this for me, I'll try and dig it out !
I did have a look at the ratios of the 6 speed box, for me in a perfect world I would shorten 6th a little and lengthen 1st a little and reduce the revs drop between the gears. Ie fit a new set of gear ratios (very, very expensive)
If you want to play these games, you need to buy a car with a different brand transmission....maybe a T56. These E39 6spd transmissions are not serviceable by anyone except Getrag themselves as they do not offer service replacement parts to anyone, not even race teams, BMW or Getrag transmission jobbers/distributors. Getrag truck transmission jobbers can not get these parts either. The only thing available is a refurbished transmission....not even a new one....and you can be sure it contains a bunch of used and abused componentry with x# of miles on it. A detent bushing will cost you $4500. A new cluster gear will cost $4500. A new synchro will cost $4500. A new case-to-tailhousing gasket will cost you $4500. This is a real lucrative business for the Getrag Factory Service Group and they have no intention of releasing parts. I am frankly amazed that amateurs competitively race the E46 M3 (Getrag) under these repair constraints. GM and Ford teams running T56 or similar transmissions can buy ANY part for pocket change.
->Alternate Getrag gear ratios are not available at any price<-.
I'm sure you get the idea. Drive carefully.
Last edited by Lscman; 23rd September 2004 at 11:54.
Probably the best bang for the buck mod available for the M5. Yes, the car gets faster acceleration, but the top speed is tamed a tad. As a side note, it will make first gear shorter, and raise the revs when cruising at speed.
Travis
Exactly how much faster is the car in the 1/4 mi? The car will accelerate harder at the same RPM with 3.45 gears and this sensation WILL be felt. What you may not notice is you're going slower (at the same RPM). At the same SPEED, you may or may not be accelerating harder. There are many threads on this subject.
i dont like the idea of having to buy someone else's core and paying for it!
Dinan is not the only game in town as their offerings are very limited. There are several retailers for M5 differentials including Evosport. In fact, there are M5 differentials being marketed in multiple gear ratios with flexible static and dynamic posi bias options.
Last edited by Lscman; 23rd September 2004 at 11:58.
If you want to play these games, you need to buy a car with a different brand transmission....maybe a T56. These E39 6spd transmissions are not serviceable by anyone except Getrag themselves as they do not offer service replacement parts to anyone, not even race teams, BMW or Getrag transmission jobbers/distributors. Getrag truck transmission jobbers can not get these parts either. The only thing available is a refurbished transmission....not even a new one....and you can be sure it contains a bunch of used and abused componentry with x# of miles on it. A detent bushing will cost you $4500. A new cluster gear will cost $4500. A new synchro will cost $4500. A new case-to-tailhousing gasket will cost you $4500. This is a real lucrative business for the Getrag Factory Service Group and they have no intention of releasing parts. I am frankly amazed that amateurs competitively race the E46 M3 (Getrag) under these repair constraints. GM and Ford teams running T56 or similar transmissions can buy ANY part for pocket change.
->Alternate Getrag gear ratios are not available at any price<-.
Dinan is not the only game in town as their offerings are very limited. There are several retailers for M5 differentials including Evosport. In fact, there are M5 differentials being marketed in multiple gear ratios with flexible static and dynamic posi bias options.
RDSport has released their new M5 limited slip differential, and a core exchange is not required. Here is some product information:
The new RDSport AI-LSD for the M5 detects the slippage of your rear tires and adjusts the locking ratio from 10% to 90% as needed. This new technology is employed on all BMW race cars and has proven to be the most effective way to deliver massive power to the rear wheels without absorbing unnecessary power through fixed ratio locking mechanisms.
The RDSport AI-LSD is not a Torsen/Quaife type gear-based LSD, but a fully variably adjustable clutch based unit. It is sold in 2 different configurations:
A standalone unit to be fitted in the customers differential housing.
A complete replacement differential housing with your choice of final drive ratios.
For more information and pricing, please contact BeastPower.
I've had the Dinan 3.45 installed for 20K miles - expensive upgrade, but you will feel the difference around town and on the highway too. IMO, it's not too steep of a gear at all.
Lots of threads on this!
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