BMW diff?
 

Can anyone tell me which differential is the best for my 733i 1977? I want
the best acceleration, consumption and top speed are not important.
Thanks

You don't want to know which diff is best, you want to know what gear ratio
is the best.

Higher numbers will give greater accelleration, but lower top end. For
example, the stock ratio is going to something in the range or 3.45:1,
4.10:1 will give better acceleration, 4.56:1 will be even better, but the
top speed will suffer because the engine will top out earlier.

A car turning 3.45 gears will go faster than a car spinning 4.56s, but it
will not be as quick. You seem to be interested in quickness at the expense
of top end, which is why I went off on this particular tangent. That is,
assuming you have enough horsepower to allow the engine to reach peak RPMs
in the highest gear, the speed at that point will be greater with taller
gears (lower numeric value) in the differential than with lower gears
(higher numeric value).

I used these numbers ONLY to illustrate the point, I have no clue as to the
availability of them for a 7 Series car, the acutal ratio you get will
depend on physical size factors of the differential housing itself.




"LPG systems" > wrote in message
...
> Can anyone tell me which differential is the best for my 733i 1977? I want
> the best acceleration, consumption and top speed are not important.
> Thanks
>
>

Here's a place to go shopping: http://www.koalamotorsport.com/

While it's nice to improve the acceleration of your car, a higher ratio
differential will make it's presence known most often with higher engine RPM
at cruising speeds. It might not be particularly rewarding to cruise the
freeway at 4000 RPM.

R / John

"LPG systems" > wrote in message
...
> Can anyone tell me which differential is the best for my 733i 1977? I want
> the best acceleration, consumption and top speed are not important.
> Thanks
>
>

"John Carrier" > wrote in message
...
> Here's a place to go shopping: http://www.koalamotorsport.com/
>
> While it's nice to improve the acceleration of your car, a higher ratio
> differential will make it's presence known most often with higher engine
RPM
> at cruising speeds. It might not be particularly rewarding to cruise the
> freeway at 4000 RPM.
>
> R / John
>
> "LPG systems" > wrote in message
> ...
> > Can anyone tell me which differential is the best for my 733i 1977? I
want
> > the best acceleration, consumption and top speed are not important.
> > Thanks

Same ethics as me with my 525e ... i wanted the best acceleration ...
consumption and top speed were irrelevant.
Its now got a 3.91:1 diff under its belly.
Its got a rapid pull away, yet still reaches 130mph on the speedo (more like
125mph in real life).

As for fuel consumption ... around town its unchanged!!
Basically, where it used to use 2rd gear at 25mph, it now uses 3rd ....
where it used to use 3rd at 40mph it now uses overdrive ... so below
40mph, the revs vs speed are the same!!!
Its a bit thirstier on a run above 70mph/3000rpm though.

If you can, fit a 4.1:1 diff from a 2 litre e34 (if they are the same ... or
maybe
swap the internals).




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"Jeff Strickland" > wrote in message
...
> You don't want to know which diff is best, you want to know what gear
ratio
> is the best.
>
> Higher numbers will give greater accelleration, but lower top end. For
> example, the stock ratio is going to something in the range or 3.45:1,
> 4.10:1 will give better acceleration, 4.56:1 will be even better, but the
> top speed will suffer because the engine will top out earlier.
>
> A car turning 3.45 gears will go faster than a car spinning 4.56s, but it
> will not be as quick. You seem to be interested in quickness at the
expense
> of top end, which is why I went off on this particular tangent. That is,
> assuming you have enough horsepower to allow the engine to reach peak RPMs
> in the highest gear, the speed at that point will be greater with taller
> gears (lower numeric value) in the differential than with lower gears
> (higher numeric value).
>
> I used these numbers ONLY to illustrate the point, I have no clue as to
the
> availability of them for a 7 Series car, the acutal ratio you get will
> depend on physical size factors of the differential housing itself.
>
>


Now I have 5 speed gearbox from 735i and a 3.45:1 diff from 733i and I
noticed that my car has a slower acceleration now than with 4 speed gearbox.
I had in plan to switch back 4 speed gearbox and to put 3.91:1 or 4.10:1
diff.
I am preparing this car for street racing in Croatia but I have some
problems with finding some parts.
I wanted to buy E24 (6 series) bmw but there is no a single car in Croatia
which is in a good shape. But then I found this one which is remarcable and
I turned it into a drag race car. Actually I'm still doing it but I plan to
finish it in next few months.
Do you know which BMW's have stock sperr diffs with that ratio?
Thanks for any help