3er, 5er and 7er auto tranny info

[andrew.j.thomas@xxxxxx]

Dear all.

Som info reported in 'Autocar', 25 August 1998, which may be of interest to
those of you considering an autobox in your new 3 or 5:

BMW just announced a new 5er diesel called the 530d - a 3 litre blown V8
with 184 bhp and 288 lb-ft of torque at most engine speeds (the car is
extremely fast - faster as an auto than the 528i, but that's another
matter). Also it has released a 730d with the same engine and rated bhp but
with slightly higher boost - 2.5 bar vs. 2.2 bar, allowing it to make 302
lb-ft of torque at most engine speeds, to compensate for the 7er's higher
kerb weight.

Now, the 7er uses the ZF 5HP-24 auto tranny used in all the other 7s, but
the 5er, despite having the same engine, will have the new GM 5L40-E
5-speed auto transmission as an option. Why? Well, the GM tranny has a
maximum torque rating of 290 lb-ft, making it unsuitable for the 7er
application. Also GM's new 5-speed auto will be produced (in Strasbourg,
just like the current four-speeders) in much larger numbers, and therefore
will be cheaper, an important consideration when you take into account the
numbers of 5er diesels BMW sells in Europe. Moreover the GM tranny is 15 kg
lighter than the ZF 5HP-24, and lightness of weight is another important
consideration for the 5er.

BMW has apparently ordered 150,000 of these 5-speed auto transmissions,
obviously not all for the 530d; it will eventually filter into the rest of
the 5er range and 3er range destined for the US and Japan. When this will
end up in the US-market 5er petrol models wasn't indicated, but it must be
pretty soon (should also appear in the auto Z3 2.8 as well, if the 5-speed
is to replace the 4-speed wholesale).

Whether this means other Euro 3s and 5s get the new 5-speed GM transmission
I don't know - it wasn't implied, and six-cylinder Euro E46s are currently
fitted with the ZH 5HP-18 'box. Seems odd, when the two 'boxes are so
evenly matched in low-torque (i.e. below 290 lb-ft) applications. In my
experience, GM units tend to slur upwards shifts more than ZFs, and are
more relaxed in their kickdown response - but surely this is something that
could be emulated in software rather than hardware?

By all means send me an email if you want more info - Autocar did go on
about it in fair detail.

Cheers

Andrew T
'95 318is.

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