Quote:
Originally Posted by drunkenup
spxxx probably has the hardest driven AT track 1er and is the guy to ask i would think
The ATF exchanges heat with the radiator, this helps it heat up quicker in cold climates but then if the coolant is getting hot, so is the ATF (which can't get too far above 200f, that'll break down ATF quickly). At the same time, ATF heat burdens the engine cooling circuit.
For you SoCal folks separating the two circuits and giving the trans its own cooler works well it seems, but then does it warm up well in cold climates? I haven't found the answer. I want to do a 335i dual duty car but its 30 degrees here, soon to be high teens.
AT has a nice gear spread from 3-5 and 6th is an actual overdrive (manual ratios suck), esp. third gear being shorter which is where you'll be in most of the time
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Honestly the ZF 6HP has been solid for ~3yrs with a 19 row tranny cooler core and full removal of the heat exchanger. I've mounted the ATF cooler behind the grills which leaves room for dual oil coolers. As others have said, the AT cars will run hotter and the tranny will shift slower once heat rises but I can get 30+ minutes out of it in essentially any temperature.
If you look at the M235iR, it runs the ZF 8spd which is quite similar and those run in many endurance series.
I'd just go out there stock and log every parameter (MHD will log water, tranny & oil temps) then determine where you need to upgrade. Should be fine in Winter and if you're not pushing it hard... my car didn't run a tranny cooler for 1.5yrs when I was just dipping my toe in HPDE without temp issues.