Quote:
Originally Posted by Ghost-Flame
Is there an advantage to having an auxiliary trans cooler on these transmissions even towing a trailer or a boat?
I tow a trailer with my Motorcycle with my 3.0 e53. The trailer and Bike weighs about 1200 lbs. I generally do high way trips but, I go as fast as I can... 70 to 85... 90  depending on the State. I always wonder if I am abusing the trans and have thought about getting a trans cooler. Based on these 2 above posts It sounds like the transmission has plenty of cooling ability and cooling it further may be detrimental, am I correct? |
Well, this is just my opinion, because I don't have hard data to back it up. That said, my observations jibe with it. I don't think you are doing any damage to your transmission at those loads. And speed doesn't equate to transmission load. Steady state on the highway, if the torque converter is in lock up mode, isn't putting any significant heat into the transmission.
Quote:
Originally Posted by Ghost-Flame
Are modern transmissions better at cooling than the old automatics? My uncle burned up a transmission on a brand new 1970ish, loaded, ford LTD station wagon, pulling a pop up camper, when they replaced the transmission they put an auxiliary cooler on it and it lasted for years after that.
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Yes, much better. I used to install transmission coolers on vehicles like that (we even had a succession of LTD wagons at home, up to the 460 cid, and used for towing). If those vehicles were towing much, we also put in shift kits, usually a different check valve and spring in one of the passages in the valve body, to firm up the shifts and reduce clutch slippage.
Older automatic transmissions were great sources of heat, and consequently burnt the transmission fluid fairly easily. That is where the whole fluid change process that is debated here came from. Modern transmissions convert more of your engine power to forward motion, in a quest for fuel economy, so there is much less waste heat generated. Less heat means the transmission fluid lasts much longer. Part of it is the transmission shift strategy (backing off the timing during a shift using the ECU, to reduce power and reduce clutch slippage) You can tell that one works, since clutch plates come out of high mileage BMW transmissions looking like new (as reported many times on the rebuild posts) and old 1970 era clutch plates came out cooked. An even more important element is the lock up torque converter. A slipping torque converter generates heat, and all older ones thus generated a lot of heat. A locked up converter (and BMW uses an aggressive lock-up strategy) doesn't produce any heat, as there is no relative motion to churn the fluid.
As a side note, that is what is most important when you are pulling a trailer, that you keep the transmission in lock-up. You can tell when it locks or not (revs change) and as long as it is locked up you are being very easy on your transmission, no matter what load or speed you are at. Too much load and you will have to drop a gear to keep it locked up, but that is better than trying to pull a higher gear and generating heat.
Jeff