Originally Posted By: Claud
What is the ideal operating temperature range for an automatic transmission?. In particular for the transmissions on my '87 Olds 88 and '89 Buick LeSabre.
I live in the Uk so get nothing like the ambient temperature swings like a lot of North America. 25f-95f is about as much as it gets for me.
I have put tube and fin coolers on them as I haul a 1700lb trailerhome with them, this on the advice of my local highly reputable transmission guy.
I know an overheating transmission will fail very quickly, but how much damage will running cold do?.
Incidentally, I have been told that the cooler lines only have much flow when the converter is locked. This seems illogical to me, surely most heat is generated when the converter is slipping?.
Any gurus here willing to enlighten me please?.
Claud.
I can't answer this directly, but just from my experience with my van and trailer. One of my first vehicle upgrades to the van after getting the trailer was to install a transmission temperature gauge. The point at which I had the temperature sender mounted was in the transmission line, just as it came out of the transmission, and before the vehicle's radiator (which supposedly had an upgraded radiator with an integrated cooler for towing). I chose this location as I figure it should be the fluid at its hottest point in the system, and will therefore be a good early warning for high temperatures. The vehicle is a 2006 Toyota Sienna, FWD, Aisin 5 speed auto.
When NOT towing, here were my observations on temperature:
Ambient temperature, vehicle speed and whether the air conditioner was on or not were the three primary factors in the running temperature of the transmission:
- Ambient temperature around 70F, no air conditioner: with stop and go driving, about 190F, in town not stop and go, about 160 to 170, and highway as low as 130F.
- Ambient temperature around 90F with the air conditioner: stop and go around 215F, in town not stop and go, about 180F, and highway between 140 to 150F.
- Ambient temperature around -5F, possibly air conditioner kicking in and out for windshield defog mode: stop and go driving, may be lucky to touch 110F, in town not stop and go, maybe 90F, and highway maybe 60F if lucky.
Towing has the effect of greatly increasing most of these temperatures, especially under extreme conditions: mountains, high ambient temperature and A/C, I've had times where I near 240F, before I make a decision to pull over and let it cool down before proceeding. It would have certainly continued to climb had I not stopped.
I added an external passive transmission cooler shortly after, and under all conditions, it has lowered temperatures, from significantly (while in motion), to minimally (stationary or very low speed).
So, my transmission going through all that, including not getting warm in the winter has held up just fine and is showing no signs of deterioration, other than maybe minor "looseness" which could be attributed to it's age. It is 9 years old, with over 130,000 miles, and has seem summer towing duty since about the 3 year old / 40,000 mile mark. It has always seen an annual drain and fill since it entered towing duty.
That said, I have also heard of some auto trannies not being fond of the cold, like some on certain Mitsubishi models.