Transmission Temperature

[Cougar]

I have questions about transmission temperature.
We were riding around the countryside yesterday at 35-45 mph. with no hauling or towing load. The outside temperature was in the low 90's. My transmission temperature display showed a high temp of 191 degrees. I have never seen it this high before. Is this a normal reading?

[carco]

For my 04 LLY yes, not that unusual before an additional trans oil cooler under truck.

[More Power]

191 is not a problem. You'll see higher than average trans temps whenever you're driving in hot conditions at speeds below where the transmission torque converter locks. Using Tow/Haul, which locks the TC in 2nd and above, can help to reduce trans temps, but 191 isn't a problem....

Jim

[Cougar]

Thanks, guys. I guess the DIC is giving me more info than I can digest. Seems to me the owners manual should explain what the normal parameters should be. Thanks again.

[kaylabryn]

General rule of thumb is 100deg over ambient.

Mike

[rat4go]

In addition to the Torque converter not being locked, you are dealing with the fact that at lower speeds where the aux cooler doesn't have much airflow and you're not running the cooling fan, the trans fluid will get warmed by the coolant in the 'cool' side of the radiator (there's a trans cooler in the rad tank, too).

If thermostat is open (which I'd expect in 90F ambient after a few minutes of operation), the coolant on the 'cool' side of the radiator is probably near 190F, thus your trans temps are near the same value. At higher speeds or with the cooling fan running, the coolant gets cooled more in the radiator and the Aux cooler will take temp out of the trans fluid instead of warming it and the trans will run cooler.

Trans temps below 220F are a 'so what' in my book unless you want your trans fluid to last 200K miles. I've changed mine at 50k and 100k (even though I've only seen near 220F a couple times)

[jmac5058]

When crusing around the countryside like that just pick- up speed (if poss)a little and let the TC lock up at about 46-47 mph and not only will everything run cooler but milage improves also.In that senerio I use manuel mord in 5th