Hot Tranny, I Think.
05-13-2015, 08:12 PM
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Hot Tranny, I Think.
I've got a 1999 ram 2500 with a 5.9 and automatic. Tranny temp runs about 165 cruising around with no load. Hook up the 27' trailer and the temp climbs up to around 180 at highway speed. In town with trailer 190-210. Is this to high in town? What should it be normally towing a 7000lb load around if this is to high? If to high can I just put a cooling fan on the tranny cooler? Do they make a good aftermarket tranny cooler that will fit in the stock location? Thanks for any help, memorial day is just around corner and want to go camping.
05-13-2015, 08:44 PM
#2
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Sounds perfectly normal to me.
Unloaded temperatures going down the highway in overdrive typically run 60-80° above ambient temperatures. In town temperatures will be higher due to the fluid transferring the energy of the engine to the gears and not the lock up clutch when in O/D. The heavier the load, and the longer out of lockup, the more energy the fluid has to transfer. That means more heat. Anything over 230° and I would start getting concerned.
If you aren't already I would use the O/D lockout button while towing around town. You get two benefits doing that. One is you keep your RPM's up which keeps your EGT's and cylinder pressures low. The other is you get lockup in third gear which keeps your transmission temp lower.
Where is your sensor located? If I am not off my mark based on your temperatures you posted, it sounds like it's mounted in the hot line going to the coolers.
Speaking of coolers, we have two transmission coolers on our trucks. One is up front next to the A/C condenser, in front of the intercooler. The other one is that barrel shaped object mounted beneath the turbo. That is a heat exchanger that circulates engine coolant around a series of transmission fluid tubes inside it.
I also have a camper, and I monitor the temps as well. The only time I got worried was in Vermont when I had to pull a steep grade in second gear. I was able to watch the needle move up as we went up hill, kinda neat to see. Got around 220-225º before we crested the hill and the temps came down.
Unloaded temperatures going down the highway in overdrive typically run 60-80° above ambient temperatures. In town temperatures will be higher due to the fluid transferring the energy of the engine to the gears and not the lock up clutch when in O/D. The heavier the load, and the longer out of lockup, the more energy the fluid has to transfer. That means more heat. Anything over 230° and I would start getting concerned.
If you aren't already I would use the O/D lockout button while towing around town. You get two benefits doing that. One is you keep your RPM's up which keeps your EGT's and cylinder pressures low. The other is you get lockup in third gear which keeps your transmission temp lower.
Where is your sensor located? If I am not off my mark based on your temperatures you posted, it sounds like it's mounted in the hot line going to the coolers.
Speaking of coolers, we have two transmission coolers on our trucks. One is up front next to the A/C condenser, in front of the intercooler. The other one is that barrel shaped object mounted beneath the turbo. That is a heat exchanger that circulates engine coolant around a series of transmission fluid tubes inside it.
I also have a camper, and I monitor the temps as well. The only time I got worried was in Vermont when I had to pull a steep grade in second gear. I was able to watch the needle move up as we went up hill, kinda neat to see. Got around 220-225º before we crested the hill and the temps came down.
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