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turfin8705
06-20-2009, 12:50
My friend has a 2001 silverado 2500hd ex/lb with a 6in lift 37inch mud grapplers. He also has a stock trans with 180k on it n a efi live tune thats suppose to put 425hp to the rear wheels. Yesterday he was in stop an go traffic for about an hour n realized his trans temp got to 250 degrees. When he went to accelerate and merge onto the highway the tranny slipped really bad. the trans got near 300 degrees http://thedieselgarage.com/forums/images/smilies/gaah.gif. He let it cool for an hour and it drove home. Today he has drove it n its been fine but i know its about to go. Why would the tranny get so hot it even in traffic it just doesn't seem right? :confused:
DmaxMaverick
06-20-2009, 13:35
Welcome aboard!

Sounds like your friend's truck was in "Limp Mode". When this happens, the tranny will be limited to specific gears, usually only 3rd when tranny errors occur. When this happens, most of the power transfer load will be absorbed by the torque converter. This generates heat. Lots of heat, especially with power levels greater than stock. City-type driving will actually make the heat issue worse, as slower driving offers less ability to cool the systems. Maintaining speed generates less heat than acceleration. If the SES lamp isn't on, either the lamp is bad, or the EFI Live program has it disabled.

Your friend's tranny will likely die soon. The lift, oversize tires, and increased power will kill it in stock form.
Mark Rinker
06-20-2009, 17:27
Tell your buddy to try driving the truck in Tow/Haul mode (button on end of gearshift) at all times. This will cause the torque converter to lock up sooner, in all gears except 1st. The overheat was caused by the torque converter shearing fluid at low speeds with no lockup, and is exaggerated by the mudder sized tires.

Your low speed scenario is one I watch for while towing boats. Every once in a blue moon, I'll forget to engage TH mode and do the same thing if stuck in stop and go traffic. Never seen a limp, but have limped other trucks and had them live a long time afterward.

If the trans fluid is burnt and stinky, your clutches are on their way. Change it, but its probably just a matter of time. If the tranny fluid is still bright pink and not stinky, you'll probably get some more miles...i

The oversize tires won't help anything.