I was driving up a 8000ft mountain with no load @ 2000 RPM @ 60 MPH and the trans temp hit 250F before the engine defueled and finally came down to about 180F, and the weather outside was 40F. Any thoughts?

 

WOW my built trans never sees 180 and thats if im sitting in a drive thru or towing. driving empty i see around 160. 250* i would definately change fluid after that im sure that it is breaking down from the heat.

 

My temp prob is also before the cooler.

 

Could you tell if your TC was locked or not???

Sounds like it was unlocked and depending upon how long the grade was and how much your converter slips when unlocked will determine how hot and how fast it will heat up.

If it was locked and still overheated it, then you have a serious problem internally, maybe the check ball got clogged or something else.

 

I can't tell if it is locked or not, can anyone exlain how to tell. I also see about 190 everyday in town driving.

 

Were you in tow/haul mode???

At 60mph and @2Krpms, I suspect you weren't locked, and sustained driving uphill while unlocked with your tires can do work to some trans parts.

One way to tell, is go up a hill in normal mode and be around 60mph, then hit the T/H button and you will notice what feels like a shift, and thats the converter locking up. Also is on flat ground and cruising around 55-60mph, and you try to accelerate your rpms will rise faster than your speed, then hit the T/H button and wait for it to lock then try it accelerate again. You will notice that rpms go up as speed does.

Third way, is if you have a trans temp gauge, when you are unlocked, your trans temps will begin to rise, if you are locked they will actually begin to level out or drop. When I am driving around normally I see temps around 100* above ambient when the converter is unlocked. When the converter is locked my temps are anywhere between 40-60* above ambient.

So while driving around on a 50* day I see trans temps in the 130-150* area when the converter is locked. and when it is 80* outside I see 170-190* regularly.

Watch your temps while you drive, when they begin to fall, most of the time the converter has just locked, pay attention to when that happens and the feel of it, and after a while you will know when its locked without even looking at your gauge.

Sorry so long...took me a while to figure it all out myself!!!

 

Thanks, I see the same on my gauge as you do with the ambient outside temp in normal driving conditions. But there's two times (one last night) where the ambient temp was 40* and I was climbing a hill and the temp hit 250*. I'll have to try the tow/haul mode to see when my TC locks.

 

Check out posts 4 and 5, from TexasCTD...

https://www.dieseltruckresource.com/...t=tranny+fluid

 

You have a trans problem somewhere. No way should you have hit those temps empty. The TC is either not locking or another problem is surfacing and causng it. Anything over 50 mph you shoul have the TC locked, TH or not.

 

Those charts are grossly misleading and out of date. The info does NOT apply to our transmissions or fluid.

 

My tranny rarely gets hotter than 190 when towing 20k, normal driving and it stays around 160

 

It happened again last night. Climing a hill and the temp went to 250*, I then put the tranny in tow/haul and the temp droped down to 180*. It was also 9* ambient outside and snowing, my 4X4 was engaged.

 

it sounds like your TC isnt locking. There was a recent TSB about these tranny's not locking and the shiftpoint was changed. My 04.5 is like that. my TC will not lock unless i hit 57MPH or if i have my tow/haul engaged it wont lock until 53MPH. a lock-up switch fixed that problem, but i dont suggest that on your new truck.

Like what was said earlier, seeing 2k RPM at 60MPH isnt right.

 

Sevir,

Are you a Coastie?

 

SCCSURF...
Your temps are way to high. I have a probe in the hot line (before trans cooler) and have never seen 200 deg. Often on a warm day I will see 180 but never over 200. There is something wrong. I have driven all over the area you live through Auburn up to Donners pass through Hwy 49 ect. never those temps.