Transmission not holding gear on decent

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Fort C

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I have a Gen 3 (2015 Limited-6 speed). and came back over Berthoud Pass from Winter Park last Friday night. Roads wer mostly dry. I was in 2W and the transmission seemed to be slipping in 3rd and 4th! The tow haul mode didn’t seem to help. Not sure if I’m starting to have transmission issues??
 

99WhiteC5Coupe

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I have a Gen 3 (2015 Limited-6 speed). and came back over Berthoud Pass from Winter Park last Friday night. Roads wer mostly dry. I was in 2W and the transmission seemed to be slipping in 3rd and 4th! The tow haul mode didn’t seem to help. Not sure if I’m starting to have transmission issues??


Were you towing?

Did you manually up or down shift the transmission, using the manual mode?
 

Timo2824

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In my experience with tow haul you have to depress the brake fairly hard before the transmission will down shift. Once it's started compression breaking it will keep doing it until you hit the gas, then I have to hit the brake fairly hard to get it to downshift again. It defaults to freewheeling, I'm assuming for better milage.
 

rollinstone

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In Tow/Haul the xmsn in my 2014 automatically downshifts without pressing brakes. Sometimes it will downshift to 3500-4000 rpm at which point the engine is screaming so I’ll press brakes steadily and lightly to override it. I learned to never pulse tap the brakes as that interferes with the ABS.
 

Timo2824

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In Tow/Haul the xmsn in my 2014 automatically downshifts without pressing brakes. Sometimes it will downshift to 3500-4000 rpm at which point the engine is screaming so I’ll press brakes steadily and lightly to override it. I learned to never pulse tap the brakes as that interferes with the ABS.
Is this with the cruise on? I usually don't set the cruise coming down big descents, but if the cruise is set and I'm exceeding the setpoint it will automatically downshift. When it's not set is when it seems to default to freewheeling. On my RV with a 6.8L I've seen 4500rpm coming down the mountains. They will usually upshift before hitting redline.
 
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