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Discussion Starter #1
As I was towing approximately 10,000# trailer down the Cajon Pass this past weekend (approx. 6% grade) in the tow haul mode the transmission downshifted and my RPM went up to over 4,000. I quickly braked and took it out of the tow mode and it shifted and the RPM’s dropped to normal. This was only for about 5 seconds but it really concerned me. :eek:

My question is how do you prevent this from happening when you are towing down a hill like this? I am sure what happened was that as I slowed down with the tow mode on the transmission downshifted and took the RPM’s up. Any recommendations on how to descend a hill like this? Should I take it out of overdrive?
 

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This has happened to me as well, from what I understand is it's ok for it to downshift into the redline area on Tow/Haul mode, redline for downshifting is the solid red/orange. The dashed redline is for acceleration.
 

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This is exactly why they raised the "red line" on the 06s, for people freaking out when in tow/haul mode. I read that the Duramax was balanced up to 5600rpms without fueling.
 

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Yep, the braking redline is the higher one and you're fine. Details in your Duramax manual that came with the truck...at least that's where I read it with my truck.
 

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The Allison TCM and the Dmax ECM will not allow you to do anything that could hurt your engine or tranny. If you are braking and a downshift would cause the engine to spin faster than 4800 RPM, than the TCM and ECM will not allow the downshift.

You're fine, just keep it in tow/haul and cover the tach. :)

Ben
 

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i would like to spin 4800 rpms while fueled :)
 

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Throw a BD exhaust brake on it. No more red line works great. Might be over kill unless you are in the mountains alot.
 

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IIRC you can't do an exhaust brake on the LLY (if that is what he has)
 

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Discussion Starter #20
This brings me to another question. What is the best way tow a heavy load down a hill. I ask because I am planning a trip up 395 to Lake Tahoe this summer and highway 50 (I belive it is Spooner) is about an 8% grade. Do you leave the truck in Drive or do you drop it down to 2nd or 3rd?

Sounds like to me I should leave it in Drive and the transmission will do the work. Is it better to take it out of overdrive and also put the tow haul mode on? I have not towed many long steep grades and just want to be safe.

Has anyone here towed to Tahoe?

Looking for advice from those that tow mountain roads often.
 
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