kdkrause
Redcliff AB Canada
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Joined: 06/06/2006
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I have a question about towing with a 2008 Sierra 2500HD. My truck is the crew cab 4X4 6.0L gasser with 4.10 gears. The trailer is a Trail-Lite TL30BH with a ready to camp weight of 8,000 lbs. I have been using the tow-haul mode and the truck seems to tow mostly in fourth gear turning about 3,200 rpms. I am towing at 60 mph. Is this normal for this truck? The truck has power to spare for going up hills but I thought it might be able to tow in fifth gear on flat land. Am I driving too fast?
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BlackSilver
East of Heaven, North of Hell
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Joined: 12/18/2003
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You may be towing a little too slow! (Is that a 5-speed or 6-speed automatic?)
My transmission in Tow/Haul typically won't grab 6th gear until around 62-64MPH, although it will hold 6th below 60MPH once it grabs it. What I do sometimes if I want to travel at 60 will be to accelerate to speed in T/H, then when I reach 60, momentarily tap myself out of T/H to get the transmission to shift into 6th, then re-engage T/H (which will then hold 6th gear just fine on level ground). Now this is an Allison behind a DuraMax, so the behaviour may be different in your truck.
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reno82
Cardiff by the Sea, CA
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You may not be driving fast enough. If your right at the point of the upshift it may not make that shift while in TH mode. I take it you have the 6 speed. It should pull in 5th no problem, even 6th on the flat. I'm pulling with the same motor except with 3.73 gears. I have no problem pulling in 5th.
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MikeRP
Circleville OH
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Joined: 11/01/2007
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I would like the others said try to coax it into a higher gear. I'd be interested in hearing your experiences once you get used to the tranny and the engine. This is the truck I almost bought and although I love my new Dodge - my wife likes the looks of the GMC better.
I had a similiar experience with my Avalanche even though it was a 5 speed. I could never keep it from towing in 3 rd gear.
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benbovac
KY
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Joined: 03/13/2005
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i agree you may be going too slow. On our 08 Sierra (Duramax) I need to hit around 63 mph for it to ship into OD. It will hold 6th down to around 60 mph. However on the highway, I normally run around 68-70.
BenBovAC
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txdutt
Parker CO
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Joined: 11/13/2005
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with that weight, you can forget about towing in 6th. When I'm towing, I'll lock out 6th gear. If it's flat & there's no wind the truck will stay in 5th if I'm doing about 65 but any hint of a hill or a headwind she'll go down into 4th. My truck has the 3.73 axle, at 60mph in 4th she's running at 3k rpms..
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