07.5 LMM towing issues - Chevy and GMC Duramax Diesel Forum
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Old 05-31-2010, 09:03 PM   eBay Motors  #1 (permalink)
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07.5 LMM towing issues

I just returned from a camping trip with my family. We were towing a 26ft toy hauler with 3 quads and the related gear, no water. I'm towing with an 07.5 2500 Duramax LMM 4 dr swb 4x4 with 305 55 20 Coopers zeon xts. I kept the speed around 60-65 mph indicated and calculated the fuel mileage at approx. 7-8 mpgs. Does that sound right to anyone? I expected better out of the truck since I sold my 05 GMC Yukon XL 4x4 with 8.1 liter and 4.10 gears and that was getting 6-8 while towing.
I also noticed the temp gauge would rise to about 220 or so before the fan would kick on and then it would drop back down to 210. Is this normal? I was towing through some mountainous terrain in central to southern Nevada, outside air temp was approx. 80 degrees and was I was not running the truck hard. Trans temp was right around 190-195 the whole time. The trans tunnel in the cab did get relatively hot to the touch also, is that normal?

The truck has 44K miles; a Banks cat back exhaust, cold air intake, deep sump trans pan, Cognito arms and accessories, Bilstein 5100 shocks, airbags, tonneau cover. Should I look into a tuner and a DPF delete pipe? I've also read that I maybe should have put on a larger pipe from the turbo out?
thanks for any help.

rusw1
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Old 05-31-2010, 09:09 PM   eBay Motors  #2 (permalink)
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i would go with a dpf delete if your looking to gain mileage
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Old 06-01-2010, 12:05 AM   eBay Motors  #3 (permalink)
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rusw1, take it to dealer and check for updates for your truck. How much lift do you have? The higher, the less fuel mileage. Your tire size will affect mileage if you can't get moter to 'sweet spot' while towing. About 1600 rpm's. While towing, you should be in the 12-14 range unless your trailer is VERY tall.
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Old 06-01-2010, 05:05 AM   eBay Motors  #4 (permalink)
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Did you have it locked out of 6th gear?

I get the best towing MPG's between 1800-2000rpm's
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Old 06-01-2010, 05:12 AM   eBay Motors  #5 (permalink)
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the overheating is from the DPF...at least mine was. took it off and have never heard that fan kick on again.
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Old 06-01-2010, 06:04 AM   eBay Motors  #6 (permalink)
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Sounds like you're a great candidate for a DPF delete. Shouldn't see any issues with getting hot once you get rid of the DPF. The taller tires will hurt your mileage a little bit, but you shouldn't be seeing that bad of mileage

What brand of intake do you have? Some of them are actually worse than the stock intake and will pull in hot air from the engine compartment rather than cool outside air, like they're supposed to. This can increase engine temps and fan activity.

Let me know if I can help you out with the DPF delete. I run a DPF free LMM personally every day, so I can answer any questions you might have.

-Jesse
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Old 06-01-2010, 04:39 PM   eBay Motors  #7 (permalink)
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i pull a 35 foot 5th whhel that is 12-4 tall --- keeping @ 55 i get 12 and that running under 1500 rpm with the tow/haul set--- as soon as i go fast - the fule gauge runs down as fast as the truck --- pulling 70 or i get 8 mpg


I run 280/17 tire and have the full Banks set up!
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Old 06-02-2010, 08:46 PM   eBay Motors  #8 (permalink)
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hey dirty jeep, what do you mean "locked out of 6th gear"? Tow haul mode on?
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Old 06-02-2010, 08:53 PM   eBay Motors  #9 (permalink)
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gr8shot,
I am interested in a DPF delete pipe. I'm already running the Banks CAI and Banks Monster exhaust. What type of tuner do I need? Should I replace my downpipe from my turbo? Will I still be able to pass annual emissions check or will I have to come up with a work around?

thanks for your help
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Old 06-02-2010, 08:56 PM   eBay Motors  #10 (permalink)
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Quote:
Originally Posted by rusw1 View Post
I just returned from a camping trip with my family. We were towing a 26ft toy hauler with 3 quads and the related gear, no water. I'm towing with an 07.5 2500 Duramax LMM 4 dr swb 4x4 with 305 55 20 Coopers zeon xts. I kept the speed around 60-65 mph indicated and calculated the fuel mileage at approx. 7-8 mpgs. Does that sound right to anyone? I expected better out of the truck since I sold my 05 GMC Yukon XL 4x4 with 8.1 liter and 4.10 gears and that was getting 6-8 while towing.
I also noticed the temp gauge would rise to about 220 or so before the fan would kick on and then it would drop back down to 210. Is this normal? I was towing through some mountainous terrain in central to southern Nevada, outside air temp was approx. 80 degrees and was I was not running the truck hard. Trans temp was right around 190-195 the whole time. The trans tunnel in the cab did get relatively hot to the touch also, is that normal?

The truck has 44K miles; a Banks cat back exhaust, cold air intake, deep sump trans pan, Cognito arms and accessories, Bilstein 5100 shocks, airbags, tonneau cover. Should I look into a tuner and a DPF delete pipe? I've also read that I maybe should have put on a larger pipe from the turbo out?
thanks for any help.

rusw1
Is your speedo reflashed for the taller tires? if not that why your milage is so bad....I was shock two tanks ago I eeecked out a 15mpg tank.....:rockin
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