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Parker
11-11-2005, 04:59 PM
Have a few questions about my diesel and know many of you have them so hopefully I can get some help.
First, how hard is it on the motor/trans to run it at 80-85 mph? Seems like when the RPM's are over 2500 it makes more noise and seems to be straining.
Second, if I increase the tire size to lower the RPM's at higher speeds, how much towing capacity will I loose? (I have a 9,000lb. trailer.)
Finally, if larger tires are the answer to lower the RPM's at higher speeds, can I offset the tires with a Banks, or other system that will give me back the towing capacity without damaging the engine/trans?
Thanks in advance for your opinions....

PHOTOGLOU
11-11-2005, 05:05 PM
Have a few questions about my diesel and know many of you have them so hopefully I can get some help.
First, how hard is it on the motor/trans to run it at 80-85 mph? Seems like when the RPM's are over 2500 it makes more noise and seems to be straining.
Second, if I increase the tire size to lower the RPM's at higher speeds, how much towing capacity will I loose? (I have a 9,000lb. trailer.)
Finally, if larger tires are the answer to lower the RPM's at higher speeds, can I offset the tires with a Banks, or other system that will give me back the towing capacity without damaging the engine/trans?
Thanks in advance for your opinions....Such a hard question to answer BUT DO YOU HAVE WEIGHT RATED TIRES???? BE CAREFULL... If not and you are towing a load and have an accident and it was because not the right tire rating insurance MAY NOT COVER ANY OF IT..... 80-85 at cruise controll should have minimal turbo boost keeping the eng temp down.. IF FULL THROTTLE temp will go way up and bad for an extended period of time... Weight rating (tow capacity) is based off many aspects BRAKES, TOW HITCH, frame, engine and trans. brakes will be affected the most because there is more rotating mass what is the weight differance???? and so on and so forth.....Did you upgrade to a class 4 or 5 hitch or are you useing a weight distributing trailer hitch setup???

Lightning
11-11-2005, 05:09 PM
What diesel do you have?

Parker
11-11-2005, 05:35 PM
I have the LLY Chevrolet. 2005.
Yes, Jay I have E rated tires. You don't seem concerned about running at those speeds over 2500 RPM's so I will leave it as it is, 85 is the most I need over a long period, with spurts over that. Never any temp issues so far.
Thanks for everything as always,

Parker
11-11-2005, 09:03 PM
I am bumping this in order to get more feedback on the RPM's that everyone here is running, and if you are comfortable running them at higher RPM's.

HighRoller
11-11-2005, 09:55 PM
Are you talking about towing a 9000lb trailer at 85mph? :eek: That's a disaster waiting for a place to happen. Better check the SPEED rating of your trailer tires.

bigq
11-11-2005, 10:27 PM
I think he wants faster speed when not towing,but is worried bigger tires will affect the tow capacity.
Just add the tires and a box. Like has been said a lot of people get the wrong rated tires when they change them and that could be a probel with a heavy load.
If you had a cummins in that thing i would not flench at 2500 all day long, but with the LLy who knows. :D :D

Parker
11-11-2005, 11:06 PM
Not towing at 85mph, regular driving at 85. Do lots of trips to Vegas, and was wondering if the RPM's over 2500 was a problem??

CA Stu
11-12-2005, 12:32 AM
Gear splitter.
Problem solved.
Thanks
CA Stu

mmered8299
11-12-2005, 02:16 AM
You running 3.73 gears? I up my tires to 35" and hated the bottom end power and thats chipped, turbo and exhaust work. Switched to 4.30 gears and have lost of pulling power. But driving at that speed the RPM would be too high. Besides thats too fast in a lifted truck.

scarabrick2
11-12-2005, 07:03 AM
my bros stock 2005 4x4 crew rattles bad over that speed. I think its the fuel rack making a ton of noise over like 2500 rpms. plus, the fuel economy goes way down. we tow@ 70mph a 27 foot hallet. Put NEW radials(trailer load rated) on the trailer and away we go.

STV_Keith
11-14-2005, 08:25 AM
With the modern diesels, you can turn them on the governor indefinitely as far as the motor is concerned. Just watch the water temp. Without towing, it shouldn't be an issue though.

sigepmock
11-14-2005, 09:29 AM
IMO I'd run slightly larger tires say a 265/75 or 285/75, put the Edge or Diablo Sport Predator tuner on it and call it a day. The larger tires will get the RPM's down enough to cruise at higher speeds and the extra Power from the chip will more than make up for the difference.
I run 35's(Load Range E) on a six inch lift and at 75mph I'm right at 2000 rpm. I have done quiet a few mods to the motor/exhaust to get the power up but it tows the 5000lb boat like it's not there.
I think it all depends on how much you're towing. Either way I think your safe with up to 285/75 tires with out seeing a huge power loss and they will definately help with the RPMs.
Just my $.02,
Chris

OLDRAT
11-14-2005, 10:10 AM
The increase in noise above 2500 is the pilot injection shutting off and
normal injection cycle starting. This is normal but kind of annoying.
The pilot injection puts a shot of fuel in the chamber to cut out on the
noise at lower RPMs.
At 75 with stock 245 tires, mine is turning around 2350-2400 depending
on load and wind. Taller tires and a re-cal for the speedo and ABS will
help. Yes, the mileage starts dropping off above 2000. Thats why the
6 speed was introduced this year.
Good luck,
OR

Big Kahunaa
11-14-2005, 10:11 AM
If you are looking to get bigger tires but want to tow look at 19.5 rims or 22.5 big truck tires

hoolign
11-14-2005, 10:22 AM
If you want some great info on diesels , check out dieselplace.com there is a "ask the tech " section which has helped me with some problems very accurately and quickly. There are a ton of guys on there with a great deal of info on everything deisel related...and depending on how deep your pockets are...all the info you'll need to build a 12 second D-max.

onetallhd
11-15-2005, 09:29 PM
I run 37" BFG's with a 8" lift and also have the juice with the attitude monitor. The monitor is great it monitors everything you could want to know. I am looking at re-gearing this next year to 4.11's but that is as low as I will go due to the fact that I do most of my driving unloaded. My truck currently cruises at 70 MPH at 1800 RPM. I usually set the cruise at 2000 RPM which gives me about 83 MPH. Good Luck!!