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post #1 of (permalink) Old 06-17-2001, 02:25 PM Thread Starter
 
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Fuel mileage while towing.

Hi guys, this is Nathan from the Toy and dunebuggy boards. I finally got to use my 74 4X this weekend and tow my rail to Sandlakes Or. Its got your typ. SBC with headers, 272* cam, Performer intake, MSD HEI dist, holley 390 CFM 4150, TH350 auto, 3.73 gears and 32/11.50 street mudders. With my rail trailer loaded (1700lbs) and a few things in the truck, I got 6 MPG. This cant be normal.

I have thought about swapping rearend ratios to a 3.23 to give a "30%" overdrive, thus lowering my RPM and increasing fuel mileage. Are these gears availabe factory if I was to search for a new rearend in the wrecking yard (then regear my front later, I dont four by this, plus it has the 203 TC and my front drive line is not in right now anyway).

Just curious. Nathan

http://www.cascadecrawlers.com
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post #2 of (permalink) Old 06-17-2001, 06:56 PM
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Re: Fuel mileage while towing.

that sounds like it could be normal to me. when i tow my 20' boat (granted it weighs a little more than your 1700lb trailer) but i only get 8mpg on my 89 350tbi with 3.73. my buddys dads bronco only gets 5mpg when towing!! anyways - i think that 3.42 is the highest stock gears but im not POSITIVE on that one

Mike ~
* Earnhardt Forever *

89 Chevy K1500 - 350TBI/700R4/NP241 - 3" lift - 33's
post #3 of (permalink) Old 06-17-2001, 09:44 PM
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Re: Fuel mileage while towing.

<font color=blue>If you go to 3.23s you'll loose fuel milage. The motor wont be at a high enough RPM to produce the power to pull your rail. You'll be in the gas pedal more and this will cause you to loose mileage. Throttle input, not RPM dictates how much fuel you use. My truck came with 3.07 gears and I put 33s on it. It absolutly sucked on the highway because the motor wasnt operating in an RPM range where torque is produced. The 3/4 ton axles I put in had 4.10s in them. Even though I went to 36s, the gears allowed the motor to operate closer to its torque peak so I only have to feather the gas to keep moving on the highway. The motor is spinning faster but isnt working as hard so it requires less throttle input, so I get slightly better mileage (mabye into the teens with a tailwind! [img]/wwwthreads_images/icons/laugh.gif[/img])</font color=blue>


<font color=blue>355, SM465/NP205, 14 bolt ff/detroit/TSM disks, Dana 44 HD, 4" lift + trimming, 36" Swamper Radials</font color=blue>
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post #4 of (permalink) Old 06-18-2001, 05:19 PM Thread Starter
 
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Re: Fuel mileage while towing.

Thanks for the info guys, my plugs tell me I am a little rich, so I will lean her out and see what happens.\

Then again, you have to pay to play!!!

Nathan

http://www.cascadecrawlers.com
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