Carl_722
Warminster, PA
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I know I have mentioned gear ratios before but I am getting closer to making a decision.
I am thinking about 4.56 or possibly 4.88 gears in my truck. It is not 4x4. I also am considering going up one size tire to a 265/75/16 if I make the gear change. I found a load range E in that size that I like. Now my truck I use in town when weather is not good for the motorcycle and every time it hits the interstate it is towing the camper so hwy mileage is not a concern. The in town mileage I don't think will suffer but towing mileage I think would improve. I want to bring my peak torque (4,000 RPMS) to 65 mph in 3rd gear. I pull through the Appalachians every time I leave PA and want better power and mileage in the mountains towing.
Anyhow has anyone else done the 4.56 or 4.88 swap to improve towing performance and not had to do it for huge tires? I am interested in knowing how much difference power wise it will make and any change in mileage.
2004 Chevy 2500 LT Crew Cab 6.0L, 4.10 gears 8600 GVWR 16000 lbs GCWR 10300 lbs tow rating.
2006 Crossroads Cruiser CF32BL 34'11" 3 slides.
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terrybk
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I have a 2000 2500HD and have considered swapping my 4.10's for 4.56 or 4.88 (if they will fit). The 4.56 would be a 11% RPM and torque increase and the 4.88 would be a whopping 19%. I am just afraid it will be screaming going down the freeway on non-towing cruises.
That and I have a 4x4!
I would be curious too what others have experienced. I want more torque at lower speeds. As it is the 4000 RPM peak is at about 35 in first and 55 in second. I'd like to drop that down to 25 and 45-ish.
2000 Chevrolet 2500HD Ext LB 6.0L 4:10
2002 Arctic Fox 24-5N
CEK0515 and two dogs
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Carl_722
Warminster, PA
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It looks like the 4.88 gear would bring an increase of 500 rpms over 4.10's in 3rd gear.
http://4lo.com/calc/geartable.htm
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Sundowner1
Chesapeake, VA
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Carry a box full of money for fuel. 4.11 gears are all you want with the 6.0. It really likes fuel.
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04 Chevy2500HD, Duramax, ext cab, short bed, 4x4
08 Fleetwood Quantum 325rkts
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Carl_722
Warminster, PA
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I have the 4.10 gears with my 6.0 and I want more. I am sure the 4.56 will not use more fuel towing. The 6.0L uses less fuel than the 5.7L did that I used to tow with. It does use more than a D'max but my fuel is cheaper. I get 7.5 mpg in the mountains and 10 mpg in the flat lands towing my 5er. I want more power from the truck and the gears are the first on my list of things to do. I don't pull a camper concerned about my mileage. It has got 19 mpg at 55 mph on the highway and 16 mpg at 75 mph. I get 12 mpg around the city. Anyhow I am not willing to trade trucks to get a d'max so I am just going to spend the money on my truck. I like my truck. I do all of my mechanic work except for gears I will have those done. After the gears I am going to do the exhaust and then a cam change after that along with a custom tune for my work.
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Thud
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Carl_722 wrote:I want to bring my peak torque (4,000 RPMS) to 65 mph in 3rd gear.
No way to get to 4000 rpm in 3rd gear at 65 mph as this would require a 5.79 gear with the 265 tires.
At 65 in 3rd, the 4.56 will give you 3152 rpm and the 4.88 would have you turning 3373 rpm.
If you stay with the stock 245's, the 4.56 rpm would increase to 3265 rpm and the 4.88 to 3494 rpm.
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Carl_722
Warminster, PA
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I started looking a little harder at that chart that one in misprinted that showed 3838 with the 31" tires. They got their 3 and 8 mixed up. I don't think I can handle a 5.79 I think I would settle for 3,500 in 3rd gear at 65 mph. That chart isn't completely accurate for an automatic though. The auto in 3rd will turn a little more than a stick in its 1:1 gear.
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Thud
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245's....30.5 in
265's....31.6 in
Carl_722 wrote:The auto in 3rd will turn a little more than a stick in its 1:1 gear.
Nope, converter locks in 3rd so rpm will be the same.
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Carl_722
Warminster, PA
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Anyone with experience pulling with these gears and normal tires?
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terrybk
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Carl_722 wrote:
...
After the gears I am going to do the exhaust and then a cam change after that along with a custom tune for my work.
I've been looking for a 6.0L cam that will push the peak torque down to a lower level but none of them really do that by any significant amount.
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