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Old 07-16-2013, 10:38 AM   #1
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Gear Ratios

Does anyone change out rear end gears to get better gas mileage? Posably go from 4:10 to 3:90s

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Old 07-16-2013, 01:41 PM   #2
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Changing out a gear set could , marginally improve fuel economy , but the increase could be so slight that verses the cost of the gears it might never be repaid in fuel savings .
The drop in acceleration rate, downshifting to climb hills instead of holding a higher gear.
The 2 major factors in diesel MH fuel economy are driver habits and route selection. A light foot and staying on major highways to maintain a reasonable cruising speed will get the best mileage.
Any savings from the slight ratio change your suggesting could be accomplished by slowing cruising speed by 3>5 mph , achieving the same cruise RPM drop.

99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
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Old 07-16-2013, 05:38 PM   #3
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Thank You
Good advise.
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Old 07-17-2013, 07:50 AM   #4
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Just my 2 cents... I had a 1994 Chevy 2500 Z-71 with a 3:73 rear and 350. It pulled my 18' enclosed trailer great. In 1997, I ordered a 1998 2500 Z-71 350 but had ordered the rear gear, (I think it was) 3:42 rear, thinking of a more fuel efficient vehicle. Without the trailer, the truck was fine but fuel milage didn't improve very much if any. The sad part, I had to pull my trailer in D instead of OD. In OD, it would shift down on interstate overpasses. After 22,000 miles, I traded it off.
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Old 07-17-2013, 05:28 PM   #5
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Here is another solution:

Gear Vendors under/overdrive transmissions the most awarded auxiliary transmissions.
2001 34' Alpine Coach
2008 Jeep Rubicon or 2012 Ford F150 4x4 Lariat towds
or a couple of different trailers
Retired in Apple Valley, California
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Old 07-18-2013, 10:42 AM   #6
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I believe the most common gear ratio on the F53 chassis is 5.38. A few years ago Ford started making different gear ratios depening on the weight the rear axle was rated to carry. The ratios for the 2013 and 2014 models are:

The 11,000 and 12,000 lb rear axles have a 4.30 gear ratio

The 13,000 and 15,000 lb rear axles have a 5.38 gear ratio

The 17,500 lb rear axle has a 6.17 gear ratio

2013 Adventurer 32H
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