Gear Ratios

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Dec 17, 2003 | 12:34 PM

Rotorman

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Gear Ratios

Hello there,
Went to the dealer to order my new F-150 4x2 Lariat. I wanted to spec the 3.55 limited slip rear end, but the dealer only had 3.73 limited slip on the lot. Went to another dealer, they had the 3.55 limited slip. I drove both trucks and with the cruise control set at 70, the trip meter was reading 14.9mpg on both trucks. (5.4 V8 in both) I am confused, how can the milage be the same on both trucks at the same speed, when there are two different gear ratios. I called FoMoCo's customer service dept. and they did not have a clue...keep talking about the EPA milage ratings..So I decided to post here, and get an answer from the real experts!! Thank you in advance for your help. Rotorman

= reaction to Ford Customer Care

= reaction to dealers...

Dec 17, 2003 | 01:00 PM

JMorri

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Joined: Jul 2003

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It's only the computer reading you were looking at which is basically a guesstimate.

Did you get a chance to see what rpm's both engines were turning, that's the real guage.

Dec 17, 2003 | 01:32 PM

Rotorman

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Yes I note the RPM on the 3.55 was right at 1975 RPM at 70MPH..but I did not, or can't remember the RPM on the 3.73. I agree that the RPM is the real number, however the fuel flow is quite acurate, at least from prior experiance. Thanks for your input. Rotorman