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1987 - 1996 F150 & Larger F-Series Trucks
Tachometer accuracy

1987 - 1996 F150 & Larger F-Series Trucks 1987 - 1996 Ford F-150, F-250, F-350 and larger pickups - including the 1997 heavy-duty F250/F350+ trucks

Tachometer accuracy

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Old

Apr 1, 2017 | 10:19 AM

#1

greenacres36

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Tachometer accuracy

I have a 1988 Ford F super duty and the door indicates that I have a 4.63. Or a code 72 if I am correct on the ratio. My tachometer is reading 2500 rpm's at 55 miles Per hour. The tire size is 235 85 16 dually? It is a five speed with overdrive. According to my calculations it should be running about 2100 RPMs. Which one is correct?

any help would be appreciated.

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Old

Apr 1, 2017 | 10:30 AM

#2

madpogue

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Joined: Oct 2003

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From: Madison, WI

How accurate is the speedometer?

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Old

Apr 1, 2017 | 10:45 AM

#3

greenacres36

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Gps right on money

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Old

Apr 1, 2017 | 11:21 AM

#4

greenacres36

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Actually I just went out and scrape the tag on the axle and it says 5.13. Yikes! No highway driving here.

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Old

Apr 1, 2017 | 11:58 AM

#5

78 PEB

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Joined: Oct 2010

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From: Ideeho

I run my '97 F-Superduty down the highway at 70 MPH with the 5:13's..........she screams at me but the ol' 460 ain't scattered yet!!!!

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