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Speedo off at high speeds?

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Old 03-07-2009, 05:51 PM
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Default Speedo off at high speeds?
Opened it up last night while logging and EFI says I was doing 127mph @ 6334 rpm in 3rd gear.
The MPH calculator says 3rd gear on a 4l60e with 4.11's and 275/45/20 tires should be 135mph +-
Which one do you think is right?
Speedo is dead on at 70 and below, i know for sure. I just don't feel comfortable busting out my GPS and looking at it at that kind of speed.

Unless someone wants to go for a ride?
Last edited by viciousknid; 03-07-2009 at 11:06 PM.
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Old 03-07-2009, 05:53 PM
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the calculator assumes a locked torque converter
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Old 03-07-2009, 05:58 PM
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Originally Posted by viciousknid
Opened it up last night while logging and EFI says I was doing 127mph @ 6334 rpm in 3rd gear.
The MPH calculator says 3rd gear on a 4l60e with 4.11's and 275/45/20 tires should be 146mph +-
Which one do you think is right?
Speedo is dead on at 70 and below, i know for sure. I just don't feel comfortable busting out my GPS and looking at it at that kind of speed.

Unless someone wants to go for a ride?
Come on up here to Jersey and I'll take a ride and keep an eye on the GPS...and a hand on the oh **** handle too!
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Old 03-07-2009, 05:59 PM
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Originally Posted by GMCtrk
the calculator assumes a locked torque converter
AHHHH. that makes sense.

Originally Posted by budhayes3
Come on up here to Jersey and I'll take a ride and keep an eye on the GPS...and a hand on the oh **** handle too!
You buy the gas.
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Old 03-07-2009, 06:13 PM
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Originally Posted by viciousknid
Opened it up last night while logging and EFI says I was doing 127mph @ 6334 rpm in 3rd gear.
The MPH calculator says 3rd gear on a 4l60e with 4.11's and 275/45/20 tires should be 146mph +-
Which one do you think is right?
Speedo is dead on at 70 and below, i know for sure. I just don't feel comfortable busting out my GPS and looking at it at that kind of speed.

Unless someone wants to go for a ride?
@146Mph . . .i think you would of heard a loud boooom .. . . and with 4.11 . . .your rpm's would of been alot more higher . .
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Old 03-07-2009, 08:23 PM
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Originally Posted by viciousknid
You buy the gas.
Deal
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Old 03-07-2009, 08:25 PM
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This was done in mexico right?
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Old 03-07-2009, 08:29 PM
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Originally Posted by 00ChevyScott
This was done in mexico right?
just barely
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Old 03-07-2009, 08:30 PM
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Originally Posted by 00ChevyScott
This was done in mexico right?
just barely.
Had to watch for Elk.................


































and mexicans
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Old 03-07-2009, 10:24 PM
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i just looked at a log from the tbss and im at 134mph at 6326rpm and there's only a .25 difference in tire between us.so i think your speedo may be off a hair

at 6800 rpm im at 143 mph
Last edited by andrew383; 03-07-2009 at 10:30 PM.
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