cruising RPM

[dirtwarrior]

I have a 2011 Chevy Colorado 2.9 4l60 transmission and 3.73 gears
My Mustang is 3.7 6r80 transmission and 3.19 gears
When cruising with my truck at 60 and my Mustang at 60 the RPM is near the same

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[K4fxd]

The truck has taller tires.

 

[dirtwarrior]

With my Mustang what RPM should I see at 60MPH

 

[K4fxd]

Depends on what tires you have. Somewhere between 1600 and 1700 in 6th gear

 

[KeyLime]

With my Mustang what RPM should I see at 60MPH

MPH/(60/gear ratio/final drive ratio x tire circumference in miles)

For my 2021 with a manual (0.622 6th gear), 3.55 final drive and 255/40-19 tires the calculated rpm at 60 mph is 1647.

Having said that there is a bit of slop in tire diameter from brand to brand, pressure, style, etc. So there is a bit of variance in the rpm but not by a lot.

 

[KingKona]

With my Mustang what RPM should I see at 60MPH

What your tach reads????

 

[EFI]

what RPM should I see at 60MPH

Whatever that big gauge on the left reads.

 

[Linkster1666]

I have a 2011 Chevy Colorado 2.9 4l60 transmission and 3.73 gears
My Mustang is 3.7 6r80 transmission and 3.19 gears
When cruising with my truck at 60 and my Mustang at 60 the RPM is near the same

And then....?

 

[dirtwarrior]

What your tach reads????

1750

 

[shogun32]

With my Mustang what RPM should I see at 60MPH

you should have minimum of 2000 RPM on the clock, 2500 is better. downshift till you do.
Unless you're dead or asleep at the wheel. Or mellow as F on grass or something.

I lock out my F150's transmission selectors (so it can't upshift) to maintain at least 2000+RPM at any speed under 75mph on the 3.5TT. I don't even think of using 6th gear (MT82d4, 3.73) till I'm going 80.

SPIN THE DAMN MOTOR. It's designed to do that and more efficient to boot.

 

[KingKona]

you should have minimum of 2000 RPM on the clock, 2500 is better. downshift till you do......I don't even think of using 6th gear (MT82d4, 3.73) till I'm going 80.

SPIN THE DAMN MOTOR. It's designed to do that and more efficient to boot.

Hysterically incorrect.......as long as the engine isn't being lugged, there is no such thing as "minimum RPM".

Tell you what; do 100 freeway miles in 5th gear at 79MPH, and then 100 freeway miles in 6th gear at 79MPH. Check the MPG comparison and get back to me.

We'll see how "more efficient" your theory is. If we're gonna follow that logic, might was well leave in in 3rd at 79MPH.

 

[shogun32]

Tell you what; do 100 freeway miles in 5th gear at 79MPH, and then 100 freeway miles in 6th gear at 79MPH. Check the MPG comparison and get back to me.

already did. on I-66, and granted it was only 25 miles. 5th was more efficient.

 

[KingKona]

already did. on I-66, and granted it was only 25 miles. 5th was more efficient.

I guarantee you it's not. Not even close. 25 miles means nothing, and I-66 is up-hill one way, and down-hill the other.

I'll challenge you to an MPG-off. You use 5th, and I'll use 6th. From Manassas to I-81. 70-80 MPH.

I've got $100 to bet.

 

[Ock]

I guarantee you it's not. Not even close. 25 miles means nothing, and I-66 is up-hill one way, and down-hill the other.

I'll challenge you to an MPG-off. You use 5th, and I'll use 6th. From Manassas to I-81. 70-80 MPH.

I've got $100 to bet.

lol my mpg on that stretch of road was always bad...lol esp once u get closer to 81...

 

[KeyLime]

I guarantee you it's not. Not even close. 25 miles means nothing, and I-66 is up-hill one way, and down-hill the other.

I'll challenge you to an MPG-off. You use 5th, and I'll use 6th. From Manassas to I-81. 70-80 MPH.

I've got $100 to bet.

And the reason that 6th gear is so tall is for meeting fleet fuel mileage goals. If it wasn't more efficient Ford would not have put that in the car. If spinning the engine faster was more fuel efficient Ford would have selected that gearing. Lower rpm's result in a more open throttle plate and reduced part throttle pumping loss as well as lower internal friction losses.

The old Fox Body GT's has some really tall gearing. My '85 was turning 1700 at 70 mph in 5th.

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