Rpm's @ highway speed

[Graygoose]

99% positives that is incorrect then, a 3.55 rear gear will give you a lower rpm @70mph than a 3.92 and definitely lower than a 4.56 rear gear. Check your math again

sorry, first was not with OD, straight from Randys Ring and Penion site

RPM
--------------------------------------------------------------------------------
Enter Ratio, Tire Height, and Speed (mph) then click Solve to calculate RPM

Ratio Tire Height Speed
3.55 31 70
Auto* AOD Manual 5 Speed
2766 1885 2693 2155
* Auto = D in an AOD
* AOD is calculated at .70 transmission ratio
* manual = 4th in a 5 speed
* 5 speed is calculated at .80 transmission ratio

and true, lower gear will have less highway RPM, but too low will actually decrease gas mileage on some models. A deeper gear ( higher gear ratio) would have a higer RPM range, yet sometimes offer better mileage.

 

[truckin151]

Negative, Ghost Rider.

To me it feels like it is not going into the 2nd OD but I could be wrong. I have been driving an 04 with a 4.7 for the last 6 years.

From whats been said it sounds like a combo of everything,

You probably have 3.92's, add that to the OD gearing and mds kicking on and I think that would be the cause. You shouldn't complain to much though as the hemi's get the best mpg right around the 2200rpm mark anyways, that's like the sweet spot.

 

[bigbadram1500]

Interesting read. I think mine runs around 2k at 70, mds disabled, 3.92's. I'm gonna have to check it out, cuz now I'm curious lol

 

[iSlacker816]

Tho it has nothing to do with a hemi, with my 5.9 and 3.55's I'm right at 2000 at 70mph.

 

[tim johnson]

From whats been said it sounds like a combo of everything,

You probably have 3.92's, add that to the OD gearing and mds kicking on and I think that would be the cause. You shouldn't complain to much though as the hemi's get the best mpg right around the 2200rpm mark anyways, that's like the sweet spot.

Not complaining at all, just trying to determine if it is going into 2nd OD or not. Like I said, I have been driving an 04 with a 4.7 and it just "feels" different.

So far, I am pleased with the 07. Little background info on it:

Bought it in October from my work, the motor was blown. Truck has 199,*** miles on it. Tranmission was repalced with a reman unit 12 months ago. I paid $1200 for the truck as is. Spent $2000 on a salvage yard motor from an 08 with 16k miles on it. One weekend later I have a 4 year old truck with a nearly new drivetrain and it is PAID for!
I am as pleased as can be with it.

 

[tim johnson]

Interesting read. I think mine runs around 2k at 70, mds disabled, 3.92's. I'm gonna have to check it out, cuz now I'm curious lol

How do you disable the mds?

 

[TheSatinPumpkin]

^^ Programmer

 

[rennaissanceman]

Not sure about the gear ratio, and I don't feel like checking, but I'm running just below 2000 at 70 mph