Rpms 2.7 at 70mph

Pm sent

 

Yeah, I thought 65 in 5th gear with no load on mostly flat highway is just right for the for the 2.7 with my stock setup. The road I use daily, has a speed limit of 60.

I got this toy not because its fast, I got it because its unstoppable in the winter.

 

Found a pic of my old setup:

 

I want to ask a related question. 2003 dbl cab, 285s, and a front bumper. 75-80mph pushes 3200rpm sometimes.. should i regear to 4.56?

 

So you want to increase your RPMs by regearing? That is exactly what lowering your ratio to 4.56 will do.

For argument sake lets assume there is a 1:1 engine to rear end turning ratio.
That means with the stock gearing for every turn of your wheel the engine is turning 3.58 times.
Regearing to 4.56 means your engine rpm would increase to that.
That would give you more power but increase fuel consumption

 

@theteleguy are you running the 2.7 or 3.4 with that DC?

 

Correction: More torque, not power.

 

True, the measure of an engine's performance on a dynamometer is given as its torque
Not to be a smart ass but Horsepower is related to Torque and engine RPMs.

Here is the pertinent equation:
Horsepower = (Torque x RPMs) / 5252
or
Torque = (HPx5252)/RPM

A little complicated LOL! (any mechanical engineers willing to chime in?)

Here is a chart comparing the two on the Dodge "Hellcat" V-8



So Torque and Horsepower both increase with RPMs but not proportionately equal.
I see this with my Tacoma.
My ScanGaugeII shows the horsepower increasing as RPMs increase.

 

3.4L, was under the impression that more torque would mean less effort to get higher speed, it appears that was incorrect lol

 

I'm running 32's and at 75 it's around 2300 w/ 4.10s

only reason I ask is 3200 seems a little high unless you're running with the TC unlocked

according to the calculations earlier:

((75 mph x 4.10 gr x 336?) / 33 ) x .71 (final gear in 3.4 auto) = ~2250 rpm

 

Ok so I finallly headded down the road.

Stock 2.7 little elevation change, 31 inch tires, light rain.

5th Gear @ 70MPH is 2760. My GPS speed and Speedo dont exactly match but should be close.

 

All true on a dyno but real life is at given speed the engine power is the same - equal the moving resistance. At 50 mph it doesn't matter if you are on 3rd, 4th or 5th gear the power delivered is exactly the same. However gas mileage will be different as the engine efficiency is different at at different rpm. The swet spot is about 2200 - 2500rpm.

The biggest difference with different differential gear ratio is possible torque applied to the axle. To much and the axle will become the weakest link in powertrain.

 

I got a tach from another board member and got it in today. 265/75/65 Duratracs, 4:56 gears. 70 mph is at 3200 rpms. Not as high as I was expecting.

 

back in the olden days we didn't have overdrives (not commonly anyways) all our cars ran around @ 3 grand.
Now you know why not everyone wanted a firebreathing big block to drive everyday and gears in the 2:78-3:08 range were popular.

 

My truck has 4:56 gears. 70mph is right at 3k rpms. I'm running 265/65/17's.