6.4L Hemi tow report - weights added

brulaz wrote:

Buck50HD wrote:
Here is summary I put together that might add to this thread.
...

Man, where did you find all the HP/rpm curves?
And the Powerstroke HP goes down in 3rd?
EDIT: the torque curve must really drop off at high rpms
Would love to see the rpm data in all gears.

It's all curves I found in searches or curves I generated from the advertised HP and TQ peaks & RPM. Actually, the 6.4 Hemi is the only one where I had only the HP and TQ peak and had to estimate the curves from the 4 points. The torque curves of the big gas V8's are fairly predictable anyway so it makes it easy. For the diesels, they fall off hard after the power peak so the numbers over 3000RPM are suspect.

I don't work for an auto manufacturer. Just a GM guy that ended up buying a few Ford products recently. I had some interest in comparing capabilities and understanding the strengths and weaknesses of each truck. There are a few (RAM) missing and I'll add if I get time.

One thing I found with my truck is that the 3.73 rear is ideal for holding highway speeds on moderate grades. 2nd gear puts it right at peak power (5200-5500RPM) at 60-65MPH, generating the full 385. A truck with 4.30 rear would be winding away at 6000RPM making less power. Plus, the trans probably wouldn't even allow it to downshift. So, you'd be stuck in 3rd(only 300HP) until you lost enough speed to downshift. In the mountains, it would have an advantage when speeds are power-limited to less than 60MPH. The Ford trans could use less spread between 2nd and 3rd.

The 6.4 Hemi needs a lower 1st and 2nd gear, even with the 4.10 rear. The 3.73 cripples it even more. At highway speeds, it's not possible to get full power. Despite the poor 1st and 2nd, 3-6th are about where you'd want them with 4.10's and have a nice spread.