Sport45 wrote:
wnjj wrote:
You picked one of the speeds where the 4.10 has just changed to next next higher gear. That's where it will have a disadvantage. The problem with your example is there are many more speeds where the 4.10 has the advantage so overall it is more favorable. My chart below will show those areas where the 3.73 is still pulling after the 4.10 shifts.
Will the 4.10 still have certain hill/weight combos where it performs more poorly than the 3.73? Yes, when you are between gears (as in just shifting up) you aren't able to get the engine up to its higher RPM HP.
The difference between available HP and HP demand is what provides acceleration. When you look at the chart from an RPM in each gear point of view, notice how for every point on the RPM range (the slopes are each gear), the 4.10 geared truck has a greater HP advantage because it's there when the HP demand is lower.
The peak of each RPM is 5000 (my choice) and the valleys are ~3000 for the 1-2 shift and ~3350 for the 2-3 shift based upon the 6-speed ratios I used.
Note: I don't expect these actual speeds to match any particular real truck but to simply illustrate the difference. I just used ~35mph for 5k rpm in 1st for the 3.73 truck and 300 ft-lbs flat across 3-5k rpm.
Interesting. So if you're on a hill that requires 250hp to maintain 55mph the 3.73 will let you drop a gear and do it, but the 4.10 gears rev out and limit you to 50mph.
I have 3.73 gears in my F-250 and would have preferred 4.10's. But Ford only allowed 3.73 and 4.30 at the time and I didn't want to go that low.
From the graph, I see the 4.30 axle doing better than the demand through out the graph. The 3.73 falls short of demand around 58 mph. However it does have ranges of 5 mph, here and there, that it does better than the 4.30. BUT the 4.30 does much better the majority of the time and always stays above the hp demand for the speed, that the 3.73 can't.
