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It will go just as fast up hill in 3rd gear now as it did in 4th gear before the drive axle change. Running the engine at a lower rpm is a good thing. Makes it last longer and it is quieter.
If you have one of these engines-8.2DD-put a turbo boost gauge on it. This will you an idea of how much power you are generating at any given speed and load. With the 6.14 ratio we pulled 3 to 4 pounds of boost on level ground at 2900 rpm. Now it is the same, if not lower, so I don't think the engine is working any harder.
The thing we have to pay attention to now is the transmission temperature. Since the engine is running slower, the transmission is circulating fluid slower also. This means that it runs a little warmer. On level roads it actually works better. Evidently the extra heat brings it closer to it's designed operating temperature. But on hills it wants to overheat....cook.....roast...broil......smoke.......you get the idea.
We can go up a 5% grade at 55 in third. It is a little quiter at 50 though. Before it didn't matter. It went 55 all the time. It didn't know what a hill was.
I was running 2900 rpm at 55. Now we are pulling 2200 rpm at 60. We replaced the drive axle.
According to the book the torque peak is at 1700 rpm. This should be the ideal speed to run the engine. Don't know if I have the guts to gear the engine for that speed.
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