Quote:
Originally Posted by kerry edwards
Total weight of everything (including the trailer) was somewhere between 1800-2100lbs with about 1100-1200 lbs in or on the car and the rest in the trailer. Went from Denver to Bluff, UT and back. Despite the fact that this load seems to be within the limits of the TD, it seemed to me that it was overloaded. Coming home over Vail Pass and the Eisenhower Tunnel on I-70, it was laboring. Climbing those passes it was 30mph or so, in second gear around 3k rpm's.
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There is this deal that is necessary when you have hills and heavier loads.
It's called horsepower.
If you want to climb a specific grade at 30 mph, you need a certain horsepower. Let's say it's 15 hp. If you want to climb that same grade at 60 mph, you need close to 90 hp.
Since we are severely limited in horsepower, an unloaded vehicle with a 617 might climb a 6% grade at 63 mph. Load the vehicle up with 1200 lb. and it has no chance to hold 63 mph on the same grade. With only 85 hp at the rear wheels, the vehicle simply doesn't have the horsepower to lift that load at highway speeds.
Naturally, you get maximum horsepower at 4500 rpm, so, you might have been able to push it a bit faster in second gear, if you so chose............unless the load was so great that 30 mph climbing speed was the absolute limit. If so, then you'd need a gear between 1st and 2nd to get the revs up to 4400 for the best climb speed. I realize that you would prefer not to run the engine that fast.
For reference, I've had the SDL on a long 6% upgrade with minimal load. It's got 150 hp and it can barely hold 70 mph on such a climb.