F350 SRW Enough Truck

4x4ord wrote:

Cummins12V98 wrote:
" I'm "getting by" with a GM 8.1 pulling a 12,000+ fifth wheel & see no need for anything more. I tow from Calgary to Radium, BC through the Rockies at least twice a year. there are sections with 8% grade & I can maintain the speed limit even on those steep grades."

NOT calling you a liar but over 20,000# up 8% grade at the speed limit I would assume around 60mph is honestly hard to believe.

Maybe 4x4ord can chime in on this.

You’re right Ron, a 20k lbs truck and rv doesn’t go up an 8% slope at 60 mph powered by a 340 hp engine. There is quite a climb coming out of Radium (this is probably the 8% grade being mentioned) but I think the speed limit might only be 90 km/hr. Even so, it takes roughly 100 hp to overcome the drag and rolling resistance of even a small 5ver at 90 km/hr. The rear wheel hp required for an 8k truck to overcome gravity while pulling a 12k trailer up an 8% grade is exactly 234.66 hp. So 335 hp is very close to the required power at the rear wheels. The 8.1 litre GM made as much as 340 peak crankshaft hp at 4200 rpm at sea level. So, maybe 260 hp rear wheel hp at 3000 ft elevation. So if the 8.1 litre had a gear to utilize 100% of hp it could pull that hill at about 42 mph.

Oops, busted! Thanks for the reality check guys. That stretch out of Radium has lots of curves, which are 60 K/hr & the rest is 80 K/hr. Going up that stretch I generally don't have a problem keeping with the speed limit, I just was forgetting the the limit was that low. BTW, the combined weight of truck & fifth wheel is just a bit over 19,000 lbs

My main point was that something like the 7.3 Ford gasser should be quite capable.