What is the guideline for maximum sustained towing RPM (hills/mountains)?

Truck is a daily driver, but I tow ~6,500lbs several times a year. I ended up trading the 1500 for a 2500 because I... umm.. forgot about 500lbs of payload (topper, dogs, some cargo) and I was at/beyond specs for payload and coming close to max GCWR. Diesel didn't make economic sense for my particular circumstances (not going to start that war ).

There is no redline on the tach, and I'd rather not find out the hard way where the rev limiter is. I have (had; still need to add it to this truck) a tranny temp gauge with the sender in the pan. I plan on driving mostly by tranny temp, but have pulled almost 4,000rpm up a grade in 2nd gear.

4,000 RPM in 2nd gear in a V-8 just "feels" wrong to me. As long as I keep tranny temp under control, where should I start worrying about engine RPM for sustained (say, 15-20 minutes) hill climbing?

I hope this is the right section to post in; I can't find a specific area that looks more appropriate.

Thanks!


2008 Ram 2500 QC 4x4 5.7L Hemi, 3.73 rear
ex 2007 Ram 1500 QC 4x4 5.7L Hemi/MDS, 3.55 rear
ancient beast: '76 Chevy K-20 with SB 400.

 

4k isnt too high for the hemi. its rated at 345 hp @ 5,600 rpm, 375 lb/ft torque at 4,400 rpm so at 4k you havent hit you peak in torque yet. I think redline is 5,800 but cant remember. wouldnt be much higher, so 4k isnt gonna hurt anything m8.

 

I know where the peak torque/hp is at, but are there any problems running there continuously; especially under load?

Thanks!

 

No, that is where the engine is most efficient under a heavy load.