Towing 4,000 pounds

I towed a sailboat a thousand miles thru hilly country, boat & trailer combined less than 4000 lbs.
My 99 SR5, 4WD, 3400 engine was weak on every hill. Only solution was shift down to second gear, around 4500 rpm to stay at 50 but I thought that high rpm sustained for several minutes at a time was not good for the engine.
It always felt like there ought to be a gear between 2nd and Drive.
Toyota manual says towing capacity 5,000 lbs.
Is that normal for a 99 SR5, 3.4L ?

 

Might be a little rough on the transmission too? I don't know how that tow rating is determined, but I'm not towing anything that heavy out here, ever. I'll probably cap it at 3000 pounds max with the mountain passes here. Welcome!

 

Welcome to the forum.

 

Yes I think its been hard on transmission.
Tranny seems to have 4 gears counting overdrive as a gear, but I faintly feel another gear uphill between Overdrive and Overdrive Off. Not really useful.
There is a very wide gap between 2nd and next gear up, "Drive(OD off)", which requires downshift to 2nd on gradual hills towing 3800 lb., , takes 4500rpm at 50mph.
Does 4th generation have better gearing or more power?

 

The 4th gen V6 had around 270 lb/ft of torque if I'm not mistaken. The 4th gen also offered a V8 with torque up the wazoo. The V8 also came with a 5 speed auto.