We hope to camp in the valley so would have to cross what looks like some mountainous terrain to get there. Wondering if there are steep grades to navigate. We're experienced in driving mountain highways, but do want to be prepared for the extra load going up steep inclines and the wear on brakes going down. We once had a case of serious smoking brakes going down a long steep grade and don't want a repeat!
And if you have any other tips about Yosemite, feel free to toss those in too!
MountainTop: our very first RV trip was in a rented 31' Class C motorhome to Yosemite, and we had a blast. As others have noted, check on length restrictions for the RV sites in the park. I think Upper Pines Campground was the only one open in the winter (we were there in December) that could accommodate that rig, and it was a tight fit.
If you are in fact coming in from the west, I'd suggest Hwy 140 through Mariposa and El Portal, rather than Hwy 120 through Buck Meadows. We came in on Hwy 120, not knowing any better--it's a steep climb with many hairpin turns. Hwy 140 is newer and a bit gentler.
We've been in the mountains of Colorado for almost two months now with our current (and much larger) rig. Like you, I was worried about mountain driving, but as long as you have a capable tow vehicle, it's not a big deal. If your truck has a Tow/Haul mode, be sure to engage it. Going uphill, take your time and downshift if necessary to keep the engine from straining, even if that means you get a lower speed. For downhill grades, be sure you're at or below your target speed
before you start downhill. Read your owner's manual and be sure you know how to use your transmission to have the engine do most of the braking. We've driven miles of 6-8% grades, and if you do it right, you barely have to use the brakes at all. We took lessons from RV Driving School, and our instructor taught us that on our F-450, if we engage Tow/Haul mode and set the cruise control at about 5 mph below our desired speed, the truck will manage the speed downhill almost on its own just with the transmission. I was skeptical about this, but I tried it and it works like a charm. If you do have to use the brakes, use brief but very firm pressure on the pedal to slow down quickly, then release the pressure--don't ride with your foot on the brake pedal, or the brakes will get too hot. If you're having to brake a lot, downshift to a lower gear.
Have fun! Yosemite is one of the most beautiful places on this earth!