Agree on the route to Osoyoos
On the route east on Hwy 3, yes there are a few mountain passes in your way, but people travel over them every day pulling RV's of all shapes and types.
First thing to remember when pulling in the mountains. Only use your breaks to keep your speed in check. Meaning "ALWAYS" use the Transmission of the truck by dropping in in Lower gears when going down long grades in the mountains Use your breaks just every now and then to keep your speed where you are comfortable. When I go down these hills which I do all the time since I live here 70km is my happy spot. I will use the lower gears of the transmission to stay at 70 km/hr and if I start to speed up a bit I will quickly pump the breaks to get below 70km/hr ( say 65km) and then roll on letting the transmission do the work again.
Never ever go down these mountain passes and not use the transmission, you will heat up your breaks they will become mush and then not work when you need them.
Don't be in a hurry and let people behind you push you. Keep to slow speeds take your time and when you get to the bottom and find a wide space beside the Hwy pull over when safe to do so and let others pass.
Always remember in the mountains..... never go down faster than you went up.
You will see Semi Trucks use their 4 way flashes when they are going slow up and down theses mountain passes. That's to show the people coming up from behind that they are moving slow. Don't be afraid to do the same thing if your going slow up and down the hills.
You don't have the age of your truck or model. That makes a big difference when giving advice. If you look at my signature I give the year type and model of truck plus what I am pulling. This will help people give you advice especially like this post when your asking for advice about mountain driving.
My truck ( my new baby ...grin...) has all the bells and whistles for mountain driving like it's a diesel, has a auto / manual transmission which is great for going down hills plus a engeine break.
Now you dont need all this stuff to drive safely in the mountains and I did it for years with an ordinary truck but it sure is nice.
Also when going up these mountain passes drop the transmission into second gear and just plug along in the 70km speed area and relax. As I do t know your truck I am guessing you have a three speed transmission, so take that for what it is worth. You van leave your transmission in "D" (drive) when I g going up these hills but the transmission with be kicking in and out of gears as you go up which will heat up the transmission. By leaving it in one gear and stay at a steady speed, the transmission will stay cooler.
You will notice on BC Hwys there will be signs posted about the % grade of a hill coming up. When you see that sign get ready for a hilll so slow yourself down before you get to the top of the grade.
Then drop the stick for the transmission to a lower gear and let it do the work for you. Again, do t worry about the people behind you just take it easy and drive what you are comfortable with. Like I said I am happy at 70km/hr going down these mountain grades.
The grade out of Osoyoos is a good pull. I did it with my old truck pulling my 33.5 ft 5th Wheel and didn't have any issues. On the east side as you come down the last of the hill you pop into Rock Creek. The speed limit goes from 100, to 70, to 50. Make sure your doing 50, they love catching people coming down off that hill going to fast....
Christina Lake to Castlegar , you will pull a long grade heading out of the lake to the Summit. Put the truck in second gear and just plug along at 70/80 km and don't be in a hurry. The other side coming off the summit is one hill about 1 km long and then a bunch of shorter hills all the way to the Castlegar end. Just before you get here you will come to some "S" curves and then the hill into Castlegar. Again use the Transmission and breaks for check.
If you go around through Nelson and across Kootenay Lake Ferry it willl be a slow windy road, but no hills. From Creston to Alberta it is flat on Hwy 3. There is the Crows Nest Pass but it isn'ts a mountain pass more a cut through the mountains as there are no hills , Crows Nest Pass is windy, not hilly.
Note: all inland ferries in BC like Kootenay Lake Ferry, which is the longest free ferry ride in the world, are free.
If you choose to go over the Bombi Pass between Castlegar and Salmo and over the Salmo /Creston ( Kootenay Pass) it's the same thing you did going over the hill out of Osoyoos and Christina Lake, long and slow.
Soup.