Hmmmmm. We've been through the Eisenhower tunnel with our rig (east to west) and toad, but didn't get slowed down to 15 mph. The V10 wouldn't handle 2nd gear, but once in first it would run up to 30 mph if you wanted to wind the engine. We settled in at 25 mph. Our toad weighs 5000 lbs too.
Coming west up to Wolf's pass, was about the same----although there were stretches where it would pull 2nd gear for a while.
We drove part of the "Million Dollar Highway" in our toad. While possible, I wouldn't want to do it in my MH pulling a toad. However, I would suggest spending a day or two in Durango and drive the highway in your toad on one day and taking a ride on the steam locomotive powered train on another day.
Wolf Creek Pass on US 160 isn't hard. It's mostly wide with a climbing lane and very good shoulders. The climb is about 8 miles in either direction and so it's actually easier on your rig than I-70, even from I-25 in Walsenburg, where you pick up 160. There are ways around US 550 (The Million Dollar Hwy.) that are not very daunting, namely CO 145 via 160 in Mancos to Dolores, Rico and Telluride to Ridgeway (or the reverse). It's a pretty drive and not scary. We've done 550 from Durango to Ouray a lot with a fiver and in the MH. It's a matter of concentration and the truly hairy sections are not that long, but I will say, they are VERY impressive! 550 between Durango and Silverton has been widened and some guardrails added in the last few years. There's really only one spot on that section that gets your attention. Speed limit signs are very accurate for big rigs, so as long as you observe them, you will be fine.
Used to drive underpowered trucks (heavily loaded Paystars w/DT 466) in that region. With those rigs, I would go to Walsenburg then take Hwy 160 west. Fairly tame to South Fork, (La Veta pass will be 9000+ ft) then you'll have Wolf Creek Pass. Definitely not as scenic as coming in from the north. Just about every pass into Durango will be 10,500 ft plus elevation unless you come in from NM.
Definitely the way to go. My first post and this one wiped out my comment. HOpe it sticks this time.
Get a copy of Mountain Directory Guides . Check out their website 1st then order a copy if you think it will be helpful. Also, lots of mountain driving tips on their site.
Tom & Jan
Full timers since April '06 - 2 fur kids (George - mini Aussie, Archie - mini Poodle.)
2006 Beaver Patriot Thunder towing 2012 Subaru (4 down)
Started workamping Sept '07 - "This isn't too bad. Think we'll do it some more."