Mike mjhart853@YAHOO.COM said -

I am planning a round trip loop through the Sierras in California starting next week (starting from the San Francisco Bay Area)
The Sierras have gradual gradients going East, but coming back West is a different story. Last year I took Highway 4 (Ebert's Pass) both ways (most convenient for our planned destination), but the West direction is VERY steep (25% for the last mile close to the summit), so I was down to 1st gear in my fully loaded Westy (temperature gauge running at the high side on a very hot day > 100F and strange sounds coming from the engine/transmission). Also, the approach to Ebert's Pass from Highway 395 over Highway 89 (Monitor Pass) was pretty steep too.

We have an 80 stock Westy and live on Hwy 4 between Murphys and Arnold. We've done Ebbetts Pass/Pacific Summit many times both ways. 108 has some equal, more or less, steep grades westbound. 120 is just a steady, significant grade into Yosemite  where they charge you $20 (unless you have the senior pass) to go through the park but you don't see much. I think 88 is less grade (except Carson Spur) and 50 ( except Meyers to the summit) and 80 are more less freeways. The Sierras are steep - live with it!

I guess bite  the bullet and do 4 or 108 or opt for farther north or south for less grades. Actually the 108/4 short grades are bad but the right angle turns at bottom and top make them worse - or more exciting! They're definitely 1st gear times and pull over to let the big HP iron pass. 

Good Luck and have fun on your trip.

Pete