89 from 395 has a very sharp elevation change to the summit then a steep decline. Hwy 4 has some narrow, steep spots. If I was doing that trip with your rig, I might go the extra distance to the Hwy 88 junction near Minden. 88 will take you all the way to Jackson. This is a beautiful highway. There are some steep spots but not too bad.
Yes, I agree that 88 is the better option. The highway was widened and straightened a few years back and is a much better drive than previously.