So there's currently nothing wrong with the two speed T170 rear axle which I upgraded from the original oval housing 15,000lb axle that I couldn't get bearings for, back in the '90s. Said axle upgrade came out of a 1967 Chevy C60 and it also got me the wider 15x5" brakes versus the 15x4" that my bus came with. It was also a totally bolt in upgrade, my Dad and me did it in an afternoon. My only issue with this axle is that it's still the slow old 6.4:1 (or thereabouts) high gear ratio and I'm spinning 3650RPM at 65mph, with the 8.25x20" tires at a hair under 37" in height. That's wound up pretty tight for a big 500cid Cadillac V8, and since I do have said burly V8, the 5:81 ratio ring and pinion would get me down around 3380 RPM. That's a pretty notable difference and would make that big V8 which likes to lug, very happy versus the tiny 327 from 1965 that liked to rev.. and spent all its time on hills in low range of third gear. With the big Cadillac V8, it's rare that I actually need to use the low range. The two speed shifts with authority however, and its level of howl in low range is the same as or less than every other one of these rigs I've ever driven or ridden in. Would be inclined to leave-R-be.
One more benefit of the taller gears is that, along with the brand new 22.5" non-widow-maker wheels and radial tires, I could cruise comfortably in the vicinity of 70mph versus 58mph. Additionally, the modern wheels would allow a tire of about 2" greater diameter and the gear ratio calculator says I'd gain a couple hundred RPM lower at 65mph. That's also not nothin,' getting down to a comfortable 3200RPM.
I've Googled my brains out and I can't find a higher ratio ring and pinion. Maybe if I had the part number for said gear set I'd have better luck? I know that they made taller gear ratios, as I've found a used third member out of a '78 C60 that is the 5.8:1, and it's not unreasonable at $1260. However my current setup is really still good, I would be comfortable with putting in the new gears myself, only replacing bearings if they look to need it. But I don't think they're bad, the axle has no clunk when going from drive to float to coast; I've stood over it while friend drove the bus on the highway, and the tires made more noise than the axle, which has just a slight hum, that I don't think is abnormal for a unit this big spinning that fast.
I guess I must just like to make more work for myself on this rig :-D
