The ’60s brought innovations beyond looks. Most of them came on the 4x2 trucks, such as the industry-first independent front truck suspension. In the 4x4 department, GM opted to use the more modern Dana 44 axle as opposed to the Napco-modified GM H-033. GM retained use of the Timken T-221 divorced transfer case, which NAPCO had also used.
You don’t see this t-case often these days. The Timken T-221 was a three shaft case from the 1950s to 1970 in GMCs. It had a good record for reliability, but because it was not a direct-drive unit, it tended to be noisy and run hot. It was a complicated unit with lots of bearings and was based on a Timken design used in 6x6 trucks. Parts are expensive these days.
found this was interesting says its a Timken t-221 66Gilbert you said something about a Rockwell T221 this article is about Suburban Carryalls 4x4s possibly different?