My truck had the shutter at 1500rpm and was more noticeable at uphill grades. But in addition to this shutter was a vibration that started around 60mph and increased with the speed.
I went under and started inspecting the drive-line/u-joints. I found the u-joint on the front shaft by the transfer case was shot. It had lateral movement of almost a 1/4".
To be sure I removed the propeller shaft from the truck and took it for a test ride. Shutter and vibration are gone. I will be replacing both since I have it out the other one looks like it doesn't have much life left. The seal is starting to leak.
So in my case it looks like the shaft being out of balance was causing the tranny to shutter.
webmastir wrote:how do i differentiate the shudder/vibration at 45mph between a failed tranny versus a failed u-joint?
if i accelerate or decelerate the shudder/vibration goes away.