The PAC brake isn't nearly as effective with the ECO hubs as it was before. It helps but not nearly as much as the transmission downshifting. The FMTV PAC Brake does have a tendency to seize up - mine did at one point and I had to remove it and "service" it aggressively in my bench vise quite a bit. Hasn't had an issue since but other guys have not had my luck it seems.:
I put about 8,000 miles on my truck before the hubs, and have about 3,000 on it with the hubs and I don't find that the transmission shift behavior needs any adjustment - other than being smoother because it better loads the converter, it's not significantly different other than which gear you are in for a given ground speed. If it shifted sooner it would put you below peak torque in the next gear and that would not be efficient. The transmission doesn't know or care what your ground speed (IE: gearing) is - it's shift behavior is governed by throttle input and input/output speed and it's programming is based on engine specs - peak torque, governed redline, etc. In the Allison software it doesn't even show ground speed that I have found. I have poked around in the software quite a bit and not found anything that I thought would be useful to change....... have contemplated seeing if I could set the PAC brake to stay engaged down into 2nd gear but as I noted the PAC brake is much less effective with the ECO hubs so I haven't bothered. You almost didn't even need the service brakes with the reduction hubs and the exhaust brake but now it just gives you a gentle drag when it engages.
I've done four complete ECO hub installs - two 4x4 and two 6x6 and none of them leak from anywhere using my sealant of choice:
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