Hello, I am new to having an Allison 6 speed transmision and am very pleased with the way it works, although I have one concern. My 2008 adventurer gas, workhorse chassi (2400 miles)runs great and smooth except when in 4th gear, at lower RPM I seem to get a vibration up untill around 3400 rpm then it seems to smooth out, I feel it mostly through the accelerator pedal and even thought maybe the engine was running rough? but then again this only acures in 4th gear ... anyone have any ideas? or is this one of those 'have to live with items' (like my Harley dealer continues to tell me)
Thanks in advance Craig

I wouldn't think that was normal and its new so take it to an allison trans. shop and have them check it you have a 100,000 mile waranty.

Thought I would leave an update, turns out when I had the MH dynoed I had two burnt plug wires which I was told was causing the feel of vibrations but was actually loss of power.
Runs better than I ever thought it could now.