I am posting this for a friend. He has a 96 U295. As soon as it shifts to 5th gear there is a pretty bad vibration. If you are getting on the interstate and you are in the throttle you don't feel the vibration as bad as you go thru 5th to 6th gear. It is more prevalent when driving at a speed where it remains in 5th, but again it seems to start at the point of the shift. You do feel a lesser amount of it in 6th sometimes. Also, it is worse sometimes than others.
I am hoping someone may have had this problem or actually worked on Allison transmissions and seen this before. It may not be the transmission, but with it happening right at the shift point......
Oh, checked the trans for codes, but it showed no codes.
Thanks
Since it's a 96 and a U295, search the forum for P3 carrier bearing as one possibility -
Vibration in rear of coach (http://www.foreforums.com/index.php?topic=2457.msg8364#msg8364)
Transmission Dampener (http://www.foreforums.com/index.php?topic=8387.0)
solved: rear vibration...Now did the outside rear tires get overloaded? (http://www.foreforums.com/index.php?topic=22943.msg176672#msg176672)
I would check he U Joints first, loose or bad wear from lack of lube.
Does it doing coasting down from high speed in neutral?
Krush,
Haven't tried putting it in neutral. I will tell him to try that.