Workhorse UFO Vibration in 5th Gear

[NCY-UFO]

Hello to fellow Workhorse UFO owners. I have a 2008 Workhorse UFO chassis. Itasca Latitude 39W. Just turned 70,000 miles. A new engine was installed at 54,000 miles. On my return home from Florida in early March I was getting a vibration throughout the coach when the Alison trans. was in 5th gear. It runs smoothly in all other gears. Pickup, top speed and cruise are all great, except for 5th.
A good friend who has auto. back ground says it maybe the universal joints.
Any thoughts or similar experience with this problem????
Thanks.

[Lash]

Have 82K on our coach and have not experienced any problems like this. Had small head gasket leak at 62K miles and that was repaired but no other major engine work of any kind.

Hope all works out at minimal cost.

Best Regards

[olskool4x4]

I would check the u-joints first, have you greased them? Also check Trans oil level.

[JohnRR]

Since the engine was replaced I’d want to make sure the torque converter bolts are tight as well and while your in the neighbor the bell housing and front motor mount fasteners as well.

[twinboat]

U joint or slip joint wear.

[akpd]

Sounds like torque converter bolts to me as well.