06 Volvo VNM Ultrashift II slips out of high gears

Clearly some things my Driver has not told me here, so, there are many answers I cannot provide. However, the problem is, my truck drives through the first five gears just fine, and once it gets to 6th, it "slips" in and out of the higher gears, almost identically to what it would to if the clutch were bad.

Well, the clutch is great. I took it to Volvo and diagnostics show repeated output shaft speed errors, while my output seal was leaking and the sensor was drenched. So, I changed the seal and sensor, and my mechanic sent me a text stating it's having the same problem. WTH? Any ideas what is wrong?

 

Thanks so much. I will look into this!

 

Thanks, man...I appreciate your input as well, and will inform my Mechanic. Also helps me reach the realization I'm gonna have to fire this driver. Her ### has been dramatic since day one, doesn't pre-trip, waits until the truck breaks down to tell me there "was" a problem a month or two ago, etc., and doesn't listen to anything I tell her she's supposed to do until there is a catastrophic problem.

UGH...the truck ran flawlessly, then, suddenly, this and many other unrelated problems. Internal tranny problems don't go unnoticed by the driver without some sign one way or another {or is there something I' missing (?)...I'd love to be corrected}, and a driver who notices and lies/withholds information isn't worthy of trust, IMO.

You guys are the greatest...most folks elsewhere, mechanics included, don't even wanna cough at Ultrashift issues. I'm very appreciative for the feedback and expertise.