So my 05 T1N 158 with 120k miles and is doing weird things. Here's the history.
I started with the classic RSN vibration
New driveshaft that didn't help.
It was finally fixed by the darf repair (thank you Dr. A.)
Then I still had a drive shaft speed vibration starting at about 50 mph.
It does it in neutral with the engine off rolling downhill as well.
I had my new driveshaft turned at a driveline shop and they did some minor tweaking but said it was okay.
Then I took the old driveshaft and put it back in to see if that changed anything and it made the vibration much worse. Vibration started at about 35 mph
Put the "new" driveshaft back in- back to 50
After doing some reading I change the tranny fluid with the high-end Dodge – Mercedes product. I noticed a slight improvement but nothing remarkable.
My thought now is to remove the driveshaft from the transmission and run it at about 55 mph and see if the vibration is still there to try to isolate the problem.
Any input would be appreciated! Thank you very much in advance.