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Cummins 444xt (ish), 0 miles
Eaton Fuller 18 speed RTO, 550K miles (?) unknown history

I got my truck out of the shop on Wednesday. Six months after going in. I'll update my 'moving home' thread when I get a chance...

Driving back to my shop I noticed the trans was noisier than before. More noise when in OD but both that and direct were louder than I remember. Could be that I forgot what it sounded like in six months but I doubt it. The noise wasn't bad at the right RPM, if I let off the pedal or gave it a little too much it got worse

The shop refilled the trans with synthetic. I'm pretty sure it's always had conventional. Should I drain that out and go back to conventional or if it's normal to get more gear noise with synthetic? Possibly there are other issues?

use synthetic if you have temperature extremes, like in cold northern climates. Otherwise, it is not necessary. That choice is dependant upon application.

use 75/90 or 80/90 instead of 50wt too.. 50wt is not nearly as protective for a truck tranny than a decent 75/90 is.