I spent 25 years developing HD automatics at Allison.
Fresh fluid is always your friend.
I will agree it’s important that it be done correctly.
We referred to the typical dealer transmission flush as “wallet flush”
18 months of quiet... but here goes...
I just bot a Mercedes E320 Wagon in Sacramento California, drove it to a bunch of junkyards on Rt 99, filled it with old dusty Cheby Teeruk parts and Corvair parts.
I decided before I left for home to change the very dark tranny oil. I know all the arguments, but my belief is that folks change the oil when a problem creeps up, so they surmise the fresh oil led to a failure. I never believed there were scrubbing bubbles breaking loose sludge.
So I dumped the mud, and drained the TC as well, got 7 qts out in total. I used FEBI made in Germany oil from NAPA, $9 a qt + tx. I was advised to use Valvoline Max Life at $7 a qt, but I splurged on the FEBI.
I had a 3,000 mile drive home... So what do you guys think happened?