Transmissions come from the factory with 5 years/750,000 mile warranties if synthetic lube
is installed, and it's changed every 1/4 million miles.
This warranty applies to all HD OTR transmissions. Generally if transmission fliods are
changed as requiired, not run low on fluid, and not badly abused, they last beyond a million miles, sometimes way beyond that.
When considering the purchase of any used class 8, if there is any vibration anywhere, it's
best to continue searching. If there is doubt as to the conditon of engine, transmission or
differentials, the buyer can have the truck dynoed. A dyno generally reveals any engine or
driveline problems. To go a step fruther, one can have oil analysis done on engine, trans
and diff fluids.
The fluids can also be changed in advance of purchase. If any metal particles are in the
bottom of, in this case, the tranny, metal will come out, be visible in the oil watching it
drain with a flashlight shinning on the oil as it's draining. Metal will also be attached to
the magnetic drain plug. Anyway, it's good that you are pleased with the outcome. Sounds
like shes in ship shape now.