Eaton 18spd Intermittent Problem

[SquareOne]

My 10 speed Eaton used to do the same thing when I first bought my truck. Had about 360k on it at the time. Mine would occur randomly and only while shifting from High-Low, never Low-High range. It was slowly beginning to get a little more frequent for the first 100k miles I put the truck.

While performing a full PM, I replaced the trans fluid with 75/90 gear oil (from the original 50wt it called for). The grinding began to occur fewer and further between until eventually it VERY rarely happened at all. That trans now has a tick over 800k miles and I couldn't tell you the last time it has ground between ranges.

Seems with the mileage you have, you wouldn't have that issue, but then again, if you have a lighter weight oil in the trans and pulling heavier loads, maybe excessive heat has broken the oil down faster? Just a theory, but maybe try replacing the fluid with a heavier weight gear oil and see if that helps.

Also, just in case you don't already do this, make sure to flip the splitter before making your shift from low-high range or vice-versa.



*** An 09 with 134k? Whats the story there? Could also be contributing to your issue depending on its past use. What kind of hours do you have on your truck?