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MSPOIRIER · 05-07-2023, **(Subject: Eaton 18spd Intermittent Problem )**

Good Evening,

I have been working on this one for a couple months now systematically going through checks and repairs but so for no real progress. I have an 09 International 5600 with an Eaton 18spd (RTLO18918B) that has the quick grind coming out of low range to high. Anyone who has been around would say the synchro in the Aux section. My hang up here (and my local Navistar Service advisor Agrees)has been it only happens a couple times a day if that. I have gone through all Eaton Procedures including disconnecting and blowing out lines, replacing filter/regulator, doing system checks with test gauge, checking fluid levels and replacing air dryer filters a couple times. The lube cooler is air to oil so I don't suspect coolant contaminating the friction on the synchro. The thing that has me hesitant to open up the aux section (besides the truck working everyday) is when the truck is in Neutral running or not it does not always shift in. You can hear the normal burst of air but some times it does not "Clunk" in. Sometimes it wont clunk a couple times in a row. When this is happening I am still showing and holding 65psi on the gauge at the range cylinder. I am going to order the cylinder o-ring kit from the dealer tomorrow and try that as my last effort but I am interested to see if there is any new insight from members of the site to see if there is anything I can try that I have not thought of. This problem never occurs going from high to low and the truck only has 134k miles on it. Also if this is relevant being a higher HP truck with very low gears I do tend to shift across the Range without using the splitter. (4H-5H or 4L-5L) I don't see what that would matter but I'm trying to think of everything. Thank you for reading this far!

Sam

SquareOne · 05-07-2023, **(Subject: Eaton 18spd Intermittent Problem )**

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?

MSPOIRIER · 05-08-2023, **(Subject: Eaton 18spd Intermittent Problem )**

Thanks for the quick reply! I am normally hesitant to use oil outside of spec but I do see what your saying. I do believe the current spec from Navistar has 75-90w replacing 50w. When I get my seal kit for the range cylinder I am going to do an oil change as well. Some have mentioned a drop or two of air tool oil at the cylinder to help but that makes me weary because i know oil in the system can cause issues. . Any thoughts?

** Yes its an 09 with 134k but it is a dump truck and does local work, and site work so more hours idling then going down the road. Just over 7k engine hours. I don't remember this issue before the winter so Maybe the truck sitting could contribute to whatever the issue is. There is a chance it is rust or junk in the range cylinder but I don't want to pull the cover to see until I have new gasket.

On a side note the trans is very tight and shifts very well. Even when the quick grind occurs it comes right out of gear and right into the next, no hesitation or trouble. That is what leads me to believe the piston is just not accuating quick enough. Thanks

Aleeex · 05-11-2023, **(Subject: Eaton 18spd Intermittent Problem )**

When my synchro wore out , I replaced it with a new oem unit.

For the first couple months, when the transmission was cold, it would be lazy about going into high range. Eventually it fixed itself

MSPOIRIER · 05-12-2023, **(Subject: Eaton 18spd Intermittent Problem )**

(05-11-2023 )Aleeex Wrote: When my synchro wore out , I replaced it with a new oem unit.

For the first couple months, when the transmission was cold, it would be lazy about going into high range. Eventually it fixed itself

Thanks, I am hoping it doesn't come down to that but I will be re-sealing the range cylinder this weekend. I changed the oil this week to 75w90 and added some air tool oil to the HR air line at the cylinder. Is doing it less but still 1 or 2 times a day. I hope this works because if not AUX has to come out.

Aleeex · 05-12-2023, **(Subject: Eaton 18spd Intermittent Problem )**

Now that I think about it… on top of the transmission.. there’s a breather. Pull it and make sure it’s clean. Mine was clogged

MSPOIRIER · 05-16-2023, **(Subject: Eaton 18spd Intermittent Problem )**

Thanks, I did that a couple weeks ago, breather wasn't bad but I cleaned it anyways. I am going to try the range cylinder Orings today. For 25$ from Eaton it is worth a shot to try one last thing. According to the Eaton manual the "9 Series" which is what I have the range cylinder cannot be removed to change the inner oring seal without removing the AUX. Can anyone confirm or deny this claim? Looks like the fork needs to be removed from the inside. I will remove the cover and have a look to see if I can get the big middle seal anyways..

MSPOIRIER · 05-17-2023, **(Subject: Eaton 18spd Intermittent Problem )**

UPDATE: Removed the rear range cylinder cover and replaced the large outer and small inner Oring on the end of the piston along with a new cover gasket bit could not change the small inner. (Due to the Aux section needing to be removed to pull out the cylinder on "9 series") took for a test drive but I still got a quick range grind on a shift while all the other shifts were fine. I would say no change but I am going to keep running it as long as it does not get worse and try to pull the AUX at the end of the season. I added a couple more pumps of 75w90 and hope for the best. Any other suggestions would be appreciated but we may need to open it up at some point for this one!

MSPOIRIER · 07-07-2023, **(Subject: Eaton 18spd Intermittent Problem )**

I know there has not been a lot of action on this one but I am grateful to the ones who posted help but I will continue with updates in the hope to help someone who is having a similar problem.

UPDATE: the problem is continuing to happen a time or two a day and some days not at all but so I guess the next step is to remove the aux. I do notice I can drive by NOT preselecting the gear and it will never grind If I move to neutral and switch range. Does this help anyone come to a conclusion on the problem? Thank you. I will update as I continue to work through it.