Eaton 10 speed grinding from hi to lo

Hello all, I have an 04 Freightliner Columbia with an FR-15210B Metric 10 speed direct transmission and a 12.7 liter Detroit engine. The truck has just at 1 million miles. So about a month ago, my driver was in Eloy, AZ and a small shop there called Cornwell/Regan Diesel worked on the transmission because it was stuck in low range. They replaced the synchronizers and bearings in the tailshaft and put it all back together and it was still doing the same thing. They then checked and said there was a snap ring that had popped off so they replaced that and sent my driver on his way (after 5 days). He has driven the truck about 6,000 miles since then and now it is grinding occasionally when it goes from hi to lo. Smooth as silk going from low to hi and also it shifts great sometimes going from hi to lo but about 1/3 of the time it will grind and then clang pretty loud when it goes in. If they really did put in new syncros (which I think they did) are they worn again or could it be something else? Thanks in advance for your input I am new here.

 

That's what I was afraid of. I actually just got some more information today. I talked to my driver and he says it's been doing this the whole time I've had the truck even before they replaced the synchronizers. I have put about 40k miles on the truck since August. Is it possible that it is going in too fast to allow the synchronizers to work? Or is there any other thing that could make it grind? I'm just grasping for straws but I do understand that it seems like it has to be the synchronizers. Thanks for your help!

 

I will talk with him and make sure he is pre selecting. I always was pre selecting when I was testing it and it was still doing it. Next time the truck comes in if it is still doing it I will run some pressure checks and makes sure everything else is good before I tear into it and replace the synchros. Thanks again for all the replies.