Super 10 trans grind downshift from 7/8

Maybe the synchronizer on the tail of the transmission?

 

Usually synchronizers as said.
Sometimes you gotta change the range selector itself on the gear stick too,

 

Is it the shift lever that is grinding when making that shift or does the lever shift fine into 5/6 and its grinding and trying to find a gear after the lever falls into 5/6?

Those transmissions only have the one synchronizer do they not? (Super 10 essentially never existed where I live, nobody has one). If it were the synchro you'd think you'd see it clash on every shift that uses the synchro. Not saying it can't be the synchro, just seems odd it would only show up in one of the five downshifts involving the synchro.

If its the lever that's grinding trying to drop into the 5/6 hole I would probably put my focus on the main box first instead of the aux.

 

That's why they quit the Super 10. They were nothing but trouble. I had one and would always shift to neutral, flip the splitter, and then shift back to into the gear. Super 10's never split as smooth as a 13 speed.

 

I drove trucks with super 10's for 5 or 6 years when I first started trucking and never had any of those problems. I liked them. They quit manufacturing them over 20 years ago probably his is a little worn.

 

That was the only way to make it shift between 9th and 10th. The one I drove had a tendency to shift between 9 and 10 (both ways) at too low RPM.

 

Also a fan. I saw one that went over 3 million miles with just a snychro change when we did the clutch. One owner truck though.

Biggest issue with them, like most, drivers who didn't know how to shift them.

 

Yep that's exactly what I figured... They were actually a fairly common fleet spec transmission back then which is hard to imagine considering today's world.