Newly converted 9spd to 13spd issues

Hey folks I’ve got a new to me Peterbilt with a MX13 that was a fleet truck I’m sure that had a 9 speed eaton. They converted the trans to a 13 spd and without splitting gears it works fine. Upshifting from the high split to the next low gear rpm’s drop ridiculously fast and I’m finding I have to feather the throttle a lot more than I remember to keep it from grinding. 5h to 6l- grind and so on. I really don’t think it’s my habits that are doing it but what do you guys think? Is there some sort of programming that needs to be done along with the conversion in the exam or something? A setting that is off that I should look at? Any info would be great, thanks. And fwiw downshifting is no issue. Also no grind from low range to high range. And just a slight “clunk” when splitting to high side in each gear (off throttle and back on again)

 

No programming needed.

Are you making your split and range shifts before moving the shifter?

Any gurgling or weird noises like fluid in the shifter air lines? Range or splitter piston seals can pass oil and cause delayed shifts.

 

Nope. I preselect both the range and all splits. I haven’t noticed any strange noises from the lines but did work through the gears sitting still and it seemed the splitter was inconsistent and weak. Almost like it wasn’t actuating the gear fully. Not sure if that’s an issue. I’ve got a few decades under my belt shifting these and this one something is going on- just trying to save a buck or two here and there. Thanks for replying!

 

I would start with replacing the piston o- rings on the splitter cylinder and inspect the bore.

Figure first half of the life it wasn’t used at all.

 

Agree. Be sure to use the o ring lube that comes in the kit too.

 

Great point guys thanks

 

Try pulling the air line off the splitter cylinder and squirt some WD-40 in there. Reconnect the airline and work your splitter knob back and forth. If it gets better you have at least narrowed it down.

 

I'm going to do try that today. Appreciate everyones replies. Will follow up this evening

 

Maybe the rear gear ratio is to ridiculously high for the extra splits to work correctly in the rpm range of that engine. Instead of it being 300 rpm between splits its only 100 so the splits will actually overlap and become redundant. Was common with many of the twin stick setups so you had to skip shift to compensate. So only a 9 may be needed for that setup.

 

I get what you're saying but then that raises the question why the manufacturer would even install that setup knowing full well the upgrade would be done eventually. Although, there is plenty of other things they do that just don't make sense either!