DT12 TRANSMISSION Grinding on downshift

Any update to this?

 

Probably not from OP, his last login was the day after he posted.

I'd assumed he put the truck in the shop and it got fixed, for not much money, otherwise he would've logged back in and #####ed about how much a new DT12 costs.

Feel free to share your issues with the DT12, MrNobody7657, because obviously your resurrecting this thread to gain insight.

 

lol ahh I’m having a similar issue where it has a little mesh on downshifts in odd gears only.. 1,3,5,7,9,11. From what Chat GPT says I’m pretty sure it’s the counter shaft break acting up and not slowing the input shaft down enough to smoothly get in gear even though I just rebuilt it 12 months ago when we did clutch, actuator, split pin, shift controller, fresh trans oil change etc.. Doesn’t happen all the time nor on upshifts. Who knows.. Trans temp doesn’t get over 170 grossed out through hill country and usually stays around 160 or below on normal roads. Worse mistake of my life was going to an automatic.. I seen where Daimler released a field service campaign in 2021 for a software update for DT12 transmissions built between August 2018 and December 2020 and my trucks a 2020. Might need software updated..


https://static.nhtsa.gov/odi/tsbs/2021/MC-10189348-0001.pdf

 

I got a 2020 also, and am noticing some weird hesitation, every now and then 554K miles on mine. Had a PTO installed at 365K miles and I assumed dealer installed new synthetic while it was apart.

I'd do an oil change and filter change to eliminate that wear point. I run 79K gross all the time and usually get up to about 155-160 pulling good hills in the summer.

You actually may have a low voltage or corroded connector on the harness. Unplug the harness and wipe some di-electric on the connections and see if it shifts smoother.

It also could be oil in air tank for the transmission. Check the transmission air tank.