Hi everyone
I have my 2001 cummins giving me a problem. I bought the truck with a slipping automatic transmission and trouble getting out of first gear. I dropped the pan and found no metal deposits in it and the fluid was red as it should be and had no burnt smell to it. I changed the governor solenoid, pressure solenoid and filter. Also changed the speed sensor on the transmission. I put new atf-iv fluid that is recommended for it and it shifted better but still would not shift out of first gear unless I let off the throttle around 2100 rpm and it will shift normally through the rest of the gears. If i don't release the throttle it will shift on its own around 3100rpm and continue through the gears. Kickdown works fine and downshifting the selector to 2nd and 1st when slowing down also works. However, taking off with the selector in 1st attempting to manually shift doesn't work unless i release the throttle as well. Getting a CEL for an engine overboost code. Any thoughts on what could be the matter? The transmission doesn't seem to be totally crapped out, but would like some advice.

PS: I believe this is its original transmission at 227k miles.

 

That's your problem it's a diesel, they are pieces of junk. Don't know much about tranny's but mine is doing the same thing. Did you clean the valve body?

 

I haven’t cleaned the valve body. What’s the best way to do that? It didn’t look dirty by visual inspection

 

Taking it out of the tranny taking it apart and cleaning it. That's the only way