Hey guys, I’ll try and give as much details as I can. 2004 Columbia. 4.0 42re trans. I got a little muddy water in the trans the other week. I’m a shop foreman for a trucking company, so I drove it straight to my shop and drained it all out. Had no problems at this point. All of our equipment is for heavy duty trucks so I couldn’t flush it all the way. So I filled and drained until it looked normal and changed the filter. Ran fine for a couple days and now it’s acting up.
When acelerating from a stop. It will not shift out of first until I hit 4200-5000 rpms. When it does shift it’s smooth. When it’s in the next gear (it feels like 3rd) I have no kickdown. You floor it and it just gradually goes. Downshifting is smooth. Here is what I have checked/done.
-dropped pan for a 4th time, no chunks of clutch packs or metal
-used professional code reader, 0 codes active or inactive on anything
-checked all fuses and relays, replaced the all for the hell of it
-shifting into neutral then back to drive doesn’t seem to help
-checked the kickdown cable or I think it’s called the throttle position cable
-visually inspected wires and such to the trans.
-trans cooler is not hooked up

It’s not overheating
Using 1st or 2nd gear doesn’t help.

Im kind of lost where to look next, it feels like it’s maybe a issue with the tcm putting it into limp mode or something. It doesn’t feel mechanical.