2008 6.0 4l70e out of silverado hd1500. swapped into 48 international.

i got the engine ,trans ecm ,tcm . all from the same truck 2008 silverado . used a howell wiring harness. i took out the vats. changed the tire size and gears. but the trans will not shift properly. it up shifts very quickly. and wont down shift at all. it not setting any codes. it will pull all 4 gears. the only down shift is if you do it manually. is there something i need to change in the tune for the swap. after i changed the the tires and gear the speed out put on the vcm scanner is correct . but the trans still shifts the same..it has a 40 tooth output speed sensor . but im not sure if the input turbin speed sensor is reading . i made sure the wiring harness is for the 4l70e . and it is.

any help someone? ive traced all the speed sensor wires it all looks right and ohms out good. i scanned it, it has input and output speed. ive changed shift charts .with no change at all in shifts. powers and grounds are all good.

If I had to guess, I'd say it's an issue with it not receiving the correct vehicle speed or input speed on the trans. Can you see in the scanner where it's commanding a downshift? Are you able to command it to downshift in the VCM controls? Have you checked the solenoids to make sure they are still good?

If you are getting quick shifts that aren't at the mph you have them set to in the tune, I really think it is an issue with speed input.

thank for the info. It was because of speed sensors. it has a jeep transfer case .so the speed out put is in the adapter. i reflashed the computer from a 4wd to a 2wd. and it fixed the issue. because the 4wd has 3 sensor in the t-case is there a way to pin it different ?