04' Rm 2500 4x4 Cummins
This seems to be a common problem.....
Speedo is fine in morning when cold, heats up and it starts
bouncing around, can't use cruise, if bouncing at idle,
it can stall engine because the trans starts out in a higher gear.
ABS and BRake light on.
1- replaced VSS on top of reardiff, no luck
2- replaced Trans speed sensor, no luck
3-Cleaned all major grounds
3- Have read it could be moisture in ABS module connector or bad ground at ABS

Any other ideas would be appreciated !

Had a shop scan it and it is showing a
'open circut" in the ABS module.
Speedo was not acting up when it was scanned.

Can the ABS module itself cause the transmission
to change shift points when speedo is bouncing?

It did it last night~7pm at a stop sign, I shifted manually
from 1st and it shifted fine.
It didn't act up when air temp cooled off so
the issue is definitly temperature related.