A friend bought a new 09 4WD CC 1-ton dually and had a different set of tires he wanted to run, so I changed the revs/mile in the ecm tune (8594 OS). Now when towing it seems to lock/un-lock the converter in fifth gear (60-62 mph), worse when going up a slight incline. He's in tow/haul, at about 1750 rpms and then jumps to 2250 rpms, then back, and so on. The rpm jump is not enough to be a downshift to fourth gear so I'm guessing it's the converter. It does it in tow/haul and regular mode, but it'd be in sixth gear when it does it in regular mode, not in tow/haul.
It started immediately after I changed the revs/mile. The 09 tcm's are not tuneable yet through EFI Live, so it may be that the revs per mile change in the ecm is confusing the tcm. I have switched just the ecm revs before on other older 6 speed trucks and never had this issue. I also shut off the egr, otherwise I made no tuning changes, the truck is still completely stock with dpf, etc. I don't see how shutting off the egr could do this, but it's possible. I tuned another 09 for a friend and shut his egr off also, and his is fine, no issues. We did not change the speedo though.
We'll put it back when he can get the truck back to my area, just wondered if anyone else had this issue with an 09.
Jody
It started immediately after I changed the revs/mile. The 09 tcm's are not tuneable yet through EFI Live, so it may be that the revs per mile change in the ecm is confusing the tcm. I have switched just the ecm revs before on other older 6 speed trucks and never had this issue. I also shut off the egr, otherwise I made no tuning changes, the truck is still completely stock with dpf, etc. I don't see how shutting off the egr could do this, but it's possible. I tuned another 09 for a friend and shut his egr off also, and his is fine, no issues. We did not change the speedo though.
We'll put it back when he can get the truck back to my area, just wondered if anyone else had this issue with an 09.
Jody