can't keep steady speed it goes from 65 to 60

The only way to change speed limiting parameters - use DDRS software, but first I pull engine control unit fact. password. Well, I do change of speed limits for owner only, if driver wants to change it I ask him to call owner and if owner wants, I do it.

 

if the mph is hunting up and down like that--the problem could be in the foot pedal---that can be checked out with a handheld and check the other parameters at the same time

 

usually speed limiter hysteresis is 3-5 mph, but there is time of reaction and if truck looses speed too fast it may slow down up to 10 mph.

 

Do you think you have lost power? If not, I would check if they changed the maximum road speed by accident or what ever. Part of a Detroit tune up is to check the injector calibration codes and then see if the ECM has the same codes.

 

I'd find a Detroit Diesel distributor to do the work... way too many Freightliner dealers screw up engine work in my experience.

 

does it do it only on cruise. if so make sure speedometer tone wheel and yoke are tight.