1999 International 4700 T444e no power under 50 mph

Sure it’s not a transmission problem you’re having? Count your shifts, it could be starting in second. Same as the engines, those things have way more electronics in them than they need. I’ve seen some weird #### out of the X000 series transmissions. You’d have to have an Allison guy plug into it and see if it’s having a nervous breakdown.

 

The best way we ever found to check the up pipes was to put our hands around them with the motor stone cold and feel for leaks. If the firewall is covered with soot it's probably a problem. To check the charge air cooler itself I had to make two plugs that fit the boots. I found a big piece of schedule 40 pipe that fit inside the boots glued a pair of caps on and drilled a hole in one. I screwed a air fitting in the hole and pressurized it to about 3psi. I used soapy water in a spray bottle to look for leaks. I hope you figure it out. I did replace my trans once.

 

If it starts in first but locks the converter early it would act like that too. Be lazy everywhere until it was revved up enough to deal with the load without torque multiplication from the converter. I’d get it plugged in. The one up the road did that. Sometimes it locked the converter as soon as the truck moved, or it locked it the instant it shifted.