On my last trip back from Texas I had a couple of days where I had a difficult time accelerating. After getting home I have discovered some issues with my exhaust and pacbrake. The pacbrake was not electronically installed correctly. It is supposed to go through the Allison ECU and it doesn't. It goes through the dash switch then back to a throttle idle position switch then to the pacbrake solenoid. When I activate the switch the pacbrake is on all the time the throttle is at, or very near, idle. It should never be on in first gear. Also the transmission should be responding with gear selection in conjunction with the pacbrake. I have ordered necessary parts to complete the wiring and verified that all the connectors are wired correctly. Tomorrow I am taking the ECU to a certified Allison dealer/service center and have the exhaust brake feature enabled. That is going to cost a hundred bucks.

Additionally the weld for the exhaust was poorly welded. It has been leaking past the weld for quite some time. I have removed the section of exhaust and had it fully welded today, forty bucks.

The next thing I noticed was the the marmon clamp at the exhaust side of the turbocharger was extremely loose. Another major exhaust leak. I tightened the clamp to the proper torque.

On the pacbrake there is a large bolt that is supposed to be set so that the closing of the valve is stopped by the bolt and not the valve body. It was nearly and inch from contacting the lever with the butterfly fully closed. I will be adjusting that tomorrow also. One of the warnings from Allison concerns that bolt and that the butterfly could become stuck closed and greatly affect performance.

My questions are:
1. Did the leaks contribute to poor performance?
2. Was the valve intermittently sticking closed?

Our Pac-Brake is also not linked to the transmission. The advantage being, that every time you lift your foot off the throttle, the trans doesn't drop 2 gears (6th to 4th). I find that shifting with the control pad lets me choose how much downshift to use. In traffic conditions I find that the progression of downshifts the trans makes is just about right and I only really have to use the shift pad in hilly terrain. If stopped for any time, I usually just switch off the Pac-brake.
I have not noticed the bolt you mention and should check this is properly adjusted as well. Ours has never stuck on but when first installed the switch to activate the pac-breake was set so that the brake also went on when you applied full throttle. Needless to say this did not work very well.

Bud

The exhaust was leaking in the area of the air intake and so you should check your air cleaner as it was probably sucking in enough of the exhaust to clog the filter up.
I had a leak from the reducer exhaust pipe on the Pac brake cracking open and it choked the intake air filter causing an extreme loss of power.