It is nice to have a heavy truck

[Stumper]

Carl, That was my presumption.

 

[DTW902]

Pretty sure diesels don't have vacuum modulators .

Sure some have them, if the diesel has a vacuum pump. Look at a ford truck someday with a diesel. I would guess that Justins problem has nothing to do with vacuum on his truck. Justin call around and see if there is a Allison dealer near you. They are not bad on price even if a rebuild is required. Less than a lot of cars and pickups.