ok, my truck just got a new allison put in it. it has a 6 month warranty. it shifts fine when its cold, but when trans temp heats up it tends to grind out of gears, when i say grind, i mean when you are going 65 miles an hour on the interstate and you hit the breaks mildly to slow down to get off at an exit i can feel it in my braking that the truck grinds when it downshifts. what could cause this, how do you prevent it? ive driven this truck about 700 miles on the new tranny, no racing, no beating, no bullchit. Are me and the allison just not meant to be???

take it back as soon as possible. grinding is never good

Sounds like your hyraboost is making noise.

Sounds like your hyraboost is making noise.
hyraboost, i have never heard of this Mike. Can you elaborate a little. I'm scared to death I'm gonna be without a truck for another week or two. Any point in the right direction would be greatly appreciated. Also, I don't understand why it would all the sudden start grinding like this. I can feel it in my foot when my foot is on the brake slowing the truck down:D This doesnt' seem normal, in fact, this is what my truck was doing when the tranny got so bad I had to replace it.