So i was tuning a lbz truck today and it had 40 in tires on it. went through the process of changing the info so that it would be right. I got it dead on but problem is that as soon as the speedometer would get over 65 mph it would just drop to zero. then when we slowed down once we got to 25 it would pick it back up and then start to work again till 65 again. i thought that maybe the cluster was going bad but i reset his speedometer back to what it was when he showed up and we ran it to 100mph no problem never kick off or anything. has anybody else had this problem and if so have you been able to fix it. i have done tons of truck none with tires quite this big but never ran into this problem. thanks for reading hope you can help.