Anyone with a Isuzu, GMC flat nosed W truck please help! My exhaust brake on my 1987 GMC W45042 with 3.9lt turbo Isuzu diesel is not working I think. How can I check it? I can't move it by hand so is it stuck? Also my econo light is flashing and the trans won't go any higher then 2nd. It worked fine until I hit the econo switch. Anyone ever had this problem this thing is driving me bonkers! They said at the dealer it could be the parking brake or the the exhaust brake that could cause all the problems. My parking brake cable is out of the drum so thats not good. The truck has only 124,000 miles on it. The tow bill will be $150 each way and the shop fee of $180 just to look at it.