I have a 2001 GMC Duramax... stock allison transmission. The truck has developed a weird problem where it will not shift into 3rd unless you let off the gas. I have a light +50hp tune on it and I am pretty sure this happened on the stock tune as well. It doesn't happen every time, only occasionally.
So if you go WOT from a stop, the truck will shift into 2nd quickly but when it hits redline in 2nd the RPMs will just stay at redline and the truck stops accelerating... although there is enough fuel/power to keep the RPMs from dropping.
Anyone have any ideas what may be causing this?
Another related issue I had was when towing light loads (a boat) at highway speeds, sometimes the service engine light will go on and the truck just loses all power.. I have to stop it, shut it off and turn it back on to get it to be able to go faster than 20mph or so. You would think I limped the tranny but I am not running that much more HP over stock and the ECU error codes did not mention anything about the tranny. Just wheel speed sensor mismatches, etc.
Any help appreciated.
Thanks,
Mike
So if you go WOT from a stop, the truck will shift into 2nd quickly but when it hits redline in 2nd the RPMs will just stay at redline and the truck stops accelerating... although there is enough fuel/power to keep the RPMs from dropping.
Anyone have any ideas what may be causing this?
Another related issue I had was when towing light loads (a boat) at highway speeds, sometimes the service engine light will go on and the truck just loses all power.. I have to stop it, shut it off and turn it back on to get it to be able to go faster than 20mph or so. You would think I limped the tranny but I am not running that much more HP over stock and the ECU error codes did not mention anything about the tranny. Just wheel speed sensor mismatches, etc.
Any help appreciated.
Thanks,
Mike
