Sometimes the engine surges as the trans is downshifting into low right as I am coming to a stop and it occures to me that if one were not expecting an abrupt change in behavior, one would perhaps need to replace someone's front bumper and straighten one's gatehttp://www.dieselplace.com/forum/smileys/Cry.gif

Are you a two foot driver,one Brake, one go peddle ??





Mac

Thats interresting,


Sometimes while at a light full stop, foot on the brake my truck will try to go forward a very small amount. When it first happened I thought someone had tapped me from behind, It startled me for a sec as my http://www.dieselplace.com/forum/smileys/Angry.gif went up, Only then when I turned around I saw the car behind was 10 feet away.


Maybe these D/A's just don't like sitting around, they just want to go


Rob

It's common. Mine did it if you were stitting in a hill and tapped the throttle. Would get a second surge.

hoot, I don't understand the commonality in tapping the throttle sitting still and a surge with foot on brake while still moving

To move forward a bit by just tapping the GO peddle as opposed to press .....

I can do the same ...

Mac

hoot, I don't understand the commonality in tapping the throttle sitting still and a surge with foot on brake while still moving

I think it's a related issue.

Did you have your AC on? I notice that when the AC is on if the rpms drop a little it will surge trying to get the engine back to speed. I almost went through the inlaws garage door once.

I approached the gate very slowly, came to a complete stop, was about to shift into park and the engine surged, and it felt to me that the transmission downshifted at the same time the engine surged, as if there was a long delay in the trasmission final downshift, I would expect it to have already been in low, not downshifting from 2nd to low 3 or 4 seconds after I was completely stopped. I ended up hitting my gate, which from my experience and in my opinion was a very unacceptable thing for a truck to do. It may be common, but I do not consider it "normal". The surge was eough to overcome the amount of brake I was applying at that moment to hold the truck still.

What year truck ??


Was it a one time occurance or can you repeat ??





Mac

2004.5 LLY, can't repeat it, but it has happened 3 times

I have noticed this on my truck as well. It has happened several times. It has always happened before the truck is up to full temp (around 180 degrees). The surge is followed by a rough idle. It feels like the truck is getting either too much or too little fuel. If I shift to N or P it goes right away and idle becomes normal. Come to think about it it feels alot like a manual tranny that isn't getting enough power for the gear its in. I have had it to the dealer three times for this and they have yet to find a problem. It happens once or twice a week and hasn't thrown any codes. I have suggested it could be something electronic in the Allison but have so far been dismissed by GM and the techs. I don't blame any of them. If they can't duplicate the problem its nearly impossible to fix but it sure is pissing me off.

My truck does this as well, it's when I'm slowing to a stop from about 45 mph. When I get close to stopping (15mph?) it does surge a little. It almost feels like the transmission isn't downshifting soon enough and the when it does drop a gear it surges a little. Haven't found it a problem at all (mine may not be as bad as others?). If I slam on the brakes the truck stops... that's what really matters to me!

There was a TCM flash for this in 01 for a delayed downshift .... Also in the TSB is was noted about two foot drivers IIRC ...





Mac Edited by: Mackin