Pulsation of the truck comming to stop or moving

[dersark]

My 04 truck ( duramax + alison) has about 41000 mils with no problem. Recently I noticed when I put the transmission in drive without pressing on acceletor truck moves forward with pulsation. Same thing happens when comes to stop. If I brake or accelerate little bit faster I do not get that. Transmission has regular services with filter change. The pulsation became very apparent when I put the camper on it. Any idea, please. Thanks.

[Harley Bob]

Thought I had responded to your thread, but apparently my original message didn't get posted. Since I'm a new member, maybe the registration hadn't gotten completed.

Anyway, I have a '02 Durmax/Allison. The same problem you described occurs with my truck. Originally thought it might be brakes dragging or a U-joint in the drive shaft. Believe it started occurring about 3 or 4 years ago, hasn't gotten any worse, but is annoying when it occurs. Usually can make it happen by just letting the truck creep in drive while slowing to a stop. It seems to occur only when the drive shaft is turning ever so slowly!! Can't say I've noticed any difference whether empty, or towing my 13K lb toy hauler. Doesn't seem to be bearings or gears either since there is no howling or other symptoms above creep speed.

Have just completed an 11K mile trip through the Atlantic Provinces and New England. Upon returning, I visited my local chevy dealer to get the tranny flushed. While in the shop, I spoke with the technician, and he drove the truck and experienced the problem. He thought it had to do with the Allison torque convertor, when the transmission is in the lowest gear. He didn't think it was a problem, but who knows! It may be worthwhile to check an Allison forum, or Allison service letters to see if they have any information.

[killerbee]

It is fuel pressure/pulse related. it can be observed by logging with EFI live

[carco]

Mine pulses a little when moving slow ie. stopping or slowing rolling @ a stop or parking lot with no accel pedal pressure. I feel it is engine related, the tach nor engine are dead steady when this occurs. Maybe a fuel pressure issue? Maybe like Killerbee suggests. bob.............