Do Your Trucks Roll Foward?

[gm88]

I have a 1999 c-2500 with the 5.7 and 4l80e and 3.73 rear end. On a flat surface if i put it in "D" and let off the break it rolls foward slowly, if it is on a slight, and i do mean slight, incline it doesnt roll foward at all. I was wondering if your trucks did the same. I m pretty sure that mine used to roll, even up hill, when fully warmed up. (btw it was fully warm when i did all of these roll tests). When its cold it rolls foward no problem, sometimes 5-10 mph on flat ground. just wondering if yours do the same as mine.

 

Thanks

[ColoradoSkiCountry]

Normal.

[old-chevy-dude]

if your vehicle rolls forward on an incline at idle it means the Torque Converter has a very low stall point (take the HEMI cars, the stall point is between 1200 and 1500 rpm) and low gearing (2.82 gearing on the 5.7L cars)

 

what is the 5.3L stall speed? about 1800rpm as far as I can tell but I haven't really hunted for it, and the gears are taller 3.42's right? my Avalanche doesn't roll on the same incline my Hemi car did, taller gears higher stall speed and 3000 more pounds.

[kifels]

every automatic that I have owned does this, be it GM, Ford or my old '88 Honda Accord. this is because the torque converter never completly disengages. thus when letting off the brakes the vehicle will move forward becuse the torque converter is still somewhat engaged. (sorry felt I had to dumb it down a bit, I myself got a but confused about stall points)

[gm88]

thanks, although i may have phrased my original question wrong. All automatics i have driven before (even 34k box trucks w/allison 2400 series) roll foward on flat ground as well. i was wondering how fast yours are going, as mine doesnt seem to roll as fast as it did before, especially on slight inclines (when fully warmed up that is, when cold it always goes pretty good).

[Doug_Scott]

thanks, although i may have phrased my original question wrong. All automatics i have driven before (even 34k box trucks w/allison 2400 series) roll foward on flat ground as well. i was wondering how fast yours are going, as mine doesnt seem to roll as fast as it did before, especially on slight inclines (when fully warmed up that is, when cold it always goes pretty good).

 

Perhaps it is not idling at the same rpm now as it used to? Check air pressures in tires as well. Jack up the vehicle, take the wheels off and push back the pistons in the calipers, and then center the calipers in the slides so the pads aren't touching. Make sure the rear brakes aren't adjusted too tight. Or, just accept that your truck changes slightly every day and will never be the same as it was when new.

As for how fast others idle along in gear on a flat surface, do the math, the TC will eventually go into rotary flow even at idle, once the vehicle hits the max rolling speed on a flat surface, regardless of stall speed.

TC do not "engage" or "disengage". Stall speed is the max speed difference between input and output of the convertor.