rpm change when selecting drive or reverse
#1
#3
It's normal function. When your in park or nuetral your engine has no load on it, so it spins more freely. When you put it in gear, the tranny is in gear and the engine is fighting the drag created by the torque convertor slipping while your foots on the brake pedal, similar to not having the clutch completely depressed on a stick.
Nevermind didn't read carefully, that is wierd.
Nevermind didn't read carefully, that is wierd.
Last edited by flareside4life; 01-12-2007 at 12:33 AM.
#6
You see something most don't recognize or see.
When the transmission selector is moved to a gear it signals the PCM to raise idle so stalling is averted even though you still see a drop in idle, the action still opens the IAC a programmed amount due to the converter loading but not enough to cause heavy creep at a stop sign or light.
The same action happens when A/C and other load sensing is done.
These actions have been incorpoated into the computers for many functions since at least 1985.
Also when cruising, just taping the brake will unlock the converter for a second ot two then lock up again. This is an intended action built in the programs to keep the motor from driving the truck in event panic braking has to be done so total slowing/stopping time is not added to.
When the transmission selector is moved to a gear it signals the PCM to raise idle so stalling is averted even though you still see a drop in idle, the action still opens the IAC a programmed amount due to the converter loading but not enough to cause heavy creep at a stop sign or light.
The same action happens when A/C and other load sensing is done.
These actions have been incorpoated into the computers for many functions since at least 1985.
Also when cruising, just taping the brake will unlock the converter for a second ot two then lock up again. This is an intended action built in the programs to keep the motor from driving the truck in event panic braking has to be done so total slowing/stopping time is not added to.
#7