Hey guys,One more question to make me feel better about my rebuild.I have had problems with idle,I have cranked without transmission installed,so question is how much of an rpm drop to expect when driveline is installed.

Hmm.

For an auto, it should be the same drop you get when going from neutral to park or drive. 200 rpm? Maybe someone with an auto can provide that info. Also is the engine fairly stock?

but doesn't the torque converter have some impact??? even in park, the TC is loading the engine at some level.

That's my point. The TC loads the transmission and pulls rpms down in park and drive. Not in neutral.

Park is neutral with a pawl locking the tailshaft. I was thinking that it's shear weight would have an effect...

from N to D I go from 700 to 600ish when cold
750 to 625ish when warm

Quote:

Once it's spinning, it's just a flywheel, the loading would be minimal. Yea, it will take a little HP to keep it turning but I'll bet it takes more power to run the pump in the trans than to keep the tc spinning. IMO.

Am I missing something?
Would the correct answer be zero?
If the ecm has a target idle speed, would the engine not achieve that speed? Regardless of a trans being bolted to it or not?
Plus or minus a few rpm, of course.

You need to install a trans before you try dialing in a tune.

I'm not sure how much of an rpm drop there will be, but Pete is right, it will search for the desired idle that is set in the tune. It will open and close the IAC as necessary to find that idle, but the fueling won't change to find the desired idle. This could cause a surging idle.

Install a trans, reset the IAC, and see how it is. If it isn't right, you might need to open or close the throttle blades by the adjustment screw to achieve the proper IAC counts. Sometimes closing the blades some will cause a lower idle, sometimes opening the blades some will cause the idle rpm to stay the same but cause a smoother idle. It all depends on your combo and where the IAC steps are.

Get a trans in there first, then begin tuning the idle. Quit worrying about the rebuild, if it runs good but just won't idle exactly as you want, the rebuild is fine and something small or some small tuning adjustments are all that will be needed to get the idle right.