for you guys with a 700r4...

[eagle mark]

I knew the transmission didn't since its electronically controlled. But I was wondering how the controller knew when the engine was loaded and a downshift was needed.
I figured there might be a vacuum reference that the controller read.

Otherwise I guess its a combination of throttle position sensor position and rpm.

An 05 has no vac reference, as its a 4L60E. But the 700 didn't either. A th400 does though.

Although theres no vacuum reference from 4l60E and 4l80E trans... they always know vacuum of engine through PCM MAP reading. Everything has a setting for shift MPH, vs Load, vs RPM, vs TPS position. It's amazing how preprogrammed these are, where a 700R4 the only thing from ECM was TCC lockup at MPH.

 

[Deuling]

Yup. Biddy of mine killed 2 brand new trannys right after another cuz he didnt adjust it right.

 

[K85 Octane]

don't drive it without at properly functioning TV cable

EDIT: need to refresh threads more often

 

[Fordum]

Aha. I forgot about the MAP sensor. The PCM could make a pretty good guess about the load on the engine by watching the RPMs and the TPS. If the RPMs start dropping without the TPS changing, or if the throttle opens without the correct increase of RPM, then it indicates the engine is lugging and needs a lower gear.

Which was the function of the vacuum modulator on the old transmissions.

But, the MAP tells the PCM what the manifold vacuum is, so it can put all the pieces together to tell the amount of load on the engine.

Huh, never made the connection........

 

[Fordum]

don't drive it without at properly functioning TV cable

EDIT: need to refresh threads more often

Tell me about it. I suddenly realized that the MAP sensor was the vacuum reference, posted a comment about it, and as soon as it went in, I saw the post from Eagle Mark saying the exact same thing.

 

[454Sub]

Yea its the TV, we didnt drive it, just put it in gear to see if it would even kick, which it does. But I was looking it over and seen the cable dangling and was like . No biggie, ifs its toast I have a 700 Iv been kicking around the garage with the newer pump and all the updated bands and the corvette servo. Im half tempted to toss it in the Sub, but I have a burned up 4L80E with all the wiring and computer im stepping over to get to stuff here as well.

 

[eagle mark]

Although the vacuum/MAP reference is always there with PCM, the E tranny is more MPH controlled, then TPS%. Changing tires or gears can ruin a good driving rig. To give an example when re-flashing a e tranny PCM for tire size change there are 400 to 600 MPH changes in all the tables...

 

[Blue85]

Alright, I just went and looked at a truck and the TV cable was broken, I can't remember anymore but will it lose reverse? It has forward gears but we didn't drive it, buddy of mine just bought it and we looked at it tonight

It must have been stuck partway out. With the cable fully relaxed (i.e. closed throttle) the tranny will shift very soft at very low rpm. It will totally slip through shifts at high throttle, possibly burning up after just a few shifts. So you are lucky.

Get it connected again, adjust it right and everything may be fine. The TV will not affect reverse, except that line pressure may be low. If you need to move the vehicle to work on it, it's OK to idle it into the garage or whatever, but not to drive it down the street.