|Quoting Cfalk (Reply 3):|
Sounds like the torque converter isn't locking up. Lockup is when the constant slip of the torque converter is eliminated, which effectively acts as overdrive, rather than an actual extra gear.
Cfalk is correct about the Torque Converter Lockup possibility...however it is not an overdrive. The torque converter (TC) is designed to allow a certain amount of "Slip" (input rpm v.s. output rpm). Torque Converter "Lock-Up" is a 1 to 1 ratio and is like fully releasing the clutch on a manual trans. The overdrive gear ratio is only present in the "D" position or 4th gear, with a 4 sp Auto.
|Quoting Muddydwagon (Reply 4):|
I believe in that transmission it is more than likely going to be a vacuum modulator
Negative....Sir. A modulator failure would create a high rpm upshift condition in all gears and not just cruise.
|Quoting CFCUQ (Reply 6):|
The torque convertor clutch sounds like it is not locking up at cruise speed. Several possibilities, the clutch switch may have failed, or there may be a no power to switch problem.
I agree this is most likely a TC
lock up problem, however, the torque converter lock up solenoid obtains power from the same source as other trans.solenoids. Unless the open power circuit is at the trans connector pin for the TC
, and only the TC
the solenoid itself, unlikely diagnosis (but not impossible) and you would have other problems.
Torque Converter lock-up is applied by the ECM (Electronic Control Module) after certain conditions are met. The ECM supplies a ground circuit the TC
solenoid, which engages a "Sprag Clutch" inside the TC
and locks up the converter to a 1 to 1 ratio. Not only does it need power (12v dc) but it needs a ground (neg.) path to the ECM.
The ECM will apply TC
lock up once certain parameters are met. I can list a few of the items that the ECM considers to determine lock up.
1. Engine Temp
2. Throttle position
3. Engine Vacuum
4. Engine RPM
5. Brake application
6. Road speed
7. "Check Engine" light is on.
If the ECM is getting bad info on any of these items, no lock up.
You need to drive the vehicle with a Scan Tool that displays live ECM data to find out WTF. If the scanner shows the ECM is commanding lock up and it's not happening, then as CFCUQ suggested, check for power AND
ground for the TC
at the ECM. If power and ground circuits are good, most likely the TC
lockup solenoid or TC
sprag are bad.
[Edited 2006-01-14 06:30:39]
[Edited 2006-01-14 06:31:12]
474218, Carl, You will be missed.