ok... have a check engine light for P0740 torque converter open circuit. I've changed fluid and filters, and light goes away after 100 miles or so. Then comes back. I cleared the code, and it stays gone as long as I stay below about 50mph. yesterday I did a little towing, and turned off the o/d, and heard some funny noises just before the shift points for 1st, 2nd, and 3rd gears. I turn the o/d back on and the noises go away. once everything is at op temp, I turn the o/d off again and there are no noises in shifting. I drive the 40 miles or so in city traffic, and then hear the electric fan running, but the water temp is well below where it would normally activate the fan. I check the trans fluid level and it is about 1qt over filled and very thin. also there is a slight smell of burnt tranny fluid or clutch, not sure which. parked for about 10 mins the fan turns off and the smell has long gone away. I dont have the time or money to take it in to a shop, or just randomly replace the converter or selenoid. anyone have some tips or directions to diagnosing the failing part?

 

what I've noticed is the CEL won't come on until it is plenty warmed up and doing 50 or so. also today I just tested to make sure it is locking up the TCC. I have an idea, that kinda makes sense, but not sure yet. my idea is that when it gets hot, the fluid is thinner. I think there is a partial blockage in either a cooling line, or the cooler itself. this would cause the pump to create a bit of a vacuum at higher speeds, thus not getting enough pressure to keep the TCC locked up. this is my idea at least until I learn some more... open for ideas

 

If MasterTech doesn't chime in here soon, shoot him a pm, he's the transmission expert here.

 

I've been reading that there is an anti drain back valve on a cooling line, but I don't see where it could be... I'm starting to think there isn't one on this tranny, and they were talking about the 46 tranny.

 

Yeah they changed a couple of things with the introduction of the 4.7 engine in 2000, so I couldn't really tell you.

 

Are there any other codes along with the P0740? My guess at this time would be the solenoid pack. But to replace that, the valve body would need to be removed. Here some information on the code. It also does help if you have a scanner. No there is no drain back valve on the 45/545RFE transmission. That's because this transmission has a two stage pump.

TEST ACTION APPLICABILITY
2 With the DRBIIIt, read transmission DTC’s
Is the DTC P0750 present?
All
Yes ! Refer to the Transmission category and perform the appropriate
symptom.
Perform (NGC) 45RFE/545RFE TRANSMISSION VERIFICATION
TEST - VER 1.
No ! Go To 3
3 With the DRBIIIt, Read and RECORD ALL Transmission DTC’s. After recording
DTC’s, erase DTC’s.
Drive the vehicle until the transmission temperature is at least 43°C or 110°F.
Perform the following steps 3 times.
Drive the vehicle at 80 km/h or 50 MPH.
Allow 4th gear to engage for at least 10 seconds.
Close the Throttle.
Tip back into the throttle until the TPS angle is between 25 and 29 degrees.
NOTE: If the throttle angle goes over 30 degrees, you must close the throttle
and try again.
Did the TCC engage during any of the attempts, Engine speed approximately equal
to input speed?
All
Yes ! Go To 4
No ! Go To 5
4 The conditions necessary to set this DTC are not present at this time. Using the
schematics as a guide, inspect the wiring and connectors specific to this circuit.
Wiggle the wires while checking for shorts and open circuits.
Using the schematics as a guide, inspect the wiring and connectors specific to this
circuit.
Wiggle the wires while checking for shorts and open circuits.
With the DRBIIIt, check the EATX EVENT DATA to help identify the conditions in
which the DTC was set.
Were there any problems found?
All
Yes ! Repair as necessary.
Perform (NGC) 45RFE/545RFE TRANSMISSION VERIFICATION
TEST - VER 1.
No ! Test Complete.
5 With the DRBIIIt, check for other transmission DTC’s.
Are codes P1775 and P0841 present also?
All
Yes ! Replace the Transmission Solenoid/TRS Assembly per the Service
Information.
Perform (NGC) 45RFE/545RFE TRANSMISSION VERIFICATION
TEST - VER 1.
No ! Go To 6
6 If there are no possible causes remaining, view repair. All
Repair
Repair internal transmission. Inspect the Oil Pump per the
Service Information and repair as necessary. If no problems are
found in the Oil Pump, replace the Transmission Solenoid/TRS
Assembly. Replace the Torque Converter in either case.
Perform (NGC) 45RFE/545RFE TRANSMISSION VERIFICATION

 

Also check the side plate on the valve body too. Sometimes the screw heads will snap off.

 

I don't have the DRBIIIt scanner, but that is the only code that shows up with the ODB scanner. the three key turn trick shows the generic P0700. for dropping the valve body plate, happen to have any diagrams to show which bolts and possibly some torque specs for re-installing? (crossing fingers for a link to a diy slide show or video lol)

 

Just take it to a transmission shop. They'll hook their computer up to it, take it for a 5 min spin and come back and tell you what's wrong. In my case, it was $600 for a new Torque Converter.

SJ02

 

I'll take it to a shop to scan it, but I'll probably do the work myself... depending on the amount of expertise needed to fix it.