Loosing 4th once converter is locked

[Taz]

Hello Ian,

The following should be taken as general information … bearing in mind my “so called” area of expertise is Gen III conversions - not Gen IV setups. The 4L65 you have is very similar to Gen III variants - with the exception of the addition of an ISS.

The below information is from GM service manuals of North American produced trucks (my primary source of parts and harnesses) - your Holden produced vehicle may vary.

The TFP (transmission fluid pressure) assembly bolts on the bottom (pan side) of the valve body (usually by 3 long and 2 short bolts). The TFT (transmission fluid temperature) sensor is incorporated into the TFP assembly. The TFT sensor is a “thermistor” - similar to the ECT (engine coolant temperature) sensor.

The TFT sensor has a range of 0 to 5 volts. When the TFT is cold the resistance in the sensor is high, and the voltage is also high. The reverse is also true.

5 volts = -40C (-40F)
0 volts = 151C (304F)

“Hot mode” is triggered at 135C (275F). There are many situations (and DTCs) that inhibit the torque convertor from locking in 4th gear. Generally, only “Hot mode” will inhibit 4th gear itself.

Many transmission DTCs do not illuminate the MIL in the IPC - a scan for any / all stored transmission DTCs would assist in further diagnosis of the problem.

My “instinct” given the diagnostic efforts thus far - is a defective TFP assembly, or a poor / intermittent connection to the TFT sensor - as “zero volts” (or no connection) from the TFT sensor will be interpreted as a “hot” transmission.

Regarding transmission PIDs that may assist in diagnosing the current problems …

Current gear = GM.GEAR (caption is GEAR)
Shift pattern = GM.TSHIFT (caption is TSHIFT)
TCC enable = GM.TCCS (caption is TCCS-TCCEC)
TCC control solenoid = GM.TCCS (caption is TCCS-TCCCSC)


Regards,
Taz

[alian]

Taz, Great information. I have a question though, if the TFT sensor is faulty and is the cause of the tranny going into "hot mode" you would think that the TFT readings while logging would have to spike up above where the readings are. Just trying to get my head arround it.
Cheers Ian

[Taz]

Hello Ian,

As I stated previously, a problem with the TFP / TFT system is only my “instinct” - just a possible option - the only thing you have changed is the transmission itself - the problem may turn out to be something else. Not sure if the transmission temperature PID is actual or calculated, or how an intermittent connection would affect the PID.

I’m basing my “hunch” on the elimination of the 4th gear “Hot mode”, and the subsequent “normal” shifts of the transmission. More diagnostic work is required to eliminate other options - difficult to be more precise from half way around the world.

I have done Gen III conversions for a while now, just getting into the Gen IV. On a couple of Gen IV conversions that I have helped out with, I have observed the transmission shift pattern (when logged) oscillate from Pattern 1 / Hot / Cruise - etc., for no reason known to me. On those vehicles, I set all the shift patterns to the same parameters to “stabilize” the shifts.

Not sure if this phenomena is occurring in your vehicle - until you try and log it. If it is, hopefully a Forum member with more Gen IV experience than I, could answer why this happens - I would certainly like to know.


Regards,
Taz

[alian]

"I have observed the transmission shift pattern (when logged) oscillate from Pattern 1 / Hot / Cruise - etc., for no reason known to me"


Taz were you using Shift pattern = GM.TSHIFT. I am off to Holden to get the original tune today so I can start afresh.
Thanks again for all your help.
Cheers Ian

[alian]

Update!! Holden were unable to overwrite the tune as I already had the latest calibration. So still on the lookout for a std tune for it.
CheersIan

[limited cv8r]

What OS number are you looking for? What year model crewman?

[limited cv8r]

Woops, just looked at your attached tune.I have a few here with the same OS. I have done a compare of them and they are all identical, so I have uploaded this one for you.

[killerbee]

I saw a similar thread on this. Very similar. TFT voltage scaling difference?

[killerbee]

http://www.gm-trucks.com/forums/inde...owtopic=123115

[alian]

Woops, just looked at your attached tune.I have a few here with the same OS. I have done a compare of them and they are all identical, so I have uploaded this one for you.

Many Thanks mate. I have looked at your tune but it has been modified. Do you have the original? Or is the date that every thing was modified (Feb 15, 2007) the date that the standard tunes weas modified?
Cheers Ian

Killerbee, Interesting stuff