mdaniel

I'm reviewing a log of a recent run. Where can I find which gear the transmission is in? This is a 4L60.

If I close out the log file I'm able to add (right-click and then "Insert") the gear PID, however, once I open my log back up the gear PID is gone.

WTF. Any ideas what I'm doing wrong?

Thanks

Chris Stewart

It's because when you logged it, the PID wasn't in the config so it wasn't recorded.

tblu92

You have to add the PID for "current gear" to be able to have it recorded
looking at your data log--you went 122 MPH so my guess is that you were in 4th gear--Depends on your rear gear ratio and how far you went to hit 122----With a 4l60 it is easy simply to count the shofts as you increase speed

mdaniel

Yeah - that was the problem - I hadn't added the pid before I started logging.
I lost 3/4 gears in the trans on that pull.
It's a 3:42 gear.

tblu92

The 3-4 clutch pack is always the 1st to go as it's the weakest

romandian

would it make sense to increase the pressure for that shift?

tblu92

No often more pressure will make it worse-----I've had the best results with weak transmissions by lowering the shift times 1st to like .20
and then by lowering the "force motor current" tables----- The FMC tables command how fast the solenoids snap----The larger the number the slower the shift--The table is scaled by trans temperature and by trans pressure----I typically will SUBTRACT like 15% in the FMC table from just past 0% all the way to the end (like 95 PSI) this will create quick crisp shifts--See if that helps--If it does not---most likely it's bad news---

enoniam

The tranny controls pressure by the force motor current. Lower current = higher pressure. Therefore you are indeed increasing pressure by changing the force motor current table as you describe.

tblu92

Well I believe the trans pressure are controlled by the "base trans pressures per gear" tables----They are scaled by engine TQ---as the TQ goes up so does the pressure----At cruising speeds the pressure is low--less than 20 psi---at WOT the most it can command is 90 PSI--
The FMC table dictates how quickly the solenoids snap-- and do not alter pressure per say but a quick solenoid time will allow the pressure to ramp up faster----The FMC table is similar to the PWM table for the TCC---- The stock TCC solenoid snaps very slow using a commanded slow 10% of max value---Most all tuners will set that number to like 90% of max value which makes the TCC shift firmly--The TCC PRESSURE is not changed by altering the PWM tables--same as the FMC tables for the trans gear shifting--

enoniam

What I mean regarding what is controlling the trans pressure is what THING is physically able to adjust the pressure - and that isn't a table. That THING is the Pressure Control Solenoid and it bleeds off hydraulic pressure based upon how much Force Motor Current is going through it which sets the pressure in the Actuator Feed Limit hydraulic circuits of the valve body. The Pressure Control Solenoid is set up to be closed at zero current so that if the electrical circuit feeding it is broken and unable to pass current into the solenoid you will have full pressure which will give harsh shifts, but at least you will get shifts. The Force Motor Current itself doesn't control how quickly the shifting solenoids snap but does affect how quickly the valves controlled by those solenoids move. The Pulse Width Modulation solenoid is a secondary pressure control THING that only affects torque converter lockup. It indeed is a pressure control item in that pressure is what causes the converter to lock, both how quickly and how firmly.

The Force Motor Current table that you are tweaking is simply the translation between desired Actuator Feed Limit Pressure and how much current is required to achieve that given the tranny fluid temp. Like it or not, you are indeed changing hydraulic pressure as THAT AND ONLY THAT is what automatic transmission clutches respond to and in many cases affects how quickly valves react. Electrical inputs into the solenoids based upon lookup tables that you are tweaking are but the means to control the hydraulic pressures. You are getting the results that you want but not for the reasons that you state.