ZF8 TCM no shift mode

[xennex]

I have read the TCM from my 2024 Wrangler AT.

Tables are all there, but there's no logging of the shift mode or similar so whatever shift pattern is in use is a matter of guesswork. Also no driver type, aggression, shift type.

Best course of action? Open a ticket?

[DodgeBoy_8HP]

Yes.

Share a log and tune.

[james1595]

May have to use the beta scanner to log

[xennex]

I opened a ticket and support has added the PIDs for the logging. Now have 'Trans Shift Mode', 'Trans Drive Mode', 'Trans Shift Range Select', 'Trans Shift Situation', 'Clutch Shift Type', 'Shift ID', 'TCC Pattern', 'TCC Type', 'Driver Type', 'Aggression Counter', 'Aggression Blend', 'Aggression Category Low/High'.

The 'Aggression Counter' to 'Driver Type' using the 30003 Shift Pattern Driver Type Mapping makes sense. As does the 'Driver Type' to 'Aggression Category Low' and 'Aggression Category High' using 30002 Shift Pattern Aggression Mapping. So I can tell the aggression 0-5 now.

'Drive Mode' is Normal / Sand / Low.

'Shift Mode' is 0 (normal), 2 (manual shifting) or 128 (4LO).

Have not worked out much past that. Some of the terminology does not quite match up between the tables, logging and forum posts, so I'll have to work that out myself.

Probably I will need to set some of the shift patterns to a fixed gear so I can definitively tell which are in use.

[LilSick]

Some of the terminology does not quite match up between the tables, logging and forum posts, so I'll have to work that out myself.

Probably I will need to set some of the shift patterns to a fixed gear so I can definitively tell which are in use.

shift id tells you which pattern

that, along with clutch shift type, are all you need to start making changes

what is it (the trans) doing that you do not want it to do?

or what do you want it to do that it is not doing?

[xennex]

Thank you.

Shift ID starts at 0, increasing to 3 under light acceleration. Braking to a stop is comes down to 0 again. Mild acceleration is 4. Heavy acceleration is 8. Note that aggression counter is 0 and aggression blend is 0% for most of that so the shift ID is not being set from the aggression.

Clutch shift type is normal, occasionally going to Perf briefly. Not related to engine load or throttle. Need to test that more.

The problem that I wish to address is that in 4LO and high load (ie a very steep hill) the engine bogs down and gets worse as you give it more throttle.

My understanding is that when not in aggression based patterns the the TCM uses the patterns under 4WD Low. When I then look at the Shift Pattern Mapping they are mapped to the same pattern number, and then the pattern looks like this. Which would give the bogging characteristics I describe because the shift rpm lowers with increasing throttle.

4lo.png

26050.png

I'm pretty sure this is correct because out of all the shift patterns there are only 3 which have 1->2 and 2->1 set to 0 : 41,50,51. 4LO starts in 2nd gear so that matches the table. Not sure if pattern 41 is used. It's like junk DNA then?

My questions would be
- how do I tell when the TCM switches from aggression based patterns to something else?
- when it lists two patterns for 4WD Lo, how are they used? Like the aggression patterns based on acceleration - #50 normally and then #51 under increased acceleration?

2024tcm.hpt

Yes, I probably just need to make a change in the pattern and confirm that it happens. But 4LO up a steep hill is hard to replicate short of driving 100 miles to an off road area.