I am running a SD '730 ECM. I am wondering how to prevent the TCC from un-locking while I am off the throttle at 50-55 mph. It is getting annoying to me.

I currently have the TCC engage set at 50 mph

I currently have the dis-engage set at 44 mph. It was set to 48 mph but I just changed it thinking that was too close to the engage speed of 50.

Still unlocks when i let off the throttle at 50-55 mph and I step back on the gas. It does re-engage very soon but why should it even dis-engage at all? If I am at higher speeds then it will not do this (above 60 mph).
Seems to me this would be hard on the convertor, unlocking and locking alot in traffic.

I have even went into the switches and un-checked "Unlock TCC in decel fuel c/o". It didn't make much differance. The TCC still unlockes briefly and locks again.

Any ideas?

 

This was covered very recently, past two weeks? There are two
values that are TPS% thresholds that when crossed will
cause the TCC to unlock.

If this doesn't work someone (past 2 months) posted a
patch to eliminate this 'feature'.

RBob.

 

RBob,

Thanks but that's Greek to me. LOL.

If it's not defined in TC's $8D I have a VERY hard time understanding it.

I checked out the other posts before and they were still playing with the code. I hate not understanding that stuff. LOL.

Anyway, it seems that TC's latest $8D MIGHT have the same 3 bit change as described here:
https://www.thirdgen.org/techbb2/sho...ght=tcc+unlock

There is a switch called "Unlock TCC in decel fuel c/o". I tried that and the TCC still unlocks on me while lifting off the gas at highway speeds.

 

No simple way to change this condition?

Well, maybe someone can tell me what the switch called "Unlock TCC in decel fuel c/o" in $8D does? '730 SD computer of course.

 

Yes there is a simple way. RBob pointed you to it. At L8318, change it to 0. What that line does is unlock the TCC when the TPS% reaches 3%. Setting it to 0% should solve the problem but if it doesn't you'll have to do the patch described in the link you gave. The switch you mention just turns off TCC if in DFCO but the engine doesn't always go to DFCO when in decel as that has its own parameters.

 

I have ONLY used TC to edit my BIN. I am not sure what you mean by changing L8318 to 0. Educate me please, what software will show me this location in the program?

 

RBob,

What is are the addresses to do the same thing on a 7747? I have a 4+3 and would like the OD to not unlock when lift off the throttle at 80mph. Thanks for your help.





















:hail: :hail: :hail:

 

I guess you could use PP2 but you would then have to upgrade or disable the checksum. You would use edit buffer once the buffer were filled with the bin you want. The line to look at would be 0318 if the start of device were set to 0000. It should have a 03 in it and it needs to be changed to 00. Winbin will also do this if you go to where it says HEX and hit populate chart. It might even update the checksum automatically but I don't know if it's accurate.

 

Set these three locations to 0:

$567
$568
$569

And to disable DFCO unlock set bit 2 ($04) of $007 to a 0.
(IE: if $007 = $24, set it to $20)

(The addresses as shown are the physical EPROM addresses).

RBob.

 

RBob,

Thanks. That's great. Do I need to set all of them to 0 in order to avoid the unlock at decel or just the one for DFCO unlock?

 

Decel unlock and DFCO unlock are two different things. Although either will unlock the TCC.

Decel unlock unlocks the TCC whenever the TPS falls below a threshold. (the first three values above).

DFCO unlock will unlock the TCC whenever DFCO is active. A throttle lift at 80 mph in gear will most likely invoke DFCO. Resetting bit 2 at $007 will disable the TCC unlock whenever in DFCO (decel fuel cut off).

RBob.

 

RBob,

Thanks so much. That's excellent. While I have you on the line, are you aware of any way I could recreate the AVG/INSTANT MPG display on my Vette dashboard? Once I swapped the stock ECM for a 7747 I lost that function.

 

just to add a few things, tho i'm late to the party.

I tried disabling the "DFCO TCC unlock" and it didn't help.

that's why I did the hack referred to above.

I didn't realize that there was the TPS thresholds which the TCC unlocks below.

I will have to play with those...

 

For the 8746
Set these three locations to 0:

$4B9
$4BA
$4BB

And to disable DFCO unlock set bit 1 ($02) of $005 to a 0.
(IE: if $005 = $23, set it to $21)

(The addresses as shown are the physical EPROM addresses).

JPrevost. (Thanks RBob for the hack, this makes things so easy).

 

In regard to the original post, just ask TC to add the 4 constants that were mentioned in Rbob's post. They are allready in the latest $6E and $32B tdf files. The min load limit for TCC lock is the only parameter to set=0%tps, to fix your problem.

The stock ARAP had the high speed load limit set to 0%tps, so it would not unlock when you back off the gas (when above the threshold). My stock GM had it set to 3.9%. I think they did not want a big load applied to the TCC when you back off, so they unlock the clutch.

HTH

 

Why not just edit your own tdf file with the TDFEditor software he has?