trying to get 6l80 to stay in lockup in 5th and 6th

[davez28]

hi, looking for some help with my trans tune. i have 2010 silverado 6.2l camed withe a circle d 3200 rpm single disc converter. i cant get the thing to stay in lockup in 5th and 6th gear. when running on the highway it is so anoying and unefficent when starting up a hill at 70mph it comes out of lockup in 6th and reves over 3000rpm. im trying to get it to just downshift to 5th and stay in lockup. i want it to run lockup any time im in 5th or 6th crusing. i have my tcc tables set and to me it looks like it should stay locked. what am i missing?

[lukearmstrong1990]

00.03.03.058 to 00.03.16.705 shows your 6>5 downshift at half throttle. you've asked the converter to unlock for every gear shift, which is advisable as shifting with a locked converter is a bad idea. the converter unlocks, the down shift occurs, converter flares and RPM increases. look at the TCC slip data across the time space I listed. the TCC is applying straight away after the shift. but there is such a great difference between engine and trans input speed its slipping as it applies until the speeds match. you're smoking the clutch. no different to a manual. if you release the clutch with a big difference between engine and trans input RPM it will slip and burn out. that's what you're doing to your lock up. you cant expect a single plate lock up in a heavy car to do what you're asking with a converter that flares like yours. you need to give the converter itself a change to get the impeller and turbine speeds somewhat lose before applying the clutch if you expect it to grab

[davez28]

I understand that and agree with you 100%. Now if I log a 6 to 5 shift without it calling for the converter to unlock in 6th I get a fairly smooth shift without all the flair. I'm trying to get it to call for a down shift rather than unlock the converter in 6th If I manually shifted from 6th to 5th it is smooth as can be. No matter what I put in my TCC lock unlock tables at for 5th and 6th it makes no change when testing and logging. I have went as far as to set 5th and 6 tcc lock at 1mph and unlock to 11mph and it still unlocks the converter in 6th and won't downshift. Any other tables I said I can see the changes made when logging. But for some reason the 5th and 6th TCC tables no matter what I do doesn't seem to change anything almost as though the TCM isn't actually referencing those tables.

I did raise my 6-5 downshift speed and it helped a lot but I'm still getting the 6th unlock occasionally.

[lukearmstrong1990]

I personally set the same values in all patterns including TUTD. normal, pattern A, pattern B and TUTD tables are all identical in my files. this stops me believing it may be swapping strategies. you could try that to rule that out.

try putting pattern B data across the board

[lukearmstrong1990]

your log as far as 5th and 6th TCC unlocking in reference to road speed would make sense for pattern A but not pattern B

[davez28]

I have normal and pattern b set. i left pattern A alone because its my tow/haul mode. i can try setting patter A too but it wont work for me anyways because i need the tow/haul mode

[davez28]

this is where im at now. still unlocks 5 and 6 sometimes. got the lock up slip under a lot better control though

[lukearmstrong1990]

Im under the impression of the following.

using 00.02.22.352 (point A) and 00.03.31.764 (point B) as reference in the log.



point A 6>5 downshift 50% throttle, 2100RPM and 101km/h speed.


referencing the pattern B apply/release table for 5th. it "should" be locked at anything above 18km/h at 50% throttle and not release until 2km/h
referencing the patter A apply/release table for 5th. it "should" be locked at anything above 78km/h at 50% throttle and not release until 73km/h


point B 6>5 downshift 42% throttle, 2640RPM and 78km/h speed.

referencing the pattern B apply/release table for 5th. it "should" be locked at anything above 18km/h at 42% throttle and not release until 2km/h

referencing the patter A apply/release table for 5th. it "should" be locked at anything above 78km/h at 42% throttle and not release until 73km/h


point A referencing both patterns is miles from unlocking the TCC on 6>5 shift
point B referencing pattern B shouldn't unlock the TCC but referencing pattern A its right on the cusp of unlocking pre requisites given it will unlock for a split second to allow the shift anyway.

I would copy your B values into A and try again.

[davez28]

OK I read your post a few times. Maybe it's just throwing me off because you're using kmh..lol I think I get what you're saying. But if I set my pattern a to stay locked up that's not gonna do me any good for towing. So if I set the pattern a and it works for my cruising issue what can I do about my tow haul situation? I'm working out of town now so I won't be able to mass with it again till Thursday

[lukearmstrong1990]

I am not sure what tells the trans its towing or not. I haven't researched what it referenced to calculate that and decide what pattern to use.

I'm wondering if your mods and the extra torque the engine is calculating being produced is close enough to the limit that the added load of a crest is just enough to make it think its towing. it seems to me that the PCM is referencing pattern A at the times your 6>5 shift unlocks the TCC and flares to 3000 ish RPM.
towing you'll want the TCC locked as much as possible. a high stall and towing don't really go hand in hand. horses for courses and mods for suited application.

[davez28]

It has a tow/haul button on the shifter. When I'm logging the mode with two haul off it shows mode normal.. with t/h on the scanner shows it's in pattern A..

I plan on keeping it unlocked most of the time towing. I have a big enough trans cooler on it to keep my temps down.. I don't tow a lot or I would have a different truck but sometimes I need to.

[lukearmstrong1990]

ok, I understand that.

speaking with software engineers they say quite often there are things in the background of software that we cant see and the addresses for the edits we apply when converter back to hex are not always correct. I would copy the data over and see if your problem still persists simply to rule it out.

unlocked towing with a high stall converter, man that's crazy regardless of trans cooling system

[davez28]

ok, I understand that.

speaking with software engineers they say quite often there are things in the background of software that we cant see and the addresses for the edits we apply when converter back to hex are not always correct. I would copy the data over and see if your problem still persists simply to rule it out.

unlocked towing with a high stall converter, man that's crazy regardless of trans cooling system

Idk..everyone else tells me I have to run it unlocked towing or I'll slip the converter

Pulling a 10k trailer unlocked my trans temp doesn't get over 190 on a hot day so as long as i can manage the heat it shouldn't hurt the trans

The stall is 3000-3200 but it's not a real sloppy stall..

[davez28]

I'll let it lock at very low tps some

[lukearmstrong1990]

I guess there's 2 ways to interpret that.

running it unlocked will avoid the TCC trying to engage with a large variance between engine RPM and trans input RPM. the extra weight will let the converter flare more. applying the TCC with large slip will "slip" or burn out the TCC.

running it unlocked will also "slip" the actual converter or it will never let the converter get close to the point of sub 100RPM slip with the extra weight. a slipping fluid coupling generates significant amounts of heat and can damage the oil itself. converter outlet oil is the hottest, fluid temp is typically measured in the pan after its been returned via the cooler. suitable fluid temps in the pan doesn't guarantee that the fluid is not over its designed operating temps when it leaves the converter.

stall speed is mathematically exponential to both torque and weight. make more torque stall speed increases or add more weight and stall speed increases. a 3200 stall for a N/A 6.0 will turn into a 4800 stall if you add some boost to the same 6.0

I would use the scanner and gather as much data as possible. I would think getting moving unocked in 1>2>3 and gaining some road speed, coming back on the throttle to engage 4th and the lock up and having the tune so once locked in 4th you can use plenty of throttle without it unlocking would be best for the trans towing. locked up the converter is a fixed coupling with no slip for heat, basically a manual....
unless the fear is that with all the weight the lock up clutch wont physically hold on being single disk.

[davez28]

That's what I'd like to do. I think it will handle lockup better then others have told me. I plan on doing some logging and see what it will handle. Since I turned up my tcc pressure I'm surprised how much load it's holding without slip. So far I have just been shifting it manually at highway speeds when towing so I can keep in a gear it likes per conditions.