So I got myself a HP tuners to do my own tune and my brother in-laws truck.
I have the 01 suburban 2500 tow pig and would like to know when it's best or safe to lock up the convertor while not towing and when towing? I've used my Google powers but came up with no good answers. Lock up only when in od ? Locked up when towing above 1st gear and 50 mph ? Thanks !
I think your guiding principle should be that the converter clutch can hold full engine torque but it shouldn't be engaged/disengaged during full engine torque.
As a side note, I have my 6L80 tuned to not engage LU until 4th gear. For a 4l, I’d only want LU in 3&4.
I think it depends on where the shift points are, too. If you set it to lock up when it gets to third and you're at 2700 rpms, locking the TC near the torque peak isn't a good choice. Great for getting torque to the wheels, bad for TC clutches.
I don't know the software, so I don't know what your options are, but if I had the choice I would lock it as you get to OD (when you're likely pulling off the throttle anyway) and then unlock it when you fall below 30 mph. That way it stays locked for most of a highway run, but isn't engaging/disengaging during high torque situations.
Ford did this with many of their E4OD/4R100 transmissions. All of mine would lock the TC as it shifted into 2nd, so the 1-2 shift felt like two separate shifts as TCC would happen about a second after the shift. Of course, that's not necessarily a good thing... how many Fords have the dreaded lockup shudder?
I'd start with a bit more conservative lockup settings (only engage under fairly light throttle, etc.) and drive it a bit and experiment. You'll start to get a feel for when you want it to engage and disengage and when you want it to stay engaged as you go. Different people have different preferences, so it's hard to give a universal rule of thumb.
Thanks guy, I'm not unhappy with it in normal mode, just needed to know when it was ok to lock up in tow mode.
Do you leave it in 3rd when towing, or leave it in overdrive ?
Or does it matter if it's flat ground or hilly ?
What is best for the tranny , if you are more concerned about tranny life and not fuel mileage?
Thanks for the info
I leave it in 3rd with the tow mode on when towing. My local lake is a 15 Mile drive from my home and full of hills. That would be high way 97 for you CMP fans
Does the Suburban not have a tow/haul mode? I would download a truck tune from the website and mimic the factory tow/haul mode tune. Unlock the converter above about 20% throttle and unlock between shifts. Don't get carried away with line pressure either. I see no reason to lock up the converter before 3rd or 4th gear.
The best thing you can do for that 4L80 is put the biggest trans cooler you can find on it.
Patientzero said:Does the Suburban not have a tow/haul mode? I would download a truck tune from the website and mimic the factory tow/haul mode tune. Unlock the converter above about 20% throttle and unlock between shifts. Don't get carried away with line pressure either. I see no reason to lock up the converter before 3rd or 4th gear.
The best thing you can do for that 4L80 is put the biggest trans cooler you can find on it.
Lots of cooling is good, but 20% throttle is MUCH too early to unlock the converter. IMO, in 3rd and 4th, don't unlock it until you're ready to downshift a gear. Running with the converter unlocked when it doesn't need to be plus a trailer on the back is a great way to make a lot of heat very quickly.
In reply to rslifkin :
Hence the cooler. 20% may be early but I'd rather have it unlocked when it doesn't need to be than locked when it shouldn't.
You'd be surprised how little throttle you actually use just cruising around. If you're hitting 20% throttle you probably intend to downshift.
In reply to Patientzero :
I have the biggest cooler that will fit
What is the biggest cooler you can fit and what do y'all recommend? I just tuned a basic rebuilt 4L80 from these guys https://reman-transmission.com/transmission-codes/?code=4L80-E with a thor level 3 converter, want to make sure it stays as cool as can be. RV cooler maybe even?
In reply to timstyler :
It might be best to make your own thread. We don't know what you're driving or where you're mounting the cooler. Figure out where to mount it and then get the biggest one that will physically fit.
I have a 2004 Suburban 2500 that I've been playing around with using EFILive, especially around the transmission tuning. The stock transmission tuning, at least for my 8.1, is very aggressive (much more so than the 6.0 tune), and changed year to year across all of the (few) stock calibrations for Burb 2500s I've been able to find.
At least with the 8.1, the converter has a fairly high stall speed. There is some economy to be gained by locking up earlier at light load and lower speeds - I picked up over 1 mpg around town which doesn't sound like much, but it's a 10% improvement when you're barely gettign 10 mpg city to start with.
Unlike the 4L60, the 4L80 doesn't seem to have any problem running unlocked in 4th (4l60 cuts cooler flow in OD and gets hot if the converter is unlocked)
The 8.1 tune (and if memory serves, the 6.0 tune as well) locks the torque converter in 2nd gear over 93% throttle, and will shift with the converter locked into 3rd and 4th. The converter will also lock in 3rd if you're on the throttle pretty hard, and will stay locked when it eventually goes into 4th. This is usually a pretty abrupt shift.
I would not lock the converter in 1st. I don't think it's even an option in the software.
Locking the converter is fine when towing; it really improves efficiency and reduces trans temps. You just don't want it locking at low engine speeds and lugging the engine at high load, and I personally really don't like the locked shift from 3rd to 4th. It's pretty aggressive and pretty abusive.
There is a switch in the software to allow lockup when shifting. It doesn't do what the internet seems to think based on my testing - the PCM already allows the converter to stay locked regardless. That switch allows the converter to lock at the same time as the upshift if it wasn't locked already and the TCC table for the next gear is commanding lockup. I would recommend not turning this on - let it upshift and then lock up.
The internet also has a lot to say about torque management. Don't get rid of it, and if your maps are allowing shifts with the converter locked, I'd really suggest making the torque reduction even more aggressive than stock at high load. Combine that with slightly higher line pressures and you will get quick, positive shifts with less heat generation.
Something to think about when tuning the converter that took me way too long to wrap my head around: there is no "default TCC off" when shifting into the next gear. The TCC will remain at whatever state it was previously in unless you are below the TCC release speed in the gear you just shifted into. So if you want to go from 3rd locked to 4th unlocked, you will need the TCC release speed table to be above the 3-4 upshift table which is, generally speaking, not practical because you'll be running unlocked far to often to be efficient. I think most people just move 3rd gear lockup out of the way, but I don't like that option much either because, when towing, it's worth about 1-2 mpg if you are pulling a hill in 3rd locked vs unlocked and generates a lot less heat when locked. I just let it shift when locked with very aggressive torque reduction.
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