scottdownsouth
scottdownsouth Reader
5/8/19 4:48 p.m.

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 !

 

Vigo
Vigo UltimaDork
5/8/19 10:50 p.m.

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. 

Ranger50
Ranger50 UltimaDork
5/9/19 6:45 a.m.

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.

Curtis
Curtis UltimaDork
5/9/19 9:19 a.m.

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?

rslifkin
rslifkin UltraDork
5/9/19 9:29 a.m.

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.  

scottdownsouth
scottdownsouth Reader
5/9/19 6:13 p.m.

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. 

californiamilleghia
californiamilleghia HalfDork
5/9/19 7:03 p.m.

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

scottdownsouth
scottdownsouth Reader
5/9/19 7:37 p.m.

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

Patientzero
Patientzero New Reader
5/10/19 2:11 p.m.

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.

 

rslifkin
rslifkin UltraDork
5/10/19 2:15 p.m.
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.  

Patientzero
Patientzero New Reader
5/10/19 2:23 p.m.

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.

scottdownsouth
scottdownsouth Reader
5/10/19 4:06 p.m.

In reply to Patientzero :

I have the biggest cooler that will fit

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