2003 Suburban 2500 6.0/4l80e Basic Tuning Questions

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01-29-2023
Kannif82

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2003 Suburban 2500 6.0/4l80e Basic Tuning Questions

First post here and have been doing quite a bit of reading alongside some videos from Goat Rope Garage and a few others. Doing some basic tuning items on my Suburban 2500 with the 6.0/4L80e setup to eliminate the PE cycle timing and remove some of the TQ Management. Tossed the changes below once I had the speedo corrected. Not looking to set the world on fire with the Suburban, but wanting to clean up some of the slow response and fat in the stock power tune.
Engine > General > TQ vs RPM - 10,000/per field
Engine > General > Spark Retard vs Torque Reduction - removed 50%
Engine > Fuel > PE > Delay - 0 Seconds
Engine > Fuel > PE > Enrichment Rate - 1.000
Trans > Shift Pressures > Upshift > General - Performance field applied to Perf & Normal

Problem - Cruising 60mph and give it 100% tps the truck seems to unlock 4th and pull up to 3K or so and increase speed, but not drop to 3rd gear like you'd think. Passing power is very limited and assuming I am missing a setting to not allow it to kick down to say 3rd when cruising 60mph or on the highway trying to pass etc... I have attached the file I'm currently running for review and thanks in advance for any help, direction or pointers that come from this. Again not wanting to dial this truck to the gills, but wanting to clean up some fat and at stock power levels, have all of it on tap when needed.

Ken
01-29-2023
Fast4.7

Quote:

Originally Posted by Kannif82

First post here and have been doing quite a bit of reading alongside some videos from Goat Rope Garage and a few others. Doing some basic tuning items on my Suburban 2500 with the 6.0/4L80e setup to eliminate the PE cycle timing and remove some of the TQ Management. Tossed the changes below once I had the speedo corrected. Not looking to set the world on fire with the Suburban, but wanting to clean up some of the slow response and fat in the stock power tune.
Engine > General > TQ vs RPM - 10,000/per field
Engine > General > Spark Retard vs Torque Reduction - removed 50%
Engine > Fuel > PE > Delay - 0 Seconds
Engine > Fuel > PE > Enrichment Rate - 1.000
Trans > Shift Pressures > Upshift > General - Performance field applied to Perf & Normal

Problem - Cruising 60mph and give it 100% tps the truck seems to unlock 4th and pull up to 3K or so and increase speed, but not drop to 3rd gear like you'd think. Passing power is very limited and assuming I am missing a setting to not allow it to kick down to say 3rd when cruising 60mph or on the highway trying to pass etc... I have attached the file I'm currently running for review and thanks in advance for any help, direction or pointers that come from this. Again not wanting to dial this truck to the gills, but wanting to clean up some fat and at stock power levels, have all of it on tap when needed.

Ken

Get a copy of Blucats and adjust the transmission tables.
01-29-2023
Kannif82

I?ve seen some references to that, any pointers or pretty self explanatory? Will download this evening and tinker with.
01-29-2023
RDF1

What size tires do you have?
01-29-2023
kingtal0n

Never run the trans at WOT in D4 selector.
You don't really want the transmission to automatically downshift from 4th to 3rd while the gear lever is in D4 approaching WOT. While in D4 the 4l80e over-run clutches are off so you could damage the roller clutch if this happens. Its better to let it stay in 4th while in D4. If you want 3rd, downshift manually to 3rd D3 to bring on the over-run clutches.

Sonnax makes a 'fix' for this
https://www.sonnax.com/parts/4496-sm...utch-valve-kit

I don't like keeping the clutches on all the time as it consumes additional energy and economy. So damned if you do and damned if you don't.
01-29-2023
Kannif82

Quote:

Originally Posted by RDF1

What size tires do you have?

285/75r16
01-29-2023
Kannif82

1 Attachment(s)

Anything I look to be missing?

Attachment 127927
01-30-2023
Fast4.7

Quote:

Originally Posted by kingtal0n

Never run the trans at WOT in D4 selector.
You don't really want the transmission to automatically downshift from 4th to 3rd while the gear lever is in D4 approaching WOT. While in D4 the 4l80e over-run clutches are off so you could damage the roller clutch if this happens. Its better to let it stay in 4th while in D4. If you want 3rd, downshift manually to 3rd D3 to bring on the over-run clutches.

Sonnax makes a 'fix' for this
https://www.sonnax.com/parts/4496-sm...utch-valve-kit

I don't like keeping the clutches on all the time as it consumes additional energy and economy. So damned if you do and damned if you don't.

Not a problem that I have run across, then again once you start making decent power it is not very common to go WOT from speed. When I am around town I am in 3rd gear because I need the engine braking anyway.

As far as keeping the clutches on all the time and losing fuel mileage, it really does not matter if you know how to modulate your speed. Might hurt the fuel mileage of some pedal pumper that cannot modulate the pedal to save their life. My personal experience is that fuel mileage is better if you are in DFCO whenever you are off the throttle and brakes last alot longer.
01-30-2023
kingtal0n

Quote:

Originally Posted by Fast4.7

Not a problem that I have run across, then again once you start making decent power it is not very common to go WOT from speed. When I am around town I am in 3rd gear because I need the engine braking anyway.

As far as keeping the clutches on all the time and losing fuel mileage, it really does not matter if you know how to modulate your speed. Might hurt the fuel mileage of some pedal pumper that cannot modulate the pedal to save their life. My personal experience is that fuel mileage is better if you are in DFCO whenever you are off the throttle and brakes last alot longer.

I just mean, we look at the factory over-run clutch enable tables, its clear they didn't want the clutches on in D4 for some reason. Even though it weakens the transmission. All of the input shaft demand is placed on the roller clutch in D4 for gears 1 2 3. I just assumed the reason the factory did this was to save fuel, reduce friction, reduce pump demand. I can't see any other reason unless I'm not thinking of something else.

It's just common knowledge this is a weak point of the 4l80e

Quote:

Any 4L80e needs to be put into D3 when giving it the business.

https://www.performancetrucks.net/fo...3/#post5408264

Quote:

Originally Posted by Fast355

Have had zero problems with that in either of my 4L80/85 setups. Get a better tuner! Converter unlocks, trans downshifts and it goes. If 8.1Ls don't tear them up towing a small block won't either.

Its not a tuning issue its a transmission internal flaw.

The roller clutch isn't backed up by the over-run clutches

Quote:

The production roller clutch will eventially fail. Overrun clutch plate only apply when you manually downshift to D3, D2, D1.

https://ls1tech.com/forums/automatic...h-w-4l80e.html

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Better to educate the operator that trans needs to be in 3rd gear when hot rodding.

https://ls1tech.com/forums/automatic...l#post20382788

Quote:

The OD roller is the weakest link in a 4L80E. The only range it is not loaded is P/N and 4th gear. Time bomb under load or horsepower

https://www.yellowbullet.com/threads.../post-73541393

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I use it when I think a customer might forgot to pull shifter into d3.

https://www.yellowbullet.com/threads.../post-73542135

Quote:

I also like it for trucks that I know will haul heavy and make multiple 4-3-4-3-4-3 type shuttle shifts.
For high HP units, if the driver knows to use D3 and drive the thing right.

Quote:

ust a little FYI when doing any WOT runs with a 4L80e, never have the shifter in D4 (drive)

https://forum.hptuners.com/showthrea...l=1#post437126

Quote:

But NEVER beat on it or launch in D4!!!

https://bobistheoilguy.com/forums/th...2/post-5395938
01-31-2023
Fast4.7

Quote:

Originally Posted by kingtal0n

I just mean, we look at the factory over-run clutch enable tables, its clear they didn't want the clutches on in D4 for some reason. Even though it weakens the transmission. All of the input shaft demand is placed on the roller clutch in D4 for gears 1 2 3. I just assumed the reason the factory did this was to save fuel, reduce friction, reduce pump demand. I can't see any other reason unless I'm not thinking of something else.

It's just common knowledge this is a weak point of the 4l80e

https://www.performancetrucks.net/fo...3/#post5408264

Its not a tuning issue its a transmission internal flaw.

The roller clutch isn't backed up by the over-run clutches

https://ls1tech.com/forums/automatic...h-w-4l80e.html

https://ls1tech.com/forums/automatic...l#post20382788

https://www.yellowbullet.com/threads.../post-73541393

https://www.yellowbullet.com/threads.../post-73542135

https://forum.hptuners.com/showthrea...l=1#post437126

https://bobistheoilguy.com/forums/th...2/post-5395938

Well while what you are saying might help if you are making huge power. I will add I still beat the snot out of the 4L80E behind an 8.1L making 550 tq in Drive. At this point if the roller clutch goes, it goes, the unit is probably due a rebuild anyway. I put the shifter in Drive in my Tahoe and go. As I have pointed out before plenty of these live long lives in Drive behind big block motor homes, 8.1L medium duty trucks and heavy cutaway chassis Express vans with Duramaxs. The roller clutch is stronger than you think it is. GM rates the trans to 440 tq with an 80E and 460 tq with an 85E with no special driving style modifications. Put it in drive at max GVWR, floor it and go. The way GM tuned them, nothing will get hurt. If an 8.1L or Duramax is not hurting a 4L80E a 6.0L certainly will not.

Remember GM also does some of what they do for smoothness. A person with a jerky on/off pedal foot would have a the vehicle jerking like an inexperienced manual trans driver without the over run clutch active.