Towing in NWGA

Hey Folks,
Been lurking a few months to gather info.
I've got a Dedicated Rig towing a 4500-5000lb trailer with a 1995 K1500 Suburban 5.7l 4l60e 3.42, using a 16197427.
Only mods are ultimate tbi shaping and transgo sk kit with upgraded 3-4 pack during rebuild.
I've got a g1 clone from red devil river, a generic chip burner, and a few chips coming.
The hope is to start with adding tow/haul to cruise tables, or modify current tables to those.
Once I get the hang of copypasting codes, I will be looking at a mtc-1 cam to help tackle hills.
My location affords a heavy HWY mileage split between City, so I'm trying to take advantage of that, and use shift tables to help the 4l60e last in it's role.
Any info regarding trans table tuning, especially tow haul, would be appreciated.

The attached Bluecat Transmission Table Software is a good option.

https://forum.hptuners.com/showthrea...Table-Software . . . post #210 https://www.camaro5.com/forums/showp...08&postcount=2

So far, I used a bin file from the library that matched my ecu and code : BJYK 95 C-K Truck 5.7TBI 4l60e with 3.08 or 3.42 gears , And used bin : 2002 Chevrolet Express Van Automatic L31 5.7L 4L60e 2wd (12212156) Lean Cruise , with Universal Patcher to get at the performance tables and pressures, assuming they're tow/haul tables.

I then copy/pasted table by table for all filters marked performance in the van bin.

*** I averaged two adjacent cells in the van's base pressure performance tables to collapse the 33 data points to fit on the 17 line tables of the c-k bin at tables : Pressure Offset vs. TPS vs. Gear , And Load Based Pressure Offset vs. TPS vs. Gear***<<< Is this correct??

I left the upshift rpm table as stock, figuring there are torque curve differences between L05 and L31 engines.

I also bumped max line pressure to 92 from 90, for no reason whatsoever.

After a test drive with the trailer unhooked, I can say that the pattern has shifted towards holding whatever gear it's in longer. Shifts are extremely positive, I'm wondering if I over did the base pressure tables with having the shift kit on there already. Zero to Part Throttle at low speed feels like an on/off switch, can feel the gear reengaging everytime, I thought tow/haul would hold the gear on decel also? Going to hook a pressure gauge on it and maybe tote the trailer a bit in a few days.

If anybody wants to look at this, I added the files used. Thanks for any input. edit files removed

Quote:

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Originally Posted by jc222r

So far, I used a bin file from the library that matched my ecu and code : BJYK 95 C-K Truck 5.7TBI 4l60e with 3.08 or 3.42 gears , And used bin : 2002 Chevrolet Express Van Automatic L31 5.7L 4L60e 2wd (12212156) Lean Cruise , with Universal Patcher to get at the performance tables and pressures, assuming they're tow/haul tables.

I then copy/pasted table by table for all filters marked performance in the van bin.

*** I averaged two adjacent cells in the van's base pressure performance tables to collapse the 33 data points to fit on the 17 line tables of the c-k bin at tables : Pressure Offset vs. TPS vs. Gear , And Load Based Pressure Offset vs. TPS vs. Gear***<<< Is this correct??

I left the upshift rpm table as stock, figuring there are torque curve differences between L05 and L31 engines.

I also bumped max line pressure to 92 from 90, for no reason whatsoever.

After a test drive with the trailer unhooked, I can say that the pattern has shifted towards holding whatever gear it's in longer. Shifts are extremely positive, I'm wondering if I over did the base pressure tables with having the shift kit on there already. Zero to Part Throttle at low speed feels like an on/off switch, can feel the gear reengaging everytime, I thought tow/haul would hold the gear on decel also? Going to hook a pressure gauge on it and maybe tote the trailer a bit in a few days.

If anybody wants to look at this, I added the files used. Thanks for any input.

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Lower the Max back to 90. 92 actually decreases max line pressure. Its a value for the EPC not an actual pressure.

The newer OBD2 PCMs control line pressure off estimated torque output. You are not going to have good results trying to rescale them into TPS values. I would suggest max line pressure somewhere around 50% throttle with a strong rise immediately off idle, then smoothly ramp up to max as the throttle increases. The sharp initial rise is important because it does not take much throttle opening at low rpm to build torque.

Tow/Haul only changes the upshifts, its not grade braking. Need to have the shifter in 3rd so that the over run clutch is engaged. NEVER TOW in 4th. My Express van smoked the stock 60E in 38K miles and a really built 65E in 40K with no towing. No need to tear up the weak 60E trying to tow in 4th they have a hard enough time moving a 6,000 lbs vehicle down the road without converting themself to all neutrals.

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Originally Posted by Fast355

Tow/Haul only changes the upshifts, it's not grade braking. Need to have the shifter in 3rd so that the over run clutch is engaged.
NEVER TOW in 4th.
My Express van smoked the stock 60E in 38K miles, and a really built 65E in 40K with no towing.
No need to tear up the weak 60E trying to tow in 4th they have a hard enough time moving a 6,000 lbs vehicle down the road without converting themself to all neutrals.

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Even if the shift tables are written to downshift to 3rd or 2nd assertively, yes, absolutely, the shifter needs to be kept OUT of OverDrive to make any use of the overrun clutches.
Don't forget to upgrade the ATF cooler.
For towing / hauling in 4th gear, the MINIMUM rear axle gear should be 4.10.

Yes, I always tow in 3rd gear. That explains the difference I felt during the test drive in od unhooked, no overrun. After reading a forum post on hptuners website, it was said that shift timing tables should be zeroed out when a shift kit is installed, otherwise the pcm will pull pressure to meet the shift time if it's populated. Is this correct? When I populated the shift timing tables, I noticed that the stock c-k bin was basically zeroed out except for 2nd upshift which had values entered. I attached a screenshot of stock tune vs modified. I definitely dont want to pull pressure for quicker shifts, so is it reasonable to re-zero the shift time tables? ***I also noticed the upshift MPH vs time , and downshift MPH vs time are inverted with respect to the stock tune. I have not collapsed the pressure tables to ramp faster just yet. Max line pressure put back to stock 90.

Thanks for the quick replies and info!

EDIT: DONT USE THESE NUMBERS

Using the modified table on the 'load based pressure offset' and zeroing out the 'pressure offset' like the stock table, pressure gauge reads about 90-120 in first light throttle, 120-240! in 2nd at light throttle, and 150-180 in third cruise light throttle. I think I should zero out the load based pressure offset or atleast return to stock negative numbers, damn sure dont want to destroy the pump, gauge was buzzing... 2nd and 3rd have very little throttle input before going above 200.

Quote:

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Originally Posted by jc222r

Yes, I always tow in 3rd gear. That explains the difference I felt during the test drive in od unhooked, no overrun. After reading a forum post on hptuners website, it was said that shift timing tables should be zeroed out when a shift kit is installed, otherwise the pcm will pull pressure to meet the shift time if it's populated. Is this correct? When I populated the shift timing tables, I noticed that the stock c-k bin was basically zeroed out except for 2nd upshift which had values entered. I attached a screenshot of stock tune vs modified. I definitely dont want to pull pressure for quicker shifts, so is it reasonable to re-zero the shift time tables? ***I also noticed the upshift MPH vs time , and downshift MPH vs time are inverted with respect to the stock tune. I have not collapsed the pressure tables to ramp faster just yet. Max line pressure put back to stock 90.


Thanks for the quick replies and info!

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Target a reasonable shift time. 250-300 msec is about the shortest I will go. The PCM will ramp the pressures up trying to get a shift that matches the shift time. Anybody that suggest zeroing them honestly does not know what they are doing.

300 msec is extremely firm and 250 msec is boarderline harsh.

This was 250 msec. Stock 60E with a S10 converter and Billet 2nd and 4th servos. No shift kit. L31 with a LT1 cam and long tubes.

https://youtu.be/LYdyu501Z4Y

PS I have never seen on Zerod out stock.

I've got the shift times set in the 5-600 msec range, lowest is 475, all from the chevy van performance mode setting. After hooking the gauge up and seeing pressure spike to max at light throttle, I realized the table I've been messing with is additive to the 0-64 and 64-128 pressure tables.
I went back and capped pressures at 30 psi. This kept the max pressure of 2 and 3 at around 180-200, with a light throttle hovering in 120-150 range, so much better. Is the 0 pressure at 0 tps necessary for something, or can I add a low positive value? So far, line pressures are much more progressive compared to stock.

Quote:

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Originally Posted by jc222r

I've got the shift times set in the 5-600 msec range, lowest is 475, all from the chevy van performance mode setting. After hooking the gauge up and seeing pressure spike to max at light throttle, I realized the table I've been messing with is additive to the 0-64 and 64-128 pressure tables.
I went back and capped pressures at 30 psi. This kept the max pressure of 2 and 3 at around 180-200, with a light throttle hovering in 120-150 range, so much better. Is the 0 pressure at 0 tps necessary for something, or can I add a low positive value? So far, line pressures are much more progressive compared to stock.

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I don't see a need to have line pressure increase at 0% TPS or 0 MPH. If you do anything maybe add some from 30% TPS and above at 0 mph. That way you make sure there is enough line pressure for starting a load off uphill.

IIRC correctly my 700r4 with shift kit, elevated line pressure spring, and oversized boost valve made 230 psi in TV Boost mode.

Also FYI, maximum line pressure is set mechanically. The EPC just reduces line pressure for idle and part-throttle. You want maximum line pressure under load.

Quote:

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Originally Posted by Fast355

Also FYI, maximum line pressure is set mechanically. The EPC just reduces line pressure for idle and part-throttle. You want maximum line pressure under load.

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I thought the max from factory was about 200, So I'm shooting for that. Last run with it hitting 240 I was feeling a defined buzz in pressure line, and audible whining if pump, very unsettling. I've got a .500 boost valve with trangso sk kit on it. Reverse can slap 300 on a stall test. I figured factory max of 190+10 should get a good clamp without blowing circuit somewhere. Thanks for the quick replies, great suggestion on the uphill starts, I do a bunch of those.

Quote:

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Originally Posted by jc222r

I thought the max from factory was about 200, So I'm shooting for that. Last run with it hitting 240 I was feeling a defined buzz in pressure line, and audible whining if pump, very unsettling. I've got a .500 boost valve with trangso sk kit on it. Reverse can slap 300 on a stall test. I figured factory max of 190+10 should get a good clamp without blowing circuit somewhere. Thanks for the quick replies, great suggestion on the uphill starts, I do a bunch of those.

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Factory build should be around 200 max. Shift kit and boost valve will change that. Reverse is always higher. Pressure I quoted on 230 was full TV extension at 2,000 rpm. 230-240 is not unusual with a shift kit. Continuous high line pressure is hard on the pump and really heats the fluid. I would say anything 235 psi and under for short periods of high load probably will not hurt it. I always tried to stay under 275 in reverse. From memory I want to say 250ish is stock reverse pressure. Part of the shift kit is getting more fluid volume and less accumulator dampening which allows a more positive shift without as much line pressure. You may find acceptable results at 200 psi especially less than WOT. You can always set it lower and then put some added pressure in the PE adder table for when the engine is really working hard.

It has been a long time since I have datalogged P4 transmission data. There is a surpising amount of data from the data stream on the transmission side that will help dial the transmission settings in. Shift time commanded, shift time error, epc values, transmission slip data, etc.

Rain/fog held up any more fiddling. I did verify what ben73 found in http://www.gearhead-efi.com/Fuel-Inj...ressure+offset about the load based table adding to the overall pressure tables. I swapped in a stock tune and pressures rarely went above 120 at part throttle, mostly 90-110 and close to 180 under heavy almost WOT, cruise in 3rd is about 110-120.
With the modified tune, part throttle is much more responsive to throttle, from 120 to 210 at wot. 3rd cruises at min 150 light throttle and goes up from there. So without messing with the overall pressure tables, using the load based pressure offset table adds in a set amount of psi per gear in case anybody is following along. The stock tune has negative numbers in this table. That's for 2,3,4 I havent found a table to increase 1st by itself.

are you reading those pressures with a mechanical gauge or just looking at the datalog? commanded pressure and ACTUAL pressure are 2 different things...

There is NO sensor to measure pressure In the transmission, therefore no pressure reading in the datalog. This is how tuners get themselves into trouble and ruin transmissions.

Mechanical readings. I get what you mean, first run was full line pressure at anything above light throttle. I've scaled the pressure added way back, it's got to be a percentage based number instead of psi that the table is labeled in. Max is 20 added, will probably go lower.

I ended up with a max of 12 in the load based pressure table. That put most shifts at part throttle around 120-150, cruise in 3rd at min 150, and all wot shifts at 190-210. That's with a 500 boost valve and transgo sk kit. The psi field heading is wrong; putting 10 in the pressure table returns a rise of about 24-30 psi, which equates to 10 percent of max line pressure 240-300 (I can't stare at gauge while driving). The first run I had everything at 90 assuming 90psi, but it was max line pressure, good thing I never went wide open during first drive. In the 0-64 mph pressure table, I added roughly 10-20 percent in columns below 16 mph, to increase pressure in 1st for uphill starts while towing. Overall, shift feel is closer to stock tune, with longer 1-2 2-3, and pressures holding middle 100's instead of low 100's. Hope this helps somebody.

All the "psi" values are really just the lookup column in the EPC or force motor tables, the current tables for the pressure control solenoid. It's a table of temperature vs pressure giving currents. I don't see it in your list, but it'll be there. Being labelled psi is the biggest mistake in the tuning info you will find. That's why you never go outside the 0-96 range because the table being looked up only has 0-96 columns.