Upgrading my 1999 Suburban C1500 for better towing performance

[Fast355]

Definately not impossible to swap to the full 1-ton running gear. I did it on my Express van. I actually drove it for a few days with the 3500 rear end and 1500 front end under it. Suprisingly it did not even throw and ABS code.

My 10.5 has 5.13s and I am running a LT265/75R16. With the 85E I tow in OD. My 350 is far from stock. 215cc ported aluminum heads, 215/224 comp cam, 1.7 rockers, thorley tri-ys, full exhaust, coil per cylinder 24x ignition, ported marine intake with 3.8 injectors that flow 42 lb/hr. Also have hydroboost, all the fluid coolers, helwig 1 3/8" rear anti sway bar. 1 ton springs, 1 ton brakes and air bags in place of the rear bump stops.

I tow a large Jayco travel trailer with mine.

[dave w]

Maybe EFI Live ( https://www.efilive.com/latest/cat/download-efilive ) would be an option for tuning either the 99 PCM or 2002 PCM?

Attached are EFL Live files from a 1998 Pickup (the 1999 is very similar) I'm currently working on. The EFI Live files will work with the "Free Version" of EFI Live that can be downloaded in the link above.

For transmission tuning check out Bluecat: https://forum.hptuners.com/showthrea...Table-Software

EFI Live and Bluecat have steep learning curves!

dave w

[Machine_whisperer]

UPDATE:
My mods have come along nicely. I swapped out the rear end to 3.73, along with all new brake parts. I did the NBS master cylinder swap. I bought the tow/haul button out of a 2003 Chevy Express van. I did the 411 swap with a junkyard 411 from a 2001 Express 1500. My truck started right up after a security relearn and ran better than ever with no tuning. I found that grounding C1-71 did nothing at all. I downloaded PCM Hammer and TunerPro RT and bought a $30 OBDLink interface. Then I did a PCM read with PCM Hammer, found a definitions file on the internet, and used TunerPro RT to open that and the .bin read from my truck. I switched the performance shift trigger to use pin C1-71, made my max speed match my speedometer, and turned off vats. Then I saved the .bin and wrote it to the truck.

I didn’t really notice any difference with tow/haul activated. I will post a new question about proper settings for tow haul, because now it is down to that. I’ve towed heavy trailers with a 2013 Silverado 2500, and the tow/haul was an amazing difference. In the meantime, I am going to open up a bin for a GMT800 Suburban 2500 and compare those tables.

[THEFERMANATOR]

Pretty sure the vans tow/haul switch is a serial type switch, and for the method you're using all you need is a momentary switch to ground. As to the actual tow/haul tables, they're not that different from the regular tables. You have to remap them to be an actual tow/haul table.

[Machine_whisperer]

I found the button on Tuner Pro that graphs the table values. The stock performance tables are noticeably different in 3D. I’m going to call it good enough until I get my 32’ camper that weighs 5400# empty. Maybe an Airlift system before then. I am still open to hearing specific adjustments that can be made to improve things.

[Fast355]

I found the button on Tuner Pro that graphs the table values. The stock performance tables are noticeably different in 3D. I’m going to call it good enough until I get my 32’ camper that weighs 5400# empty. Maybe an Airlift system before then. I am still open to hearing specific adjustments that can be made to improve things.

Get a copy of blue cats and remap the shift points.

For tow haul I set the preference to lock the torque converter in acceleration from 2-4th gear. Do that by setting acceleration lock to 2nd gear in blue cats. With a 4L60E I leave the WOT lockup option off which you do by setting WOT lockup to gear 5. Set the minimum RPM to 1,800 rpm as that will keep the RPM up when accelerating and keep the shift points from allowing the engine to drop too low in rpm. Then again look at the factory Tow/Haul settings for an 02 Astro Van and they will get you close. The overall gearing and powerband of the engine are very similar. For Tow/Haul I would set all the command shift times to 0.300 for 1-2 and 2-3 and set to 0.00 for 3-4. Anything over about 260 ft/lbs of torque should have a 40% torque reduction for 1-2 and 2-3 upshifts.

[Machine_whisperer]

Get a copy of blue cats and remap the shift points.

For tow haul I set the preference to lock the torque converter in acceleration from 2-4th gear. Do that by setting acceleration lock to 2nd gear in blue cats. With a 4L60E I leave the WOT lockup option off which you do by setting WOT lockup to gear 5. Set the minimum RPM to 1,800 rpm as that will keep the RPM up when accelerating and keep the shift points from allowing the engine to drop too low in rpm. Then again look at the factory Tow/Haul settings for an 02 Astro Van and they will get you close. The overall gearing and powerband of the engine are very similar. For Tow/Haul I would set all the command shift times to 0.300 for 1-2 and 2-3 and set to 0.00 for 3-4. Anything over about 260 ft/lbs of torque should have a 40% torque reduction for 1-2 and 2-3 upshifts.

I googled Blue Cats and came up with nothing. Maybe TunerPro will let me do this? Thanks for the info, I’ll take a look at the Astro maps and compare to what I have