Max Tow Package Components

Jon A · March 13, 2016

1) 8L90 might be, but the trucks they install it in aren't rated that high.

Not yet, anyway. But you're only making my point for me. The 8L90 is stronger than the 6-speed used in the gas HD's so it's more than strong enough for any load with a light duty. I pointed that out because you were talking about the Allison for some reason.

2) 8L90 is not available with 3.73's

I think you misunderstood. He already has the truck. It has 3.23's. What is available on new trucks is meaningless. He was considering a gear change. I pointed out 3.73's would be exactly the same cost as 3.42's if swapping and would provide a much more worthwhile change. I don't think I'd bother with the hassle to only go from 3.23's to 3.42's.

Jon A · March 13, 2016

I will probably only tow 6 times a year. And long distance maybe once or twice a year.The long distance will likely be between Illinois and Florida so little high altitude pulling.

That info helps a bunch. I think you can probably scratch 2 of the 3 off your list of needs if you're not crossing any major mountain ranges.

I like the idea of the Air Lift verses adding the heavy duty springs.Seems like the best of both worlds. The Load Lifter 5000 seems pretty easy to install. https://www.airliftcompany.com/shop/57204/

Yes, those are excellent. I have the "Ultimate" version with the internal bumpstops--which you probably don't need unless you drive like a maniac offroad as I do. The bags provide a dramatic improvement in ride and handling when towing.

It's hard for people to understand, who haven't studied vehicle dynamics and suspension design, exactly why they're so beneficial. The floaty, bouncy feeling of the front end, (even full porpoising), is primarily cause by lack of spring rate in the rear. This is why it's rarely a problem with 2500's and 3500's even when not using a WDH (of course you still want to use one with your truck/trailer). The airbags can add a great deal of spring rate eliminating that tendency. And by eliminating sag, you won't be slamming into the bumpstops as you drive down the road so you get a much better ride along with the better handling. And when you're not loaded, lower them to 5-10 psi and you won't even know they're there.

What I am trying to say is that it seems the 3.23 might be just fine for what I want to do.

I agree. Gears are a lot less needed with the 8-speed than they are with the 6-speed. If you had a 6-speed and were going to be towing over the rockies, etc, I'd strongly recommend doing them but the 8 speed on generally much flatter ground really isn't going to need them, especially with the 6.2.

I also wouldn't bother changing the radiator. The stock system should do just fine if you're not pulling up any long, steep mountain passes. If you want a cheap/easy cooling improvement a 180 thermostat will help at highway speeds even without tuning. It'll help even more with the fans tuned to turn on earlier but it'll be beneficial even without if want to avoid tuning for warranty purposes.

I do think you're towing enough that some E or at least D rated tires are a very good idea for better handling and increased safety. Better shocks are a nice addition as well and can improve the ride and handling year-round, not just when you're towing.

xray58 · March 14, 2016

The Ultimate version of the Air Lift might be the way I go also.

I do have RPO codes for the KC4 (Cooling, external engine oil cooler) and KNP (Cooling, auxiliary external transmission oil cooler) options.

After reading your last comment I looked at the tires that came on my truck. They now look like the weak point to me. I will be saving up for some 8 or 10 ply tires.

Once I wear this truck out by putting 60-70K miles on it I may have to upgrade to a Duramax 2500 or 3500 and get a real truck. Someday I would like to go with a nice 5th wheel and I am guessing that will be required. Although I sure like the sound of this V8 when you get on it. It is pretty impressive and the acceleration reminds me of a 1970 Monte Carlo I bought when I returned from the service. It had a 3 speed auto with a 400 big block but the funny thing is that I think this truck may be as fast as the car was. At least to 100 MPH anyway.

1300c · March 15, 2016

That info helps a bunch. I think you can probably scratch 2 of the 3 off your list of needs if you're not crossing any major mountain ranges.

Yes, those are excellent. I have the "Ultimate" version with the internal bumpstops--which you probably don't need unless you drive like a maniac offroad as I do. The bags provide a dramatic improvement in ride and handling when towing.

It's hard for people to understand, who haven't studied vehicle dynamics and suspension design, exactly why they're so beneficial. The floaty, bouncy feeling of the front end, (even full porpoising), is primarily cause by lack of spring rate in the rear. This is why it's rarely a problem with 2500's and 3500's even when not using a WDH (of course you still want to use one with your truck/trailer). The airbags can add a great deal of spring rate eliminating that tendency. And by eliminating sag, you won't be slamming into the bumpstops as you drive down the road so you get a much better ride along with the better handling. And when you're not loaded, lower them to 5-10 psi and you won't even know they're there.

I agree. Gears are a lot less needed with the 8-speed than they are with the 6-speed. If you had a 6-speed and were going to be towing over the rockies, etc, I'd strongly recommend doing them but the 8 speed on generally much flatter ground really isn't going to need them, especially with the 6.2.

I also wouldn't bother changing the radiator. The stock system should do just fine if you're not pulling up any long, steep mountain passes. If you want a cheap/easy cooling improvement a 180 thermostat will help at highway speeds even without tuning. It'll help even more with the fans tuned to turn on earlier but it'll be beneficial even without if want to avoid tuning for warranty purposes.

I do think you're towing enough that some E or at least D rated tires are a very good idea for better handling and increased safety. Better shocks are a nice addition as well and can improve the ride and handling year-round, not just when you're towing.

Good post! I agree with everything you said except one small point, and this is just coming from what I've experienced. The 6.2l without the max tow that I towed a 9000lb trailer with had the temperature gauge rise a mark to a mark, and a half on every uphill we went (not large ones either), and it was only 65 degrees. I got a chance to tow the same trailer on the same route with the max tow on an 85 degree day, and the temp gauge never moved. That being said the 180 thermostat may very well fix that problem, and I would try that before I replaced the radiator. Maybe have the bcm reprogrammed to allow the fans to kick on full speed at a lower temp to maybe? But I've never messed with a programmer so I have no idea if that could be done. The different cooling did make a big difference.

Jon A · March 15, 2016

That being said the 180 thermostat may very well fix that problem, and I would try that before I replaced the radiator. Maybe have the bcm reprogrammed to allow the fans to kick on full speed at a lower temp to maybe?

Yup, I'll bet you a million dollars it would have. I've done a lot harder than that and still kept temps very low. The stock thermostat isn't fully open until ~230 degrees and the stock fan settings don't crank them to full blast until 244 degrees.

Don't get me wrong, there's nothing wrong with a bigger radiator. That's never a bad thing to add. I'll probably do it someday just so I can check it off the list and have a bit more peace of mind. But since it appears I really don't need it, it's not at the top of my list.

It's $550 and the install is going to be more difficult than many owners are going to want to do themselves. OTOH, a thermostat is $30 and about a 10 minute install. For those already tuned for gears/tire size, etc, reprogramming the fans is free. It doesn't get much better than that!

The big hiccup is for those who don't want a tune. The thermostat will still help by itself but not as much as the combo of it and better fan settings. I'd say the NHT radiator is probably more needed for those worried about their warranty who are going to leave the fans stock.

Red_5 · March 17, 2016

Good post! I agree with everything you said except one small point, and this is just coming from what I've experienced. The 6.2l without the max tow that I towed a 9000lb trailer with had the temperature gauge rise a mark to a mark, and a half on every uphill we went (not large ones either), and it was only 65 degrees. I got a chance to tow the same trailer on the same route with the max tow on an 85 degree day, and the temp gauge never moved. That being said the 180 thermostat may very well fix that problem, and I would try that before I replaced the radiator. Maybe have the bcm reprogrammed to allow the fans to kick on full speed at a lower temp to maybe? But I've never messed with a programmer so I have no idea if that could be done. The different cooling did make a big difference.

Good to hear the upgraded radiator makes a difference, it was a big part of why I bought a Max Tow truck.

Srode1 · March 27, 2016

For example. I'm going to guess your truck has a payload of somewhere around 1500#, give or take a 100# or so. You can confirm this number by checking the yellow sticker inside your drivers door.

To me what a person is losing without the package that isn't easily corrected is the extra cooling capacity, gearing, and larger axle. The gearing will show up going up grades, it will shift more often or go to a lower gear, but that's something a person can live with I think, just not optimal. Cooling will make a difference towing heavy in hot climates like AZ and TX along with other Southern states in the Summer. You can slow down and make it less of an issue of course. The worst case would be big hills in Southern states mid Summer. For the smaller axle, just go easy getting it rolling would be my suggestion, that's when you can put the rear end under the highest load.

The easier things to adjust include shocks with increased damping, helper springs/airbag, and tires maybe depending on what you have today. Mine are rated for 2403 max load. Of course the ride will suffer a bit with these changes. I can't complain about the ride on mine, although I just came from a 2500HD Duramax Crew short bed so I don't have the best perspective on ride.

FL335i · March 30, 2016

Can anyone explain if the NHT Max trailer package on the LT 1500's with 5.3's include external trans coolers or not? B/c from what I researched, it does not. The radiator is "larger" which has the trans lines hooked to it hence making the trans cooler portion larger.

Shocks. Seems like everyone hates the AC's. What is the recommendation? Monroe's? I bought my '14 and picked the 3.42 gearing, G80 locker etc. However at the time the NHT max trailer pkg was not readily available on lots. I'm integrating a Tekonsha P3 BC into the dash where I have a pocket as some other members on here have done. So no hard feelings not having the OE IBC. I want to have the radiator/trans cooler, mirrors and rear springs and good shocks.

Side note. I've already installed a spin-on coolant filter kit. And next is a remote spin-on filter for the trans to run a Napa Gold 1269 10 micron filter. But I'd like to address the radiator and/or trans cooler at the same time.

xray58 · April 1, 2016

Well I ended up buying a 38ft travel trailer. The dry weight is 7800 lbs. I think this is probably about right for my setup where my max towing is 9300 lbs.I still may upgrade my tires to the e load rating though. I have heard it may make it more stable and less susceptible to sway. I did buy the Blue OX sway pro and seems pretty stable now after driving almost 1000 miles. The first 200 miles or so was in real windy conditions which was pretty nerve racking since I have never pulled a travel trailer this long.

Going up and down some of the hills in southern Kentucky and Northern Tennessee were a breeze with the 6.2L. Just set the cruise and let it work. That engine is really amazing.I averaged about 9 MPG pulling the trailer and running 70-75 MPH.

Enthusiast, I am not sure which ones come with the larger cooling but you can check for the RPO codes in the glove box on already built units. The RPO codes are: KC4 (Cooling, external engine oil cooler) and KNP (Cooling, auxiliary external transmission oil cooler)

One thing I did find out from the retired guy I camped next to in Florida. That is this stuff is addicting. I am already looking to upgrade the truck and trailer. Crazy!

FL335i · April 2, 2016

xray58- Thanks for the heads up on the PRO codes. I'm checking my truck tomorrow. I have a PRO code list I found online tonight also. As for camping in FL, where are you "camping" with a 38ft trailer? More like parked.

xray58 · April 5, 2016

FL335i, We stayed at Santa Rosa RV Park in Navarre,FL. It was a last minute trip and reservation. The place was really nice. I had to park my truck sideways on the pad but it worked.

FL335i · April 5, 2016

Ah, the panhandle.... The emerald coast.

newdude · April 5, 2016

Not yet, anyway. But you're only making my point for me. The 8L90 is stronger than the 6-speed used in the gas HD's so it's more than strong enough for any load with a light duty. I pointed that out because you were talking about the Allison for some reason.

Is it though? If we go by the GM transmission identification process, they both have a "90" as their last digit, which identifies the "torque" capacity so to speak. Both are found behind supercharged variants in other cars (6L90 in the 2012-2015 ZL1 and 8L90 behind all current LT4 engines). 6L90 is behind the Duramax in Express/Savana vans. I'd say they are equally as strong IMO, just one has two more gears and can shift faster, especially in its performance applications.

Can anyone explain if the NHT Max trailer package on the LT 1500's with 5.3's include external trans coolers or not? B/c from what I researched, it does not. The radiator is "larger" which has the trans lines hooked to it hence making the trans cooler portion larger.

All V8 trucks have an aux. transmission cooler. NHT or not. NHT gets you a larger main radiator.

FL335i · April 5, 2016

15HDriver. You are correct. I learned that going through part #s. Glad to hear I got it correct. I am planning to swap out to the larger radiator soon. Preparing for my boat

Jon A · April 5, 2016

Is it though? If we go by the GM transmission identification process....

Yes, it is. If we go by GM's actual rating for the transmissions, the 6L90 is good for 520-531 lb-ft of engine torque. The 8L90 is good for 635 lb-ft of engine torque.

http://www.gmpowertrain.com/VehicleEngines/PowertrainProducts.aspx

The point was the 8L90 is way, way, way stronger than it needs to be for a 1/2 ton, even towing way more than it's rated to tow. There are lots of reasons to not tow that much with a 1/2 ton, but that the 8L90 might not be up to it is not one of them.