I have a question concerning adding a Super Charger to my 2013 6.0 HD. Just got it last Nov and have got an (approx.) 8,000lb travel trailer to pull. While going up fairly long inclines, the truck just doesn't seem to have enough grunt without going into lower gear and 'Screaming' at approx. 3500 - 4000 RPM! Would an Edlebrock Super Charger help/solve this problem? The truck has 77K miles but, is in very good shape. Also, where would I find the information on what type of trans that the truck has? I mean, I've heard it could be an Allison but.... How do I know? Thanks in advance.

Welcome to the forum. I believe the Allison transmission is only available with the Duramax diesel so I doubt you have that. Members here would need a little more information before making recommendations, e.g. what is your rear end ratio?, are you using the tow/haul mode? at what speed and what gear are you in when you're hitting the 3500-4000 rpm range? you may be able to find transmission and rear end production codes either in the glove box, back side of the passenger side sun visor, or the drivers side inner fender well.

Garagerog, you are correct. I don't have the Allison trans. The truck is a GMC Sierra 2500HD with the 6.0 Vortec and the 6sp Auto with 3.73 rear gear. It also has trans & oil coolers. (towing package) I bought it used last Nov with approx. 73K miles. Salesman told me he sold it originally and it was used to pull horse trailers. I've only pulled my trailer (approx. 8Klbs) the one time (in the Tow/Haul mode) speed was approx. 65-70mph and it just seemed that the truck was really struggling to make it to the top of the hill. I was checking the DIC and watching the trans temp go from 147f to 164f by the time I reached the top of the hill. Ambient temp was approx. 70f. I was in middle Ky when this was occurring with lots of steep/long hills. When starting up the hill, it didn't take long to kick down once and then again (3700-3900rpm). This is when I started watching the trans temp rise and started getting a little nervous. Other than when I was going up a hill, the truck ran/pulled fine. I'm guessing a supercharger would help with the long climbs and probably wouldn't hurt my fuel mileage too much. But, with now 77K miles, would a supercharger hurt the engine? I know this was a little long but, I'd appreciate any input as to whether I should persue the supercharger idea or just continue on in stock mode? Oh, a little more info. I plan on a trip summer/fall of 2017 out west to visit friends in South Dakota, approx. 1200 miles one way. What do you think? Thanks, Tony

Tony, first of all, your trans temps are just fine, you don't need to get nervous about them until they start climbing over 200 degrees F. I've never owned a p/u with the 6.0l but a little research tells me in your application maximum torque isn't reached until 4200 rpm which to my thinking is a bit high but that'* where you want to be when towing a heavy load up a grade. My only experience with a p/u with the tow/haul mode is my Dad'* Silverado with a 5.3, didn't take me long to ditch the switch on the stalk and just pull the shift lever into 3rd, 1:1, with your transmission that would probably be 4th gear as I assume you have 2 o/d ratios with the 6 speed. A little disclaimer here, my experience with towing a heavy load goes back years, a 84 K-20 HD that I used to haul around a 3000+lb camper with gear while towing about 3000 lbs of ski boat. That K-20 also had 3.73 gears,but had a manual transmission and a 350 that had almost as much torque as your 6.0 l but at about 1000 less rpm. Anyhow before spending the time and money on boosting, I'd try the trip to Sodac, you'll encounter grades from KY, but after all you won't be climbing the Rockies.

Thanks for the input Rog. I was just thinking the trip next year would be a lot of miles and with the hills I thought it would help in the long run. Also, thanks for the info on the trans temps. It just seemed like it climbed high very quick, guess I just wasn't expecting it... About the tow/haul button. Doesn't that just adjust shift points so the trans doesn't hit so hard under a load? Plus, my gear selector doesn't give me the option of going down one gear (unless I do it manually) Gear selection is: PNDM. (with a button on the stalk (arrow up/down) to shift manually) I could select 5th or even 4th manually but then would it shift automatically if it needed to go lower? Of course, if I felt the engine 'lugging', I could always shift lower I guess... Too many questions... Anyway, thanks for your help.

Tony, I think with a little more experience with your tow vehicle/trailer combination especially on grades you'll soon learn the sweet spot where your motor wants to be rpm wise, sometimes it'* just a matter of feel, "flying by the seat of your pants" sort of thing. I'd just keep a closer eye on the tach and shift manually to keep it in that sweet spot. As far as I know the 6.0 is a pretty stout motor so even with your mileage you'd probably be ok to boost if you're willing to shell out a few grand to pull in a higher gear or two, but I'd thoroughly research it first, one of the things would you need to start using premium gas? Back in the day, RV cam grinds were popular to bring in peak torque at a lower rpm, but I'm not even sure they're available today, even if they are then you would be looking at a host of other issues like probably getting a custom PCM tune.

These engines make power at those RPMs. I'm from the old school where 3,500 is pulling hard and 4,000 is pushing it. The LS engines are happy at 3,500-4,500 pulling. They aren't low and slow like the old days.

That said, a Chevy 350 from the 70'* pulling at 3,000-3,500 would make folks used to 50'* inlines cringe. Those would be about wound out at 3,500 let alone staying there for any length of time.

Yeah those temps are fine. A supercharger might change that quite a bit. Biggest problem the THM400 3-speed autos had behind torque-monster 454'* was heat. They'* burn up torque converters and clutches. Both have a harder time dealing with high torque low RPM than the other way around. In other words, higher RPMs leave the transmission with less torque stress to manage.

With a 5.3 and a 4L65E tow/haul actually does save the transmission a bit. Instead of: rev > computer momentarily backs off throttle > transmission shifts smoooothly > computer applies throttle . . . in tow/haul it increases line pressure and shifts quicker with little interference from the computer backing off the throttle during the shift. It also raises shift points a bit and limits how slowly the truck will hold a gear. For instance my YukonXL 5.3/4L60 will engage overdrive a little under 50MPH normal and will not engage overdrive below 60MPH in tow/haul. Prevents it from hunting. All other shiftpoints are similarly altered in tow/haul. Less torque stress this way a la my note above.

Tmbsierrahd has a 6L80 or 6L90 so:

Rev=3.064:1
1st=4.027:1
2nd=2.364:1
3rd=1.532:1
4th=1.152:1
5th=0.852:1
6th=0.667:1

. . . so yes two OD ratios but no direct 1:1 .

Like my `85 C30. I've climbed the Rockies to Eisenhower Tunnel (11,000someodd feet) a bunch of times carrying and towing 8,000-10,000 pounds in and behind it. Poor thing starts with 160HP at sea level, but has much less up high. Just patiently let it growl up the hill at around 3,300RPM usually in 1st and it'* fine. Not even enough air up there that it can do enough work to get warm.

Mine'* a 350 also, but with a THM400 auto and 4.56 gears.

Agreed.

Garageroj, your 350 was probably like my LT9: 160HP @ 3800RPM and 250lbft @ 2800RPM . . . and if I'm right tmbsierrahd has an LY6: 361HP @ 5600RPM and 385lbft @ 4400 . . . so 135lbft more at 1600RPM higher, so garageroj is pretty close. Point here is the 6.0 needs to rev higher to make even its low-end torque.

I'd say let it do its thing in tow/haul and call it good. Unless you are in a hurry that is worth thousands of dollars and a great deal of tinkering to get it all right. These transmissions are really smart these days.

How tall are these hills?

Not trying to rain on any parades, but a supercharger would likely lead to more issues in the long run.

It actually shifts a little harder under load in Tow/Haul, leading to less "in-between gears" time and driveline preservation. "Harder" but keep in mind you theoretically have more weight therefore you feel it less than empty.

I've never gotten completely used to this arrangement. I'm used to the tactile feel of shifting a lever without looking for the selected number on the dash. That said it is useful, I just find myself thinking harder about all of it. Either way, these transmissions are smart enough that I seldom worry about it unless descending a long grade or knowing I just leveled out so it will shift up a gear but I don't want it to because a new hill is almost upon us.

Think of the manual selections as a limit on how high a gear you are allowing the transmission to shift to.
- M6 is like drive, all gears available but you can change your mind by pressing the little button without moving the lever first
- M5 allows it to shift through gears 1-5 as it desires
- M4 allows it to shift through gears 1-4 as it desires
- etc.

On this platform you will never feel the engine lugging unless something is horribly wrong, so no worries there.

Hope this helps! Feel free to ask more.