GM 6.0 gear searching.....

[ericpatt]

Help??

While this may have been covered to some extent on this forum or another, I'm looking for suggestions for my 2012 Suburban 2500 with the 6.0l engine.

Towing my boat(04 Nautique) it's awesome. Hardly know the boat is there.

However, when hauling our 30ft camper it's a different story. Camper weighs 6900lbs empty. Fully loaded it's probably close to 8000 not including wife, 3 kids, dog and misc stuff in the truck. Can't keep it 60-65 without it searching for a gear it "likes". I usually downshift manually but tach is constantly at 3k.

What to do? Love the truck. Kids are happy in back and plenty of space. Called a couple shops.
1 suggestion was to modify computer?
2 suggested cold air intake, tuner, & exhaust?

Does any of it work??

There's got to be something I can do. Slowing down only makes me feel like a traffic hazzard. Would like to be able to pull at least 65mph on the highway....

[APT]

Good explanation, parker.rowe. While I understand the math well, my point is that 10-15% more wheel torque may not be enough for OP's exact situation, and even less likely worth $2-3k. 5th gear to 4th gear ratio is 0.85->1.15, plus the 500rpm jump closer to peak torque of the 6.0L. That's free, a button click M5->M4.

I'm with intheburbs. Let it rip. The powertrain is 2500HD designed for far more abuse than recreational RV towing.

[parker_rowe]

APT wrote:
4.10 will just mean 2200rpm at 65mphh is now 2420rpm. That will allow some situations where 5th gear will hold longer. However, 4th gear is now 300rpm higher. I'm not convinced that will be helpful enough to justify $2000-3000. $600 for a custom Black Bear tune will not likely provide much more increased torque at 2200rpm (less than 10% of gearing), but I have heard it greatly improves normal shift programming.

Changing gears does more than simply change the cruising rpm though.

To make it simple...say you are putting out 100 ftlbs of torque, through a 1:1 ratio gear in the transmission with a locked converter, with a 3.73 rear.

That is 373 ftlbs to the axles.

Change to 4.10's.

You are now at 410ftlbs feeding the axles.

So you gain 300rpm to put you closer to the power range you want, and you gain 37 ftlbs to the axles. And this multiplication happens across the entire rpm range.

Say you open the throttle more going up a hill and you are putting out 200 ftlbs or torque.

3.73s : 746 ftlbs
4.10s: 820 ftlbs

74 ftlb difference...gears MULTIPLY the torque to the next thing behind them.

This is a very simple example to show how gear multiplication works for those that don't know.

If you can deal with the rpm, there is no cheaper way to boost torque to the rear wheels in gas truck.

With a engine that makes power at higher rpm like a 6.0, and a double overdrive 6 speed, I would add more gear in a minute! Doubt it will affect towing gas milage, might even help. But when I tow, I worry less about mileage and more about the truck doing what I want.

[intheburbs]

ericpatt wrote:
Thanks everyone!

Correct. It has the 3.73 and i do use the tow/haul mode. Just double checking cause 3k seemed high as this was the first "big" thing I've towed outside of boats and snowmobiles.

Took a trip last year to Smokey Mountains. Got really nervous when trans started heating up through the hills(~200). Have made it a practice to have it flushed and new filter before long trips. Live in Wisconsin. Heading to Kentucky this spring break.

Had heard that GM was going to put diesels back in surburbans. Might be happening for 2019?? Don't know if i can stomach $80-90k though.....

Chuckling at the part in red.

It's a 3/4-ton truck designed for towing, not a fragile half-ton. Lock it in 4th, and let 'er rip. The 6.0 loves to rev.

This is from our last trip out West, climbing Powder River Pass, elevation 9666 feet, with a GCW right around 16,000 lbs.



And on the way down, I was spinning the engine so fast for engine braking, that I actually spun the A/C belt off the pulley without it breaking. When I got down, I pulled over, popped the hood, and saw the belt hanging from the crank pulley. I'd thought I'd killed the compressor by spinning it so fast.

I also saw similar trans temps the last time we were in Colorado, running it through the "Ike Gauntlet," aka the Eisenhower Tunnel, elevation 11,158 feet.

And, BTW, Dex6 can handle some pretty high temperatures. The "trans hot, idle engine" message/warning only comes on at 265°.

My truck has 175k miles, is all original, I beat the **** out of it, and I've spent a total of $23 in repairs over the last 4 years, to replace a bad purge valve solenoid.

ETA: And for the record, the word I used was c rap, not some really bad swear word. 🙂

[jodeb720]

I have a 2003 2500hd with 4.10's and a 4l80e trans (4 speed). They don't begin to produce any power until they are above 3000 RPM.

When climbing the transmission has a tendency to upshift - about 300-400rpms when I want the RPM's around 3000. I find if I take my foot off the throttle and then step back down, it overrides the half shift (as I call it) and then stops hunting. It also puts me back in control of the RPM's around 3000+.

I've asked on other forums but nobody seems to know how GM has the transmissions electronic rules tied to it.

Maybe someone on here knows.

I put a 16 pass stacked plate, electric fan assisted cooler on the transmission - and per lawrosa - I should be above 175 climbing; However, On a long hill climb I generally will end up with about 200-220 for trans temps.

Don't flush your transmission!!!

Have your mechanic drop the trans pan cold, then clean it and replace the filter. Then you can have the remaining 10 quarts swapped through a flush.

Most of the time,the flush will stir up the particulate matter inside the transmission and wear things out prematurely. It's more expensive, but worth it (or you could do it yourself).

I do this annually generally after I do the trips (that way if something does get into the transmission, I don't find out about it on the road).



I've got over 160k on my Trans towing and it's in good shape.

[GeoBoy]

I had an 05 Silverado 3500 with a 6 liter and 3,000 rpms are fine. I removed the small transmission oil cooler and installed a Tru-Kool 40k transmission cooler in it’s place and never saw transmission temps over 175 degrees climbing the Rockies pulling my AF TT out west.

[APT]

4.10 will just mean 2200rpm at 65mphh is now 2420rpm. That will allow some situations where 5th gear will hold longer. However, 4th gear is now 300rpm higher. I'm not convinced that will be helpful enough to justify $2000-3000. $600 for a custom Black Bear tune will not likely provide much more increased torque at 2200rpm (less than 10% of gearing), but I have heard it greatly improves normal shift programming.

[anw7405]

I agree with most on here. The 6.0 has to rev to make power but it doesn't hurt it at all. Lock out 5th and 6th and let er eat. Just watch your temps and you will be fine. there just isn't any new options when it comes to 3 rows of seats and towing heavy. I hate that!

[lawrosa]

As far as the trans goes 200f aint that bad... But I would invest in adding a second cooler in line with the factory cooler..

I installed the biggest cooler I could fit...And lowered the factory cooler to get it out behind the chevy bowtie on the grill.



Here is pulling the smokey mountains. 230f coolant temps, but 175f tranny temps..

1st gear, 3500 rpms, 30 mph....lol... Hey its only a 4 speed!!!!!

Just a note: I could easily speed up.. But chose to pull these hills sitting @ 3500 rpm.. Its a good power band and the 5.3l will pull all day I believe.

Ran with A/C on the whole trip... The A/c on keeps the fans on. helps cool better.

Video...

https://www.flickr.com/photos/93289479@N04/35822079640/in/datetaken/

[PDX_Zs]

goducks10 wrote:
All GM 2500 trucks now come with 4.10 standard. Must be a reason.

Check the tire diameter on the new trucks compared to the old Suburbans.

You may find it equivelant.

😉

[goducks10]

All GM 2500 trucks now come with 4.10 standard. Must be a reason.

[ericpatt]

HA! Yes, can't remember if a school bus passed us out there but we were crawling. Felt like it was the little engine that could. Seriously, crawling up some of those hills.

[wowens79]

Like others have said lock it in a lower gear. I've got the same motor, and gearing, but with just a 4spd tranny, and pull about the same weight. If it is rolling, or hills, I just drop her to 3rd, and it turns 3k, and pulls great.

I did get down to 1st gear and 28mph going over the Smokies from GA to G-burg. I got passed by school bus. It was kinda embarassing 🙂

[Iraqvet05]

Cold are intakes in my experience are a waste of money. I will also second Black Bear Performance tuning but don't know how he does tunes for the newer GMs. I ordered a reprogrammed ECM from him then had to find someone local with the correct scan tool to do a crank relearn but it really woke the truck up.

[ericpatt]

Thanks everyone!

Correct. It has the 3.73 and i do use the tow/haul mode. Just double checking cause 3k seemed high as this was the first "big" thing I've towed outside of boats and snowmobiles.

Took a trip last year to Smokey Mountains. Got really nervous when trans started heating up through the hills(~200). Have made it a practice to have it flushed and new filter before long trips. Live in Wisconsin. Heading to Kentucky this spring break.

Had heard that GM was going to put diesels back in surburbans. Might be happening for 2019?? Don't know if i can stomach $80-90k though.....

[PDX_Zs]

How upsetting is this too you in real dollars?

I have the same truck and am asking myself the same question. The stock truck is really fine, and can do anything I need it to do. It's just a bit "busy" doing so.

For me the answer was that any tunes or gear changes are just very minor improvements. Check out Whipple superchargers, and see what you think. 400+ hp is a noticeable difference...

🙂