Denali Sierra 2500hd 6.0 gas with 4.10

[Pappy]

I have decided to purchase the 2500HD gas. I have test driven it with the 3.73 rear end and it drove nice. I will be pulling my Classic 25 2006 with a gross weight of 8300lbs. This time of year its difficult finding a 4.10 rear end which I am convinced I want. The only way to get one is to order it. Since I have never driven one with the 4.10 rear end I am concerned that maybe I won't like the shift pattern.

Has anyone driven both the 3.73 and 4.10 or at least the 4.10 that could give me some more insight on if its as smooth shifting as the 3.73?

Does having the 4.10 noticably help slow you in the descents more so than the 3.73.

I have found some 4.10's out west but they all have the z71 package which I find rides rougher than the z85.

We like the mountains out west so we do a lot of camping there so thats our focus for wanting the 4.10.

Thanks
Pappy

[jcanavera]

Originally Posted by Pappy

I have decided to purchase the 2500HD gas. I have test driven it with the 3.73 rear end and it drove nice. I will be pulling my Classic 25 2006 with a gross weight of 8300lbs. This time of year its difficult finding a 4.10 rear end which I am convinced I want. The only way to get one is to order it. Since I have never driven one with the 4.10 rear end I am concerned that maybe I won't like the shift pattern.

Has anyone driven both the 3.73 and 4.10 or at least the 4.10 that could give me some more insight on if its as smooth shifting as the 3.73?

Does having the 4.10 noticably help slow you in the descents more so than the 3.73.

I have found some 4.10's out west but they all have the z71 package which I find rides rougher than the z85.

We like the mountains out west so we do a lot of camping there so thats our focus for wanting the 4.10.

Thanks
Pappy

Pappy while it's been some time since I bought my 2500 van, I did specify the 6 liter 4.10 rear axle combo. My heavy slide out performs well with the combo. My previous vehicle was a 5.7 liter 1500 van with a 3.73 rear axle and pulled a 6500 lb. Safari so I really can't do much on the comparison side. I use the tow/haul mode when I tow and find the shifting of the trailer is very smooth. The towing package added an external transmission cooler.

GM allows towing in OD with the combo and I pull it down a gear to hold speed on some hills here in Missouri. Shifting is very smooth and the only other thing that is interesting is that due to the axle, mileage while not towing is only a couple of MPG better than when towing. When towing I usually average 11-12 mpg.

Jack

[Steve Bryant]

I have a 2000 Yukon XL (K2500 AKA 3/4 Ton 4X4) with the Vortec 6000 4L80E transmission and 4.10 axle ratio. I love the truck and plan to keep it for a number of years to come. I ordered it new and I've had relatively few problems. The truck tows my 1991 34 foot Limited with no problems at all.

Don't think of the 3.73 versus the 4.10 as affecting the shift points. The shift points are set up in the powertrain control module on vehicles of my vintage and a transmission control module on newer vehicles. The shift points are set up the same (normal and tow/haul modes) regardless of the rear axle ratio. If you divide 4.10 by 3.73, you get 1.099. This translates to a 10 percent gain in rear axle torque and the engine RPM for a given speed is 10 percent higher too. However, the fuel mileage may be about the same because less throttle is required for a given amount of torque output.

My son has a K2500 HD Sierra with a DuraMax and Allison 1000 that he has owned since new. The truck now has about 230,000 miles on it and it is going strong.

The bottom line is that 4.10 is a good rear axle ratio for a tow vehicle. Enjoy your new tow vehicle!!!!

[dznf0g]

However, IMO, with the 6 speed and your weight, I would get the 3.73. I have driven that combo last summer with my 30'er, and was quite pleased. 4.10 would be fine, but the mileage penalty is not worth it IMO.

The guys chiming in with the 4 speed, I agree with a 4.10.....but the 6 speed keeps it in its torque range very well.

[purman]

I have a Sequoia with a 4.10 rear end with a 6 speed and the mileage difference and don't really believe is there. My friends have the 8.2 liter suburban with a 3.73. I do better down hill and better gas millage. Will mines not a 8.2 liter either. I would go with the 4.10 it's better torque and better pulling up and down hill.

[dznf0g]

Pappy lives in Indiana, not Colorado. Unless he plans a lot of mountain stuff, a 4.10 isn't needed. If he had a 34'er, I'd have a different position. With a 25'er, a 4.10 and with a 6.0 is wasteful. It'll cost 1 - 2mpg running solo (10 - 15%) and about the same percentage towing.

I have verified it in my company trucks.

[Steve Bryant]

I'm changing my recommendation. I didn't realize that the 6L90E was the standard transmission in the 2500 HD (see Powertrain Products). That trannie is rated for 550 pounds feet of torque and a gross combination weight rating of 21,000 (i.e. tow vehicle, towed vehicle, and all cargo, etc.). This transmission can be run in second, third, fourth or fifth in the hills/mountains, as required. So I'd definitely go with the 3.73:1 and just run it in a lower gear when needed. Also, I believe that the 2500 HD has a full floating rear axle, so it's even more heavy duty in design than my truck with a semi-floating rear axle. As an aside, this is one of the finest light truck transmissions on the market today...right up there with the Allisons, but of a newer design.

I know that this thread isn't dealing with towing technique, but I'll throw out some information here for any who are interested. The most efficient (economical) RPM range for towing is from about 800 to 1,200 RPMs below the torque peak up to the torque peak for a normally aspirated gasoline engine. This is also the RPM range when the engine is under a significant load that produces minimum wear and oil consumption. On the Vortec 6000 that's being considered here, the torque peak is 4,200 RPMs (see Powertrain Products) so the most efficient RPM range when towing will be from about 3,000 up to 4,200 when you're pulling like a 4% grade or steeper. On level ground, 2,500 or so would be fine.

[slowmover]

The six speed changes everything . . unless one is going to be at or near GCVWR in the worst hills or mountains. A commercial rig, IOW.

[Pappy]

Taking the information you guys have given me and taking it a little further to educate myself. I have ran some semi accurate tables. Smile

This is a comparison with the truck I have now vs new truck.

New truck
2500HD Chevy 6.0 Gas
3.73 axle 4.10 axle
1st 4.03 15.0 16.5
2nd 2.36 8.8 9.68
3rd 1.53 5.26 6.27
4th 1.15 4.29 4.7
5th .85 3.17 3.48
6th .67 2.49 2.75

Old truck
Nissan Titan 5.6 gas
2.94 axle 3.35 axle
1st 3.83 11.26 12.8
2nd 2.37 6.96 7.94
3rd 1.52 4.46 5.09
4th 1.0 2.94 3.35
5th .83 2.44 2.78

Both truck engines develope the same Torque
The Chevy has about 43 more HP.

It appears to me that either axle on the Chevy will out perform
what I have now in the lower range. But it also appears that the
higher gears or almost identical practically speaking so I can't see
where the 4.10 would really drink any more fuel at cruise than
the 3.73. I know I have left out important things like engine torque
curve but from what I have seen the Chevy peaks about 4200 and
the Nissan about 3600 both having at least 90 percent around 2000
rpm. I thank everyone for their input but I think I will go with the
4.10 unless I have missed something. The only thing I don't want to
see is below 10mpg pulling that would really bum me out as the kids
say. The Titan has always delivered about 10.5 plus in the last 50,000
miles but its time for some more payload and cruise control. I am tired
of working a weight & balance before each trip and my wife wants
her cruise control back. Smile

Pappy

[Wayward]

I have always used very low ratio axles for towing mostly to improve the shift points and keep the engine in its torque range. I went with 4.30 gears in my f150 and it was the best mod I made for towing. However my experience with this the new 6-speed in my 2011 F250 has caused me to rethink things completely.

The transmission control software is very sophisticated and specifically designed for towing. With the trailer plugged in, it adapts the shift pattern based on the incline (up or down), road speed, throttle position, brake pressure, and engine response (load sensing). And...it all works just as smartly on cruise control with the Airstream in tow.

I was planning to have the dealer swap in 4:10 Ford gears after buying the F250 new. With 6 speeds, a big fat torque curve, and engine/tranny software that always picks the right gear at the right time, I happily cancelled that mod.

I also pull a 10,000lb utility trailer load occasionally which might-could use 4:10 gears but not badly enough to swap.

I suggest you get the 3.73 if you like the truck, tow for a while and then decide. You can always change the axle gears later. Simple job for any shop.

If you do go with 4.10, I would not worry about gas mileage. In my experience swapping to lower gears, gas mileage improves slightly towing and is about the same not towing if I avoid the urge to indulge in the faster takeoffs

[dznf0g]

Originally Posted by Pappy

Taking the information you guys have given me and taking it a little further to educate myself. I have ran some semi accurate tables. Smile

This is a comparison with the truck I have now vs new truck.

New truck
2500HD Chevy 6.0 Gas
3.73 axle 4.10 axle
1st 4.03 15.0 16.5
2nd 2.36 8.8 9.68
3rd 1.53 5.26 6.27
4th 1.15 4.29 4.7
5th .85 3.17 3.48
6th .67 2.49 2.75

Old truck
Nissan Titan 5.6 gas
2.94 axle 3.35 axle
1st 3.83 11.26 12.8
2nd 2.37 6.96 7.94
3rd 1.52 4.46 5.09
4th 1.0 2.94 3.35
5th .83 2.44 2.78

Both truck engines develope the same Torque
The Chevy has about 43 more HP.

It appears to me that either axle on the Chevy will out perform
what I have now in the lower range. But it also appears that the
higher gears or almost identical practically speaking so I can't see
where the 4.10 would really drink any more fuel at cruise than
the 3.73. I know I have left out important things like engine torque
curve but from what I have seen the Chevy peaks about 4200 and
the Nissan about 3600 both having at least 90 percent around 2000
rpm. I thank everyone for their input but I think I will go with the
4.10 unless I have missed something. The only thing I don't want to
see is below 10mpg pulling that would really bum me out as the kids
say. The Titan has always delivered about 10.5 plus in the last 50,000
miles but its time for some more payload and cruise control. I am tired
of working a weight & balance before each trip and my wife wants
her cruise control back. Smile

Pappy

Well, hate to rain on your parade, but towing my 30'er with toys in the bed (about 15,700 GCW) I saw 8.5 - 9.5 MPG on a regular basis. A couple of times, I saw near 10. You MAY hit 10 more regularly with a 25'er, but I still say you won't with a 4.10. But, get what makes you happy. That's what really matters.

[Pappy]

A few last thoughts on this subject. I did give the 3.73 some more thought since there are units available to buy locally. But when I look at the Gross combined weight limit of only
16,000 lbs it just doesn't seem like enough to make the move worth
it when considering just the weight limitations. Thats only 900 more pounds than what I have now. Now maybe the engineers are being conservative but I have to go by the placard. So if I load the airstream and the truck the way I want to that leaves me with only 400 lbs to the good. Not exactly the margin I was looking for. The salesman told me that if I order now I won't get it until the first week in October. Seems
like quite a slow build time plus if you order you get no incentives $$.
The salesman told me the only change from the 2012 model and 2013 is
that you will no longer be able to deselect tow haul mode to stop the
transmission braking as some say they do while pulling in the flats. You will
still be able to select tow haul but it will no longer have effect over the
engine braking. I really didn't like the sound of that. But since he has not been very knowledgable on his product he may have got that wrong. I hope so.

Pappy

[ZoomZoom]

My 2007 AWD Denali is a 6.2 all aluminum block 386HP 403FP torque with the tow selection option and 6 speed, it greatly changes the shift points and affects engine braking, sounds odd but I actually get better mileage towing a 1960 24'
Greg

[Silvertwinkie]

Though I have towed about a ton less than you with both 3.73 and 4.10, and transmissions have changed quite a bit since 1996 and 2004, I will say that 3.73s will do the job, 4.10 will be nicer to the tranny. I hear a number of folks say that 4.10s will eat gas like there is no tomorrow and I caravaned with folks that had a similar size and weight Airstream, towing with the GMC version of my 2004 Suburban 2500 (6.0L). We filled up, we went the same distance...their truck with 3.73s and mine with 4.10s. The MPG difference was undetectable.

I don't think in GM land you can get 4.10s with diesel, but if I found a gasser that had 4.10s I would grab that. Sweet spot on mine is about 2000 rpm, which is about 60-62mpg and according to the DIC, I get about 11 to 12 mpg towing. Had a good tail wind last trip and got upward of 15mpg!

If towing in mountains and hills are in your future, the 4.10s will play nicer with your truck. I love my 04 2500 Burb with 4.10s. Can't get 'em anymore.

[slowmover]

Originally Posted by Pappy

A few last thoughts on this subject. I did give the 3.73 some more thought since there are units available to buy locally.

But when I look at the Gross combined weight limit of only
16,000 lbs it just doesn't seem like enough to make the move worth
it when considering just the weight limitations. Thats only 900 more pounds than what I have now. Now maybe the engineers are being conservative but I have to go by the placard. So if I load the airstream and the truck the way I want to that leaves me with only 400 lbs to the good. Not exactly the margin I was looking for . . . .

Pappy

Your thoughts on the 4.10's make sense.

While the 4.10's aren't as attractive as in years past -- and so long as solo mpg is otherwise acceptable (as is increased engine wear) -- then hold out for what you want. GM gives big credence to the gear change for increased GVWR, etc., so that is a good line to follow short of reducing the load.

.

[dznf0g]

Pappy, are you really that heavy with your 25'er?

[Pappy]

dnzf0g,

The Gross on the Classic 25 2006 is 8300 lbs. Its never been that heavy because
of my Tow vehicle limitations. But if I let the wife load it without supervision well!

Pappy

[dznf0g]

Originally Posted by Pappy

dnzf0g,

The Gross on the Classic 25 2006 is 8300 lbs. Its never been that heavy because
of my Tow vehicle limitations. But if I let the wife load it without supervision well!

Pappy

You might want to run it across the scales. My GVWR is 10,000, but fully loaded (ceramic dishes and a LOT of stuff, a little water in the tank) I'm at 8,500 lbs with empty weight 7260. I run with a scooter, an inflatable 11' boat, 10 hp motor, gas for boat.....

I really struggle with the thought that you'll be at 16,000lbs (or that close). Have you scaled it?

[Pappy]

dznf0g,

I have put it on the CAT a couple of times and the way it was loaded at that time
put it at 7300 lbs. The Sierra 2500HD gas sticker weights were all around 7200 lb range that would bring it up to 14700 with out my wife and the kitchen sink. Smile
Its that Kitchen sink that will finish off the rest of the payload.

Pappy

[Steve Bryant]

Pappy,
If you're more comfortable with the 4.10:1 axle ratio, by all means go for it! As I mentioned in my first post, the gas mileage won't be 10% lower, nor will the engine wear be 10% greater. I'm based my recommendation on the fact that with a six speed transmission, an engine with a flat/broad torque curve and the fact that the torque converter will unlock when it needs to for additional torque multiplication; the transmission control module will find a sweet gear ratio for virtually any situation.

Your thinking on GCWR has merit and you are the person who's buying the truck. I wish you many miles of trouble-free driving!

All my best,

Steve