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Author Topic: TOWING WITH 2500  3.73 Vs 4.10 Gears  (Read 24800 times)
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MrBill
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« on: 05/16/02 03:09 PM »

The 2500 makes an excellent high end towing machine. I know when I ordered my Avalanche I had a choice of gears 3.73 Vs 4.10. I will explain what I chose and why.

The Vortec 8100 V8 SFI engine in the Avalanche 2500 delivers 340 horsepower @ 5200 rpm and 455 lb.-ft. of torque @ 3200 rpm.

Below is what you can tow. Depending upon you configuration.

8.1L with 3.73 gears can tow 10,100 lb. or with 4.10 gears you can tow 12,000 lb.

My travel trailer is 34 feet long and weighs 6,354 lb. With an axle weight of 4,644 lb.

I chose the 8.1L with the 3.73 gears. The reason was simple. With all that horse power you can easily move a trailer as large as mine. You will get better gas mileage because of the lower RPM. Let me explain I will keep it very simple. This is just an example so please excuse me if I am off by a few hundred rpm.

Say you are traveling at 60 mph. The RPM with the 3.73 gears should read around 2200, With the 4.10 gears you will see the RPM around 2500. You say not a big difference, Try traveling 4,000 miles in one trip. You can see the dollars you can save.

Mr. Bill

P.S. Always use the Tow/haul button when towing.
« Last Edit: 05/17/02 07:02 AM by MrBill » Logged

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« Reply #1 on: 05/16/02 07:41 PM »

That was a damn good explaination....you got my attention.....and after yesterday morning....I recommend driving in tow/haul mode very very often...
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« Reply #2 on: 05/17/02 02:29 AM »

Do I really need the tow/haul on when I'm towing a 700lb boat and trailer over flat terrain?  I don't think so, but I'm no expert on this.

It would seem that the tow/haul would be more useful on heavier loads (i.e 3000lbs and up).

Trash
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« Reply #3 on: 05/17/02 06:47 AM »

Trash

I have towed travel trailers and boats for over 25 years now. I will tell you this, The new tow/haul button on our AV is the best thing chevy has come up with yet. Let me explain.

You have an automatic transmission with overdrive. The overdrive is used for better gas mileage. If you tow using overdrive the transmission will continue to shift up and down, putting a strain on the tranny. The transmission will heat up a lot faster and all the clutches in the tranny will start to wear. You may not notice it right away, but you are putting wear and tear on the tranny.

The old rule of thumb was to put the shifter in 3 drive when towing. The tow/haul button does something like that. But it uses sensors to determine the load you are hauling and then reprograms the transmission.

If you are hauling 700 lb. or 7000 lb. use the Tow/haul button. It will save you problems in the long run.
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« Reply #4 on: 05/17/02 07:04 AM »

Here is a quote from the Owners Manual:

Operating the vehicle in tow/haul when lightly loaded or
with no trailer at all will not cause damage. However,
there is no benefit to the selection of tow/haul when the
vehicle is unloaded. Such a selection when unloaded
may result in unpleasant engine and transmission
driving characteristics and reduced fuel economy.
Tow/haul is recommended only when pulling a heavy
trailer or a large or heavy load.

I'm not trying to pick a fight or anything, but it seems to me that tow/haul mode is recommended only on heavier loads.  I can't believe that 700lbs is in that category.  Especially since my towing terrain is flat as a pancake around here.

On another note, as I was putting the hitch in the receiver the other day, I noticed a decal on my hitch frame that says "max trailer weight 5000lbs".   Huh I thought a 1500 series Avy can tow 7500lbs?  What gives.

The ever confused....

Trash
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« Reply #5 on: 05/17/02 09:48 AM »

Trash

Sorry to confuse you. The tow/haul option I mentioned is my personal preference. I have had several tranny and rear axle problems with my trucks in the past. Everytime I get it fixed the dealer would tell me it is better to be safe than sorry. Again my personal preference. There is another topic I have listed below.

http://www.chevyavalanchefanclub.com/cafcna/index.php?board=19;action=display;threadid=8761

Now the hitch rating. I will make some comments that may be my personal feelings. The limits you see on your hitch should read:

This is what my 2500 AV hitch says.          

Standard: Tongue Weight 600    Max. Trailer Weight 5000
Weight Distributing: Tongue Weight 1500  Max. Trailer Weight 12000

Chevy Says:

1. Avalanche 1500 2WD, The North Face Edition and Z66 models equipped with the available 4.10:1 ratio rear axle can tow up to 8,300 lb., and 4x4 models up to 8,100 lb.
2. Avalanche 1500 2WD, The North Face Edition and Z66 models equipped with the standard 3.73:1 ratio rear axle can tow up to 7,300 lb., and 4x4 models up to 7,100 lb.
3. Avalanche 2500 2WD and 4x4 models equipped with the available 4.10:1 ratio rear axle can tow up to 12,000 lb.
4. Avalanche 2500 2WD models equipped with the standard 3.73:1 ratio rear axle can tow up to 10,400 lb. and 4x4 models up to 10,100 lb.

Since my trailer weight 6,354 lb. And I use a weight-distributing hitch. The class III hitch is fine.When Chevy talks about the MAX towing weight they always talk about it using the weight-distributing hitch. This is GM covering their butt. Yes your truck has the capability to tow 7300 lb. if you use the weight-distributing hitch. Without weight-distributing hitch the MAX is 5000.
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« Reply #6 on: 05/18/02 04:09 PM »

I have a 5.7 liter Silvarado with 4:10's and it turns about 2200 RPM at 65 MPH.  My trailer weighs over 8000 lb when loaded and my truck will only pull it about 63 MPH and that is in third gear.  In OD the transmission won't lock with the trailer.  (By the way, tow/haul doesn't come into play at freeway speeds.)

Does anybody think that anything less than a 2500 Avalanche with 4:10's will work for me?  I have to tow up the Sierra Nevada or Coastal Mountains on all my trips.
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« Reply #7 on: 05/19/02 01:50 AM »

I had a Chevy Tahoe Z71 with the 5.7L and 4.10 gears. Real nice truck. Towing with it was a problem. On flat surfaces it was OK, but when it came to hills the motor and transmission real heated up. I was pushing this truck farther than I wanted.  Thats why I went with the 2500 AV with 3.73 gears. On my last trip from Buffalo NY to Orlando FL we went up and down the hills in PA and WVA with little strain. I was very impressed how well this truck hauled my trailer.

As for you situation I think you are correct in saying you will need a 2500 with 4.10 gears.  That will be more than enough power. The 2500 with 3.73 gears would do the trick, but you would be working it a little harder. This is just my personal option. It all depends on you driving style. Only you can decide.  
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« Reply #8 on: 05/19/02 03:47 AM »

I have a 5.7 liter Silvarado with 4:10's and it turns about 2200 RPM at 65 MPH.  My trailer weighs over 8000 lb when loaded and my truck will only pull it about 63 MPH and that is in third gear.  In OD the transmission won't lock with the trailer.  (By the way, tow/haul doesn't come into play at freeway speeds.)

Does anybody think that anything less than a 2500 Avalanche with 4:10's will work for me?  I have to tow up the Sierra Nevada or Coastal Mountains on all my trips.


Your present RPM speed numbers match my last three vehicles with 4.10 gearsets.  I have the 4.10s in my 2500 AV.  Would not consider anything else to pull a 8000# trailer any distance at all. Will be a lot easier on vehicle and the driver over the long haul. You may give up 1 MPG empty but will make it up while towing. (You will not have to bury pedal as much or as often.)
« Last Edit: 05/19/02 04:32 AM by orboater » Logged
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« Reply #9 on: 05/19/02 08:03 AM »

Talking about towing 3000# bass boats, I've had a 454 and a V-10 that yanked pretty good but still liked to tow in 3 instead of OD. Early tests seem to show my buddy's 2500 4.10 AV to be the only gas truck I've seen that would pull in overdrive through hilly terrain and not over downshift. I've been curious if a 3.73 would also be able to do that.  I'm wondering if the 4.10 keeps the R's just enough higher to be able to stay in OD and if the 3.73 would call for power more and want to downshift more often causing you to want to run it in 3. If that theory were true then the 4.10 would actually be the economical choice. (Hope I phrased that where it made sense)
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« Reply #10 on: 05/20/02 02:50 AM »

Talking about towing 3000# bass boats, I've had a 454 and a V-10 that yanked pretty good but still liked to tow in 3 instead of OD. Early tests seem to show my buddy's 2500 4.10 AV to be the only gas truck I've seen that would pull in overdrive through hilly terrain and not over downshift. I've been curious if a 3.73 would also be able to do that.  I'm wondering if the 4.10 keeps the R's just enough higher to be able to stay in OD and if the 3.73 would call for power more and want to downshift more often causing you to want to run it in 3. If that theory were true then the 4.10 would actually be the economical choice. (Hope I phrased that where it made sense)


AMEN ! Wink
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« Reply #11 on: 06/18/02 04:42 PM »

MrBill-

I believe that in OD with 4:10's the RPM should be about 2200 @ 60MPH.  That is what it is in my '91 2500 PU.  In drive (3rd) it turns about 2800.  Maybe the transmission is different in the Av but it has got to be less than 2500 RPM.

Gandolph?
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« Reply #12 on: 06/18/02 05:40 PM »

Here is a great post by MarkD from 3.73 vs 4.10 - getting off the line

may be stating the obvious, but I think of it this way...

(these are just arbitrary numbers to make the math easy)

Assume your engine puts out the following torque numbers...
         1st gear speed w/  3.73's  4.10          
1000 rpm --------- 450 ft/lbs      10     9
2000 rpm --------- 500 ft/lbs      20    18
3000 rpm --------- 600 ft/lbs      30    27
4000 rpm --------- 650 ft/lbs      40    36
4445 rpm --------- 675 ft/bls      45    40
5000 rpm --------- 700 ft/lbs      50    45

(yeah,yeah, I know, read disclaimer above)

If it takes the following power levels to hold a steady speed

10mph -------------200  ft/lbs
20mph -------------220  ft/bls
30mph -------------240  ft/bls
40mph -------------260  ft/bls
50mph -------------280  ft/bls

(remember, these are the official numbers of thin air, because that's where I pulled them from)

Ok, let's look at 40 mph

260 ft/lbs required to maintain 40mph
3.73's put rpm at 40mph at 4000 rpm, and 650 ft/lbs
4.10's put rpm at 40mph at 4445 rpm, and 675 fl/lbs

That leaves 390 ft/lbs at 40 mph to accelerate with 3.73's
Where there is 415 fl/lbs available with 4.10's

So in this case , you would have 25 fl/lbs more available at 40mph.  Of course this benefit would apply throughout the entire rev range.
Grin

From another expert, Oxidizer - @ 80 mph

3.73 = 2200 rpm
4.10 = 2450 rpm
4.56 = 2700 rpm
« Last Edit: 06/18/02 05:47 PM by gandolphxx » Logged

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« Reply #13 on: 06/18/02 06:01 PM »

I have not been an avid Chevy truck fan, however, after going through my third rearend on my Dodge 1500 Sport 4x4 I decided to seek new transportation.  Ford is out of the question, so I bit the bullet and went to Chevy.  To cut the story short, I am now the PROUD owner of a 2500 AV 4x4.  I pull a 22 ft bass boat from Kansas City to Southern Missouri.  My Dodge was forever downshifting gears when I hit the hills.  I got terrible gas mileage, 9-10 MPG, when towing. Yesterday I towed my boat for the first time with my AV and it did not downshift one time.  I drive on average 75 MPH and I still got 11 MPG.  I attribute this to my 4:10:1 rearend. What I'd like to know is what makes a 4:10 a better towing rearend than the 3:73 or 3:55. And was this the reason my rearend kept going out on the Dodge. Smiley
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« Reply #14 on: 06/18/02 06:18 PM »

Bassmaster, my post above should answer most of the questions, HP & Torque are the hallmark of the 8.1L - combine that with the 4.10 gears in that monster 14 bolt corporate 10.5" differential and you have it. Grin
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« Reply #15 on: 09/29/03 08:59 AM »

Quote from: BassMaster
What I'd like to know is what makes a 4:10 a better towing rearend than the 3:73

The 4.10 is a full-floating axle type. The 3.73 is a semi-floater. This makes the 4.10 a much stronger design. The actual drive axle does not carry the weight of the truck on a FF design; the axle housing carries the weight. On full-floaters you can twist the axle in two and the wheel will not fall off as it would on a semi-floater. Look at the medium duty trucks going down the road and you will see they are all the FF design.
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« Reply #16 on: 09/29/03 09:44 AM »

The 4.10 is a full-floating axle type. The 3.73 is a semi-floater. This makes the 4.10 a much stronger design. The actual drive axle does not carry the weight of the truck on a FF design; the axle housing carries the weight. On full-floaters you can twist the axle in two and the wheel will not fall off as it would on a semi-floater. Look at the medium duty trucks going down the road and you will see they are all the FF design.


HUH.....The rear ends and the axle are the same....all they have done was offer two differential ratios (input RPM of the differential versus axle shaft RPM)

3.73 input RPMS equal 1 axle shaft (tire) RPM

or

4.11 input RPMS equal 1 axle shaft (tire) RPM

the 4.11 requires higher driveshaft (Engine) RPMs for the same MPH as compared to the 3.73.....




« Last Edit: 09/29/03 09:44 AM by ygmn » Logged

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« Reply #17 on: 09/29/03 10:22 AM »

ygmn: unless they have very recently changed, sorry the 3.73 and 4.11 are not the same. Look at both with the covers off and you will see what I mean.

As far back as 94 when I bought my 2500 Suburban and again in 02 when I bought my Av, the 3.73 was a semi-float and and 4.10 was a full-float.

For those who are unfamiliar with the physical appearance - on SF axles, the end of the axle is essentially flush with the wheel itself, on FF the axle extends some 3-4 inches outside the wheel.
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« Reply #18 on: 09/29/03 10:29 AM »

ygmn: a second thought. After I posted I noticed you have a 1500 series. There may be the difference! MAYBE on the smaller 1500 differentials there is no physical difference between a 3.73 and a 4.10 other than the ratio itself. I would be surprised to ever see a full-floating axle on a modern 1/2 ton truck. Again, unless things have changed what I said does apply for 3/4 ton GM trucks.
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« Reply #19 on: 08/03/04 09:30 PM »

Sorry about getting off subject. I just purchased an 02 AV 2500, how can i find out which gear set up I have, the 3.73 or the 4.10??
I doubt I'll be towing anything of sizable weight as of yet, but I would like to know what I've got. This is the first I have heard of the "gears". Thanks for any help. Love the Fan Club, everyone is very helpful. Kramer
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« Reply #20 on: 08/05/04 10:50 AM »

Orboatr-

Get the 4.10, with an 8000 lb trailer pulling at 65 mph should be about 2200 rpm good torque w/ the 8.1.

Kramer1354: Build sheet in glovebox will have either a GT4 or GT5 code. The GT5 is the 4.10.

Avalon
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« Reply #21 on: 08/09/04 04:14 PM »

THANKS FOR THE HELP!!!!
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« Reply #22 on: 08/09/04 04:53 PM »

ygmn: unless they have very recently changed, sorry the 3.73 and 4.11 are not the same. Look at both with the covers off and you will see what I mean.

As far back as 94 when I bought my 2500 Suburban and again in 02 when I bought my Av, the 3.73 was a semi-float and and 4.10 was a full-float.

For those who are unfamiliar with the physical appearance - on SF axles, the end of the axle is essentially flush with the wheel itself, on FF the axle extends some 3-4 inches outside the wheel.


Sorry, Big Block. I know my new 2500 w/3.73 has a full-floating axle.

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« Reply #23 on: 09/18/04 08:44 AM »

Different hubs or brakes will move the axle ends out farther so the best way to tell is that the full floater has bolt-in axles. Under the center cap you will see the end of an axle held in by 8 small bolts. If no 8 bolts, then the axle is held in at the differential by a C-clip. Full floater is far stronger, but C-clip is more than strong enough. I have plowed snow, hauled too much weight, off roaded and burned (35 inch) tires off, and I never broke my 14 bolt 4.10 Detroit Locker semi-floater. I now have another 4.10 full floater, and I havent been able to breeak that either.
I didnt know that the full floater may or may not be an option on the Av 2500, but I will be sure to check when I start shopping for a used one.
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« Reply #24 on: 09/21/04 09:24 PM »

I am looking at buying a 04 av and not sure if i should get the 1500 with 4.10 or 3.73 or the 2500 .

I have a 29 foot holiday trailer that I would like to pull once every year or 2 from or lake lot to a holiday destination.  the trailor ways 5300 lbs unloaded


Any Thoughts

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