Gears

[Joe28443]

Here is my question. I have a 03 with a 5.3 stock 3.42 gear, I am changing the gear in it and I am hearing that 4.10 may be to low. I need all the pull I can get due to pulling 6500# TT. Pulling it a few times a year, Do I need a 410 or 373. What gear do you have , engine size and what does it tach at 70mph? thanks

[xsports33]

get 4.10 if you're concerned about towing power. 3.73's won't be that much of a difference from 3.42's. I have 4.56's, but i also have 35" tires which brings my effective gear ratio close to 4.10. I also pull a 4500 lbs boat during the summer.

 

There are online calculators that you can figure out your RPMs based on tire size and gears.

[pm26]

Pulling a 6,500 lb trailer long distances is pushing it to the limit. Definitely 4.10s and a good transmission cooler. And an oversize rear differential cover made of ribbed aluminum is helpful too.

[cmoore74]

Very easy to determine RPM's for a gear change if you have a base-line.

 

Multiply your current RPM at 70 MPH by 3.73/3.42 to determine new RPM at 70 MPH for swap to 3.73's. Likewise multiply your current RPM at 70 MPH by 4.10/3.42 to determine new RPM at 70 MPH for swap to 4.10's.

 

I too unfortunately have the 3.42's. At 70 MPH I'm at about 1850 RPM in 4th gear. So with 3.73's the RPM would be about 2000 RPM. With 4.10's the RPM's would be about 2200 RPM.

 

I tow a 4000 lb boat and I'm wishing I had gotten the 3.73's. I think if you're towing 6500 lbs you'd be better suited with 4.10's.

[StoneyPgh]

I have a 03 with a 5.3 stock 3.42 gear, I am changing the gear in it and I am hearing that 4.10 may be to low. I need all the pull I can get due to pulling 6500# TT.

You'll need the 4.10 gears to pull that load with a 5.3L engine.

[pm26]

The additional problem with TTs is that they have a large front sail area and that makes pulling thm a lot harder on the tow vehicle due to substantial wind resistance. A low 6500 lb trailer would be a lot easier to pull.

 

I have 3.73 gears and the RPMs at 70 MPH in 4th gear are about 2k.

[thecraft]

get 4.10 if you're concerned about towing power. 3.73's won't be that much of a difference from 3.42's. I have 4.56's, but i also have 35" tires which brings my effective gear ratio close to 4.10. I also pull a 4500 lbs boat during the summer.

 

There are online calculators that you can figure out your RPMs based on tire size and gears.

Completely agree... you can go to www.4lo.com for gear ratio calculators.

[Gozer]

No question on going to 4.10's with the 5.3L. I'm pulling similar weight travel trailer with NBS 6.0L with 4.10's. There's plenty of power for pulling mountains in PA/NY, but the 6.0L certainly screams down into 3rd and sometimes 2nd to maintain 55~60mph. It would scream even more with higher gears.

[wlvrn1215]

I have a 03 with a 5.3 stock 3.42 gear, I am changing the gear in it and I am hearing that 4.10 may be to low. I need all the pull I can get due to pulling 6500# TT.

You'll need the 4.10 gears to pull that load with a 5.3L engine.

 

 

 

 

I have 3.73's and have no problem towing 6000+ with my 5.3. For gas milage and towing if you don't do a lot of towing then 3.73's are the way to go.

[C & A s Dad]

Joe, I am going to agree 100% with Pete here. I am towing a 29' 6500 lb TT with an '02 5.3 Yuk XL 4.10s. I almost did not buy the truck due to the 4.10s and I wanted 3.73s. I am very happy the 4.10s are back there now. The weight and frontal area drag is significant on such a small Cu In engine and your engine likes to rev to make it's power. My sweet spot comes in around 2100 on up and as long as I am pulling in that range, I have plenty of tq. Let it drop to 1800 or so, and recovery means dropping to another gear.

 

If you do not have a good Stacked Plate aux trans cooler, you have to do this to keep those trans temps in line. Search this on the forum, there is plenty of info out there.

 

You asked where the revs were at 70MPH. Although some people will tow a camper at this speed, my advice is; don't do it. I tow in 3rd gear and stay at 55 or less on 2 lane roads and around 60 to a max of 65 on the interstate. At 55 in 3rd I am running about 2400 RPMs if I remember correctly. This sounds high to some but the little 5.3 loves this RPM and will do it all day and night and never complain. I hardly ever drive this truck when not towing so I cannot remeber where the revs are at 70 MPH in 4th gear. ( I could call my Wife and asked her but she would only say "what is an RPM". I think around 1900 but I just cannot remember for sure.

 

One last thing. If you are concerned about MPG and the 4.10s, consider this. If you do a lot of Intestate speeds driving, the 4.10s will hurt you some. If you spend the majority of your time on rural 2 lane roads, the 4.10s may actually help you. I am averaging above 18 MPG in my Yuk XL right now, when not towing of course.

 

 

Let us know what you do.

[ken1mod]

Gentlemen,

 

I have a 5.3 with 3.73 gears. I tow a boat a few times a year and enjoy between 18 and 19 mpg in hilly country (without the trailer) It is a good compromise. My truck squeaks the tires when the trans hits second and have good results towing. Remember, while it is fun, you do not have to go 80 up a 7% grade. We have one here and I do 70 with half throttle and pass nearly everyone.

 

18 wheeler pilots call it "soft pedaling" and it is a good concept.

 

If you tow most of the time, I would get the 4.10s. If it is a few times a year, get the 3.73s. I like mine and would get them again.

 

Ken

[C & A s Dad]

Ken, I am certainly not "beating up" on 3.73 gears but I do have to say one thing. Towing a boat, even if it weighs the same as a camper, is not the same as towing a camper. I am guessing your boat is 4,000 to 5,000 lbs ??? His camper is a 6,500lb wind dragging brick.

 

Again, nothing wrong with 3.73s but with the info he has provided, I would have to stick with the 4.10 recommendation.

[saltwater_addict]

3.73 will work, 4.10 will work better. ive towed plenty with my 3.73's sometimes ive wanted 4.10s 3.42's suck

[chakis24]

what would the cost be to swap gears? i have the basically the same setup as him (dont know if having the g80 and autotrac makes things more difficult or not), 3.42 w/ 285/70/17 tires. front and rear would need to be done since its a 4x4 as well. 4.10s would be nice, maybe a little higher (or is it lower?) since eventually id like 34 or 35 inch tires and i eventually plan on towing.

[pm26]

what would the cost be to swap gears? i have the basically the same setup as him (dont know if having the g80 and autotrac makes things more difficult or not), 3.42 w/ 285/70/17 tires. front and rear would need to be done since its a 4x4 as well. 4.10s would be nice, maybe a little higher (or is it lower?) since eventually id like 34 or 35 inch tires and i eventually plan on towing.

 

By using oversize tires, you are making the things only worse. You essentially have 3.35 gears or something like that with those tires. Not good for serious towing. If you attempt to mount 35 inch tires on that vehicle, at least 4.56 gears are a must, maybe even 5.13s, if you want to tow anything bigger than a jet ski with it.

 

And to illustrate my point, vehicles that use huge tires must compensate with gearing. The old Army M123 tractor truck uses 14.00/24 tires, which are huge and stand over 50 inches tall. The gear reduction is 10:1 on all three axles!!!!!!!

 

http://www.blimdanet.com/antiguos/manual64/t02.jpg