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Topic: Silverado 3.08 vs 3.42

Posted By: cVIZgo on 12/17/11 08:44am

In the 2011 1500 Silverado with the 5.3 they offer a 3.08 and a 3.42. Keeping that is mind with two trucks that are set up exactly the same (suspension package, towing package, cooling package) why is it that the 3.08's max towing capacity is 7,000 pounds and the 3.42 is 9,700?


Keep on Truckin'



Posted By: donn0128 on 12/17/11 08:55am

It all boils down to torque available at the rear wheels.
BTW IMHO neither of those axle ratios is worth a hoot for towing at their rated loads. Especially so when you load the grocery getter up with family and stuff.


Don,Lorri,Max (The Rescue Flat Coat Retriever?)
The Other Dallas



Posted By: blt2ski on 12/17/11 09:05am

Actually, with the new 6 sp auto trannys, a 3.08 geared rig has an overall lower initial take off gear than the old 3&4 sp autos with 4.10 gears. Not sure that there is an issue with the taller gears as there has been in the past.

Marty


92 Navistar dump truck, 7.3L 7 sp, 4.33 gears with a Detroit no spin
00 Chev C2500, V5700, 4L80E, 4.10, base truck, no options!
92 Red-e-haul 12K equipment trailer

Check RV.Net Blogs at: blog.rv.net


Posted By: music69 on 12/17/11 09:21am

It's a fair question, but nobody here can answer it. The steeper gearing ratios in the 6L80 6-spd auto helps a lot, but there's still a lot of engineering factors. That's a 10% difference in gearing, but a ~17% difference in combined weight rating. Where you're really going to notice is at highway speeds, not pulling out. I'd guess the 3.08 would be shifting from 4th to 3rd a lot more with 7000 lbs in tow than the 3.42 (which would hold 4th through moderate terrain).


Posted By: TomG2 on 12/17/11 09:23am

With the six speeds, it is possible that there is actually a better cruising gear with the 3.08 than the 3.42. Fourth with the 3.08 might put you in a better rpm range than fifth and the 3.42. Like blt2skis said, the 6-speed transmissions change some things. Don't bother pointing out sixth gear would provide less torque to the rear wheels with the 3.08, as few tow in sixth gear with a small block anyway. Yes, I know that every diesel does. (According to the folks on here).


Posted By: MSGMadhatter on 12/17/11 10:14am

I have now a 1500HD CC Silverado, 6L, 373. I had a 350 (5.7), 342 before this. A 373 will do you a better job. no comparison. I tow a 34' TT about 8000 lbs.

Some times I wish I had a 8L 454 like the one in my CLass C.


MSG MADHATTER (Life Member Good Sam)
1500 HD Silverado, 6L
Jayco Eagle Super Light 298RLDS (Hers)
Jayco Greyhawk 24SS Class C (His)


Posted By: TomG2 on 12/17/11 10:48am

MSGMadhatter wrote:


Some times I wish I had a 8L 454 like the one in my CLass C.


I don't think they offer the 454 in the 1500 series, and I wouldn't want one if they did. BTDT. I think the OP is looking at a 5.3 liter engine.


Posted By: jamtz on 12/17/11 12:30pm

I read all the hype all the time about how bad the 3.42 axle is with the 5.3 in the Silverado but I own one and pull a 7000lb TT loaded with it. It pulls just fine on flats and mountain terrain. Its no 2500 or 3500 this is true. I'm comfortable with it pulling and as a daily driver. Don't expect racing speeds or 80 mph down the road. It all boils down to what you are comfortable with. As far as the 3.08 axle, I couldn't tell you. Just do what makes you happy. How heavy are you going tow with the 3.08?


2011 Chevrolet Silverado 1500 LT Z71 EXT CAB 5.3L V8 3.42 axle 4x4 (Old TV)
2015 Chevrolet Silverado 2500HD LT 6.0L V8 4.10 axle CC 4X4 (New TV)
2010 Coachmen Catalina 28BHS
EAZ-Lift WD Hitch w/sway control



Posted By: cVIZgo on 12/17/11 01:02pm

The trailers I'm looking at are all between 7500 and 8500 pounds. My concern is why the 2700 pound difference betweent he two gears. Is it a mechanical difference? Maybe the teeth on the ring and pinion are smaller maybe the pinion shaft is smaller diameter making it weaker? I'm just having trouble wrapping my head around a 2700 pound difference when everything on the truck is the same but the gear.


Posted By: blt2ski on 12/17/11 01:36pm

As mentioned, the torque multiplication of the axel ratio. Other than that, frankly, both will tow about the same overall. The 3.42 will have maybe a bit quicker take off, better initial grade take off......other than that, a given chassis will handle the given trailer the same. At the track, one should be better per say than the other.

If you have a 3.08 geared rig, want a rig that is 500-1000 lbs more wt than rated, I would not go out and buy or change out the gear sets to 3.42's because of the GCWR ratings. My old 96 K3500 SW 6.5TD has more initial gradiablity than my dmax, because the 4.10 axel gears, and 5.86-1 first gear multipply the torque of the motor such that the 96 with a 12K gcwr will pull approx 10K lbs up a 30% grade before stalling, yet the dmax is all of 24% at 20K. Now due to the HP of the dmax at 320 vs 185 f the 6.5, well, freeway grades I go 60+ with the dmax in direct, about 35- 40 in the gear below direct with the 6.5.

Like all things great and small. it is really up to you. Performance is a rather personal issue frankly.

For me, I like a chassis with a GRAWR of at least half the capacity of the trailer to be towed, so in your case, about 4000+ lbs, Payload for the occupants, weight etc. Enough HP to go at least 50 on a 5-6% grade, 30+% gradability at the GCW I will be at. Frankly, my dmax fails the gradability part!

Marty


Posted By: jamtz on 12/17/11 01:40pm

Not too sure how to answer that except that maybe its the difference in torque from the 3.08 to the 3.42 axle.


Posted By: cVIZgo on 12/17/11 01:52pm

Torque to get load moving? Cause again, same engine and trans? If it's only to get load moving, why the huge weight difference?


Posted By: donn0128 on 12/17/11 01:57pm

It may be the same engine and transmission but the rear end ratio is a multiplier to put the power to the ground. If you had for example a 1:1 rear end ratio you might be able to go 200MPH, but you would NEVER get the rig rolling without a push car. Conversely if you have a 6:30 rear end in the exact same rig, you could pull a freight train, but probably could never go over 50MPH.


Posted By: lbrjet on 12/17/11 02:13pm

You will have more HP at any given speed.

GM is trying to tell you the 3.08 gears are their worst gear set for towing. Even if you don't understand why, you should listen to them.


2010 F250 4X4 5.4L 3.73 LS
2011 Flagstaff 831FKBSS
Equalizer E4 1200/12000


Posted By: MARK VANDERBENT on 12/17/11 02:39pm

I am hearing a lot of good things about the new 6 speed trans. 308 and 342 rear ends feel a lot better towing, and fuel mileage is up. I would get the 342. I have a 97 burb 1500 350 with a 342, and it tows great in 3rd gear.


Posted By: GuyM on 12/17/11 02:52pm

I have a new GMC Ext. Cab, 5.3 with a 3.08. With the 6 speed it handles my 4800 lb. trailer (scaled weight) just fine. In fact I get up to speed quicker than I did with my 5.7, 4 speed with a 3.73. The only time I feel that I'd like more gear is when I try to run at 65+ mph. Most of the roads I drive are 55 mph limit, so the 3.08 works just fine for me when I'm towing. Towing only makes up less than 20% of my miles, so I'm very happy with the 3.08.


Guy


Posted By: cVIZgo on 12/17/11 03:01pm

I've pulled my rig estimated 4500 pounds with out a problem at all. But my fiance and I have been in the market for new TT and the area we've been looking keeps taking us around the 8,000 pound range loaded. Less the the 3.42 towing capacity but over the 3.08 capacity and I'm trying a reason why there is such a difference between the gears. Is there a way to ask Chevy or a technical forum where I may get a chevy tech who may have the answer to this?


Posted By: APT on 12/17/11 04:54pm

7000-8500 pound RV is really pushing half ton suspension, regardless of motor, trans, and gearing. A boat, sure, but most people are not comfortable towing RVs that much with them. Are those dry weights or GVWR? 8000 pound RV means 1000-1200 pounds of tonque weight. Most half ton trucks only have 1500 pounds of payload, leaving 300-500 pounds for family and cargo in the bed.

If you insist on the 5.3L, get the 3.42 for more torque. There is no penalty, only 11% more wheel torque. But I'd look at under 6000 pounds dry or 3/4 ton truck.


A & A parents of DD 2005, DS1 2007, DS2 2009
2011 Suburban 2500 6.0L 3.73 pulling 2011 Heartland North Trail 28BRS
2012 VW Passat TDI


Posted By: dodge guy on 12/17/11 04:59pm

It`s more than just getting the load moving. it`s also about keeping the load moving and how easy it will be. there is nothing different about the strength of the gearsets, more the mechanical advantage. just like when you change gears on a bike. the lower the gear (higher number) the easier it is to move a given load. the higher the gear (lower number) the more work it takes to move it and keep it moving when loaded.


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Son Brandon 13yrs
Daughter Marissa 12yrs
Dog Bailey

07 Cherokee 32B
02 Excursion 4X4 V-10 4.30 gear 5Star tuner Y-pipe mod Hellwig sway bar
Reese DualCam, Prodigy brake controller

A bad day of camping is
better than a good day at work!



Posted By: maxwell11 on 12/17/11 06:19pm

i had a GMC with a 3.42 differential ratio.

great truck to drive back and forth to work and for light work.

but, when i hooked mama bears camper to it, you would have thought i had hooked the pickup to a big tree.

I would not want anything less than a 3.73 and that depends on the motor and trailer weight.


Remember: you need at least 20% overage in tow capacity and sometimes that is not enough. Also, remember when some fool pulls out in front of you and you have to shut her down quick, your truck/trailer cannot have enough brake capacity.
bigger tow vehicle is better:

jmtc
good luck and stay safe,


Posted By: JIMNLIN on 12/17/11 08:20pm

As others have been saying there is no need for the old 3.73/4.10 gear ratios with the new 6L80E trannies/5.3 engine. The 6L80E 4th and 5th gear splits are just above and just below 1:1 3rd gear in the old 4L60E trannies.

The 3.42 gears have more rpm available at a given speed. More rpm = more power multification than the 3.08 gears at the same speed. More power = higher tow ratings.


"good judgment comes from experience, and a lot of that comes from bad judgment" ............ Will Rogers

'03 2500 QC Dodge/Cummins HO 3.73 6 speed manual Jacobs Westach
'97 Park Avanue 28' 5er 11200 two slides


Posted By: Nick R on 12/17/11 08:23pm

the 3.42 will also come with the k5l heavy duty tow package which gives you an engine oil cooler and an auxillary trans cooler. This heavy duty tow package is not available with the 3.08's.


Posted By: cVIZgo on 12/17/11 08:28pm

Nick R I have all of the HD stuff. Towing package, towing suspension, trans and oil coolers, and the 3.08 gear.


Posted By: TomG2 on 12/17/11 09:40pm

What is also interesting about the ratings is that there is no difference in the estimated highway mileage for both ratios, 21 mpg Highway.


Posted By: jamtz on 12/17/11 11:15pm

This rig includes a 2011 chevy silverado 1500 ext cab w/5.3L and 3.42. It tows the trailer loaded without problems and well within weight ratings.

The trailer has an unloaded weight of 5469lbs and dry hitch weight of 775lbs. I run the trailer about 6500lbs loaded. With a gvwr of 7000lbs and a crub weight of 5368lbs, 4 people in the cab, nothing in the bed, and the trailer hooked up, I am well within my 80% of payload capacity and gcwr. It tows great with no problems and properly equipped with brake controller, operational trailer brakes, wd/sway control, and a responsible operator at the controls, theres nothing unsafe about it.




Posted By: SoCalDesertRider on 12/18/11 06:28am

The reason is very simple: increased torque multiplication and increased engine rpm for the 3.42 versus the 3.08 axle ratio, at any given road speed, in any given transmission gear. It's simple math applied to the properties of a simple machine. Gears are one of the simple machines you learned about in high school physics, along with lever & fulcrum and pulley block.

Work = Force x Distance.

Increase the Force, the amount of Work that can be done also increases. An example of increasing the Force would be using a bigger engine with higher power output.

Increase the Distance over which the Force is applied, the amount of work that can be done with the available Force also increases. In a gear set, increasing the Distance is accomplished by increasing the size of driven gear, or decreasing the size of the drive gear. The more times the drive gear has to spin to turn the driven gear one time, the greater the distance the engine's power is applied and thus the greater amount of Work that can be performed.

In an axle ratio, the ratio is expressed as X:1, where X is the size of the driven gear (ring rear) in relation to the drive gear (pinion gear). The drive gear's size is expressed as a constant, which is the number 1. So with a 3.08 ratio, the driven gear is 3.08 times larger than the drive gear. With a 3.42 ratio, the driven gear is 3.42 times bigger than the drive gear.

What this means is if your engine has say 400 lb-ft of torque available at some given rpm, the axle gears will multiply that torque by a factor equal to their ratio.

400 x 3.08 = 1232 lb-ft of torque at the axle shafts
400 x 3.42 = 1368 lb-ft of torque at the axle shafts, at the same engine rpm as above.
This is a difference of 136 lb-ft of torque at the axle, with the same engine output.

A gear set is nothing more than a lever and fulcrum where the lever ends are round instead of straight. The longer the end of the lever arm that you apply the force to, the greater the torque multiplication and the more weight you can lift with the same downward force applied to your end of the lever. The smaller the drive gear in relation to the driven gear, the more torque you have available to move the load.

There is also the rpm increasing factor of using a lower ratio gear set (3.42 is a lower ratio than 3.08). As engine rpm increases through the useful power range of the engine, horsepower and torque output also increase. Since the lower 3.42 ratio causes the engine to spin more rpm's at any given road speed than the 3.08 ratio, not only is torque multiplication greater with the 3.42 ratio, there is also more torque available to multiply.

So the real life scenario looks more like-

400 x 3.08 = 1232 lb-ft of torque at the axle shafts
425 x 3.42 = 1445 lb-ft of torque at the axle shafts, at the same road speed and in the same transmission gear
This is a difference of 213 lb-ft of torque at the axle

As torque and rpm increase, so does horsepower.

The formula to find horsepower from known torque and rpm is-

HP = Torque x RPM / 5252

At 600 revolutions of the tire per minute per mile (60 mph), with 1232 lb-ft of torque at the axle (3.08 axle ratio, 1.00 trans ratio), there is 141 horsepower available at the rear wheels.

At 600 revolutions of the tire per minute per mile (60 mph), with 1445 lb-ft of torque at the axle (3.42 axle ratio, 1.00 trans ratio), there is 165 horsepower available at the rear wheels.

This is an increase of 24 horsepower at the rear wheels, compared to the 3.08 axle ratio. 24 / 141 = .17, which means a 17% increase in rear wheel horsepower with the 3.42 axle ratio, versus the 3.08 axle ratio.


05E350 6.0PSD
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69Bronco ATC250R CR500
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4.56's & LockRite rear


Posted By: SoCalDesertRider on 12/18/11 06:37am

JIMNLIN wrote:

The 3.42 gears have more rpm available at a given speed. More rpm = more power multification than the 3.08 gears at the same speed. More power = higher tow ratings.
JIMNLIN summed it up very well in one sentence in his statement above.


Posted By: SoCalDesertRider on 12/18/11 06:40am

cVIZgo wrote:

Torque to get load moving? Cause again, same engine and trans? If it's only to get load moving, why the huge weight difference?
Not only the increase in torque to get the load moving but also the increase in rear wheel horsepower to keep the load moving, as well as climb grades, pass slower traffic and merge onto a roadway. More power at the rear wheels = greater ability to tow more weight, or move a higher profile load through the air.


Posted By: SoCalDesertRider on 12/18/11 06:42am

donn0128 wrote:

It may be the same engine and transmission but the rear end ratio is a multiplier to put the power to the ground. If you had for example a 1:1 rear end ratio you might be able to go 200MPH, but you would NEVER get the rig rolling without a push car. Conversely if you have a 6:30 rear end in the exact same rig, you could pull a freight train, but probably could never go over 50MPH.
Donn0128 did a good job describing the role of axle gearing, with his explanation and analogy above.


Posted By: SoCalDesertRider on 12/18/11 06:45am

dodge guy wrote:

It`s more than just getting the load moving. it`s also about keeping the load moving and how easy it will be. there is nothing different about the strength of the gearsets, more the mechanical advantage. just like when you change gears on a bike. the lower the gear (higher number) the easier it is to move a given load. the higher the gear (lower number) the more work it takes to move it and keep it moving when loaded.
Dodge Guy also did a good job with his explanation above.


Posted By: TomG2 on 12/18/11 07:09am

Great explanations all, but things were much more critical back in the day when we drove three speed standard shift vehicles. We Hot Rodders were the first to install a 4.11 or even 4.56 ring and pinion to get things moving faster. Now we can drop down a gear in our six speeds to match road conditions without changing the differential. Yes, in sixth gear, there are more rpm's available but we don't "have" to run in sixth all the time.


Posted By: JIMNLIN on 12/19/11 08:00am

Uhhh, TP's "Too many freaks & not enough circuses ~ " is in his profile and wasn't a shot at ya'. IMO you need a break.


Posted By: dodge guy on 12/18/11 05:41pm

TomG2 wrote:

Great explanations all, but things were much more critical back in the day when we drove three speed standard shift vehicles. We Hot Rodders were the first to install a 4.11 or even 4.56 ring and pinion to get things moving faster. Now we can drop down a gear in our six speeds to match road conditions without changing the differential. Yes, in sixth gear, there are more rpm's available but we don't "have" to run in sixth all the time.


Still not getting it! yes you can drop a gear with a 6 speed, but now you have a 5 speed with less motivation. reread what we are all saying it`s all about physics.


Posted By: TomG2 on 12/18/11 07:14pm

As an engineer myself, I "Get it". Just take a look at what real trucks are doing these days. Higher gear ratios, almost idling down the highway, thanks to improved computers and engineering. Nothing is as simple as "Put in a lower gear" anymore. Get it? I am "Not" suggesting that a lower gear ratio (higher numerically) is going to have less horsepower available at "x" mph, just that things are not as simple as some would suggest.


Posted By: SoCalDesertRider on 12/18/11 10:59pm

TomG2 wrote:

As an engineer myself, I "Get it". Just take a look at what real trucks are doing these days. Higher gear ratios, almost idling down the highway, thanks to improved computers and engineering. Nothing is as simple as "Put in a lower gear" anymore. Get it? I am "Not" suggesting that a lower gear ratio (higher numerically) is going to have less horsepower available at "x" mph, just that things are not as simple as some would suggest.
The newer engines are producing more power now days than they used to. 400 hp and 800 lb/ft from the latest generation diesels in today's pickups, compared to 300 hp and 600 lb-ft just a very few short years ago and 200 hp and 400 lb-ft only a bit more than a decade ago. When you increase the engine power output, you can decrease the torque multiplication by the axle ratio and get the same power to the wheels.

800 lb-ft x 3.31 = 2648 lb-ft at the wheels
400 lb-ft x 6.62 = 2648 lb-ft at the wheels

Electronics or no electronics, if today's diesel pickup engines were still producing the same 400 lb-ft torque output as they were 10-15 years ago, the same 6.62 axle ratio would still be needed to yield 2648 lb-ft at the rear wheels and the resulting towing power performance.

The math does not change when computers and electronics are added, it is still all the same, if the power output of the engine remains the same. The electronic control may make the same output engine more efficient and use a little less fuel to make that power, but power output and gearing are still in equal relationship and governed by the same physical principles, as always.


Posted By: Turtle n Peeps on 12/18/11 11:48pm

Well said SoCal.


~ Too many freaks & not enough circuses ~


"Life is not tried ~ it is merely survived ~ if you're standing
outside the fire"



Posted By: TomG2 on 12/18/11 11:58pm

That is the way to make a point. Calling someone a "Freak", just because they have a different opinion is about as stupid as anything I have seen on here. But, consider the source!


Posted By: TomG2 on 12/19/11 05:26am

The OP will not be towing in sixth gear. Get it? Tell me why it is such a terrible thing if he is going happily down the road in fourth gear at sixty mph with 2,700 rpm's or fifth gear at sixty mph with 2,700 rpm's. I did not say fourth gear was "better", just not terrible. Yes, I would prefer the lower rear axle ratio in most cases and it would be better to have five speeds for acceleration than four.


Posted By: cVIZgo on 12/19/11 06:12pm

WOW, I can't say enough about all the responses from everyone. Thank you so much. I'd like to give an update and also post a few things, I'm interested in all of your thoughts.

1. I called my dealer today, $2,043.72 to have the gear changed from a 3.08 to a 3.42. He had no explanation why the truck is set up with every HD towing thing available except for the gear being the small one.

2. I have "a guy" who may be able to take care of the rear end put in the 3.42 for much much less but I'm afraid that it will void the warranty and I'm not sure I'm willing to run that chance.

Another angle:
What if the gear stayed the same and I went the power adder route? Cool air intake, exhaust, maybe add 30-40 horsepower? Does this make a slight difference in the outlook of the OP?

Final thoughts...
There have to be other 3.08's out there that have no idea. Maybe bought a truck cause the wife said lets camp and are pulling a 9,000 pound camper cause they believed thats what they can tow. When in reality they have a 3.08 and are way way way out of their "towing limits." I'm glad I looked into this, I have people to chat with and help me understand the situation. I'm bet these 3.08's that are out there towing 9,000 pounds just blame it on an underpowered truck and keep on moving instead of the fact its not underpowered its under geared.

LAST THING I PROMISE... Keystone 3050 and 3020 are the campers that provoked this conversation, there are many more options I know, but my fiance' and I have fallen in love with both these rigs.


Posted By: SoCalDesertRider on 12/19/11 07:04pm

If your truck is 4wd, then $2K is in the ball park for cost of changing both front and rear axle gear sets. If your truck is 2wd, then $2K is major robbery.

Take the truck to a local axle and driveline shop, or hot rod shop, or off road shop. These places do gear changes all the time and they are experienced at setting up the gears right. I would never take a truck to the Ford/GM/Dodge/etc dealer for a gear change. The dealerships are overpriced and lack experience with axle gears.

No need to worry about voiding the manufacturer warranty on the axle gears, provided the shop you use provides their own warranty on their work.


Posted By: APT on 12/20/11 06:25am

I would buy one of the two Passports you like and drive it for a season or two. The 6-spd/3.08 is similar, but slightly better than the old 4-spd with 4.10 axle. First gear is very close, and you'll probably be able to use 4 gears vs. 3 of yesteryear. Few people complained about the old 4-spd with 4.10 axle towing 7000 pounds.

If you feel you need more acceleration only, then $2k towards 3.73 or 4.10 gear would be great. But you may find yourself wanting more suspension as well and a 3/4 ton gasser would be a great upgrade in a couple years.


Posted By: MSGMadhatter on 12/21/11 12:02pm

Considering a new tow vehicle. IF YOU are really concerned if the truck will do the job, it is better to have more than not enough.

I replaced a Suburban, 5.7 342 with a 2003 1500HD CC Chevy 6L, 373.
1500HD is vastly better than my SUB. Suspension, also has a lot of effect on towing. My next TV will be a 2500HD.

Drive a 2500HD Silverado, and you will be sure and know it will do the job if you cannnot afford a Duramax diesel.

RV owners usually by a small one first then want a bigger heavier one
and dont have enough truck to pull it.


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