Axle changed from 3.73 to 3.42

tealboy · July 18, 2006

I noticed on the 2005 tahoe and suburban, the axle ratio was changed from the std 3.73 to a 3.42. I suspect this relates to GM's desire to improve fuel economy, particularly on the highway. However, i noticed on the new 2007 models, they went back to the 3.73 as std.

anyone know what's going on with the axles? Personally, i like the idea of the 3.42 since i never tow more than 3,000 pounds, plus some cargo, so that falls well within the specs. The 3.42 will provide better mpg and lower engine rpms, which helps minimize engine noise too.

any reaction to the 3.42? I am inclined to find a 2005 used model, as opposed to a 2004 when they used the 3.73.

also, when i read consumer reports, one of the areas rated negatively is the suspension. what is the problem with the suspension on these vehicles?

Ape0r · July 18, 2006

Meh, I have 3.73, wish it was 4.10. Drove a 4.10, thing was a beast going up hills, didn't need to downshift the way my truck would've. Couldn't imagine going to 3.42 from this! I get 19 mpg pretty much all the time. Don't do much 'city' driving, just cruise past a few stoplights on my way to the open road to work.

The problem with the suspension is that the guys at consumer reports are a bunch of bitches and want a carlike ride in everything.

AG Bill 05 Z71 · July 18, 2006

Like most things in life, there are trade-offs in decisions like selecting axle ratios. Why stop at 3.42s if a smaller number ratio is better for gas mileage and gas mileage is real important to you? How about 3.08 or 2.83s? They should be even better, right?

The reason is the axle ratio affects other driveability issues with your truck. With 3.42s your truck will have a tendency to downshift out of overdrive to 3 when going up small hills or even larger freeway overpasses. When you tow anything, you will have to stay in 3 (not OD) because it will be constantly downshifing. Your acceleration or quickness off the line will be slower and you will have to give it more gas to move out quickly. You, however, will get slightly better mileage, all things being equal.

My trade-off is the fact that I hate it when I am in cruise control and the transmission is constantly downshifting out of overdrive and the engine reving up and down. I am willing to trade-off a little less mileage for what I think is better driving characteristics, so I have 4.10s. I would be very unhappy with 3.42s no matter what small additional mileage they provided.

So.....the bottom line.....there is no "correct" axle ratio, just personal preference. I would recommend you drive some of your friends trucks with different ratios to see what works for you before you make a final decision.

tealboy · July 18, 2006

Good points bill, thx. I can relate to the constant shifting b/c my exped w/ a 3.73 and a weakling engine shifts constantly when approaching small hills or overpasses. being in florida, hills are an issue, but the overpasses are. I hate the shifting. I thought my last expedit with the 3.31 axle was the problem, but when i got the larger 5.4 liter engine and the 3.73, the symtom was the same. I'm sure a little better, but very disappointing that it did the same thing. Therefore, since i am entirely against the 4.10axle personally, the 3.42 will probably work for me, but i suppose the 3.73 would be ok too. I still find it interesting that with all the gas mileage pressure, gm went back to the 3.73. That tells me something right there.

OFF-RD · July 18, 2006

Well my new truck has the 3.42s, and I am so happy it does. In fact, if I had seen 4.10 ratio listed on the window sticker I probably would have stayed away from this truck. With gas at $3.00/gallon here now, every mpg counts. And this truck with 3.42s is getting better mileage than any fullsize truck I've ever owned in my life including Dodges, Fords, and one other GM. I have been averaging 17 mpg overall. It's amazing.

Now, like the other guy said, when I hook on my trailer and tow my Jeep YJ (6,000 lbs. total) my mileage drops to 10 mpg. Maybe...just maybe my mileage would be 11 or 12 mpg if I had 4.10s, but who cares? 95% of the time I'm not pulling a trailer so THAT is what matters to me. How can I get the best mileage in my TYPICAL driving conditions? That's the question you ought to ask yourself. For me, I do work with my truck but MOST of the time it's a vehicle to get me to my job and back. So the 3.42s are perfect. Any taller gear and the truck would struggle, any shorter gear and the truck would turn too many RPMs. 3.42 is the perfect happy median.

Oh, and as far as why CR rated the suspension poorly.... go drive a new Dodge 1500 for a week and then get back in your Chevy and you'll see exactly why they rated the suspension on these trucks poorly. My truck was in the shop twice in the first 300 miles because the suspension sucks so bad I honestly thought something was wrong with it. Having come from Ford and Dodge trucks I just didn't know any better. It's "normal" for GM trucks to ride like this. I'm getting used to it now.

Good luck.

asilverblazer · July 18, 2006

Whats wrong with the suspension?

Consumer Reports, that's what. Why would you trust a company that built itself rating toasters and vacuum cleaners to rate a vehicle? Maybe you should listen to Car and Driver...

OFF-RD · July 18, 2006

I agree that Consumer Reports has no business rating vehicles. They are total morons. They have no clue what on Earth they are talking about most of the time.

I will also agree that the suspension on these new GM trucks is AWFUL. When you are cruising on a smooth highway at 55, and you look over and your passenger seat is shaking violently, there is a problem somewhere. When you test drive another new truck just like it off the dealer lot and it's even worse, there is a problem. When your friend who has a GM truck has the same problem, and many people are visiting the forums online with complaints about the ride quality...NEWSFLASH...there is a problem. The suspension on these trucks sucks. Period.

Now, what I can't figure out is...are the springs/shocks too soft, or are they too stiff? Which is it? It's honestly hard to figure out. The springs on these trucks look like something you'd see on a 3/4 ton. But...when you hit a dip in the road the truck sinks like a Cadillac. And I notice they don't use Bilsteins anymore...some cheap Teneco crap or something like that. So maybe the shocks are the problem? It's really hard to decide what exactly needs to be done to make this truck ride like it's supposed to. Do we need to stiffen them up, or make them softer?

drumset5994 · January 23, 2007

When i drive my truck, i like it rough. Piss blood out of your kidney's rough.

Woah, holy old post revivial. Sorry.

NCCamper2003 · April 9, 2007

I know I am bringing up an old topic, but I have a question. I just got a new to me '05 Seirra 1500 SLT, with the 5.3 engine. A few questions:

1. How can I tell what rear end I have in it?

2. Where is the sticker that shows the option codes located?

3. Where can I find a resource to help interpret that sticker? You know, like if my Bonneville has the LN7 engine, then I can see that it's a 3800 NA engine, for example.

Love the truck! Looking forward to several years of great ownership!

NCC

NCCamper2003 · April 9, 2007

Ok...

It looks like the RPO code sticker is on the glove box door. The code for the rear axle looks like it's GU5, making it a 3.23 rear end, if I read the codes correctly. Now with a 5.3L and 3.23 rear end, how well do you think this will do pulling a 5000# max maybe a little lighter hybrid travel trailer? Thanks for any replies!

NCC

cerbomark · April 9, 2007

I know from experience. I had an 07 4.8 with 3;42 (silverado) drove ot 5000 miles and traded it in for all the above stated reasons. Got a 6.0, with 4.10 s < Same truck except for that. Get the same mileage if not 1 more with the 6.0.... Could not stand the constatnt shifting, and some times dropped two gears on hills or passing. Never will I make that mistake again...

Frank Sub · April 9, 2007

In our quest for cost savings we target fuel economy because we see those $$'s floating out of our wallet each week, when we fill up. The big cost of owning any newer vehicle is depreation (on a new truck as much as $9 per day), which far outweighs the cost differential between $1 and $3 gas. Keep in mind that the reason we have trucks instead of cars is we want a vehicle that will do more than get us from point A to point B. We want our ride to also haul, or tow our stuff. Don't go too low on your axle ratio--you will be disappointed. Me--I have a 2001 Suburban with a 5.3 and 4.10, and love it. Tows my 7500# Airstream with ease, and there is plenty of room for my stuff inside, or on top, and get 16.6 mpg with only stuff. My first car, a 1940 DeSoto, got 13 mpg, city, highway, or parked. We've come a long way.--Frank Sub

C & A s Dad · April 9, 2007

Frank, I am right there with you. My '02 Yukon XL is also a 4.10 geared truck and I almost did not buy it for that reason. I thought I wanted 3.73s. However, each time I hook up my 6500 lb camper I am so happy I stuck with the 4.10s.

NCCamper, I hate to be the bearer of bad news but your truck is perfectly capable of towing a 5,000 lb camper if you remove the "passenger car" gears. I would tell you that 3.73 s would likely be ok but a set of 4.10s would get the 5.3 in it's "sweet spot" and have no problem towing 5,000 lbs.

As far as the MPG with 4.10s. I have to stick to what I have been saying. It all depends on your driving conditions. If you spend a great deal of time on the Interstate at speeds upwards of 75 then the 4.10s may not be the gear for you. If you use your truck like I do and it gets driven on mostly rural roads at speeds less than 65, the 4.10s are great. My avg MPG with my Yukon XL with 4.10s s running over 18.5 right now. If I drive it on nothing but the highway it will get over 21. These calculations are based on acutal miles driven divided by gallons used, not by the DIC. It gets between 11 and 12 when towing my camper.

One last thing, I am assuming GM went back to the 3.73s in the '07 SUVs because of the new 6 spd transmission which gets the final drive ratio way up there.. I am not sure if all new SUVS have the new 6 spd ????