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Choice of rear axle ratio would you pick?

coachrider

By coachrider
in Engines & Drivetrain

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Joe_K Enthusiast

Joe_K

Posted
Posted

"But your mileage is likely not going to be much if any better with 3.08's, so why not get better gears?" I think that's what folks are getting at. My truck, which many would consider "old", has 3.73's and a 4 speed, and still manages over 18 mpg highway. The lower gears aren't going to hurt economy that much.

 

Absolutely, if you can find a truck the way you want with 3.42's, get it. If you are are ordering a truck, I would pick 3.42's. All I'm saying is don't be afraid of the 3.08's if it's all you can find.

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Joe_K Enthusiast

Joe_K

Posted
Posted

In any gear beyond the first gear of the current 6 speed you have no mechanical advantage over any older truck. Like I said before.... Toyota has 430s and a 6 speed much like everyone else but without the granny first gm and ford use and a less harsh gear spread. Just because you have a deep rear gear doesn't mean the truck can't attain reasonable highway economy. That said I also don't buy 5500 lb trucks and want nothing but the best possible economy... I couldn't care any less about mileage to be truthful. But if someone likes the 308s well then let them like them I guess. But when the mileage penalty no doubt will be so insignificant it will not even be measurable.. why bother.

 

Why do I bother...

 

6 speed

1st: 4.02 x 3.08 = 12.38

2nd: 2.36 x 3.08 = 7.27

3rd: 1.53 x 3.08 = 4.71

4th: 1.15 x 3.08 = 3.54

5th: .85 x 3.08 = 2.62

6th: .67 x 3.08 = 2.06

 

4 speed

1st: 3.06 x 3.73 = 11.41

2nd: 1.75 x 3.73 = 6.52

3rd: 1.00 x 3.73 = 3.73

4th: .70 x 3.73 = 2.62

 

5th gear with 3.08's is the same final drive ratio of 2.62 as 4th gear is on the old trucks with 3.73's. There's a mechanical advantage all the way up to that point, with an extra OD gear. I have a hard time seeing your argument that the old 4 speed with 3.73's is better. BTW, Tundra's get horrible gas mileage, and some people do care about gas mileage.

Joe_K Enthusiast

Joe_K

Posted
Posted

I'm at work and bored so...

 

6th gear has a final drive of .67 so:
3.08 gears = 1597 rpm's @ 70 mph
3.42 gears = 1773 rpm's @ 70 mph

a difference of 176 rpm's @ 70 mph

That's probably why I couldn't tell the difference during a test drive.

Badass69 Senior Enthusiast

Badass69

Posted
Posted

My arguement is 410... but look at your own math.... your losing badly other than first gear. So again on the highway where your revs and gears will be useful you have a handicap with 308... this isn't hard. Don't like the 60e like me... use the 80e's ratios. You can talk numbers all you want but even they don't lie. Tundra mileage is about the same as afm oil consumption. .. and I have yet to meet a real world gmt900 owner that brags about stellar economy. Have the 2014s improved... maybe... but then again I still don't care about mileage... if you do.. oh well. Mechanical advantage is just that... and less isn't necessarily a point for fuel economy.

 

Joe_K Enthusiast

Joe_K

Posted
Posted

My arguement is 410... but look at your own math.... your losing badly other than first gear lol. Tundra mileage is about the same as afm oil consumption. .. and I have yet to meet a real world gmt900 owner that brags about stellar economy. Have the 2014s improved... maybe... but then again I still don't care about mileage... if you do.. oh well. Mechanical advantage is just that... and less isn't necessarily a point for fuel economy.

 

Losing badly in all but first gear?

 

1st 12.38>11.41 1st

2nd 7.27>6.52 2nd

3rd 4.71>3.73 3rd

4th 3.54

5th 2.62=2.62 4th

6th 2.06

 

4x4 on the highway A/C on, cruise set to 65, best 25 mile average 25.8. I'm sure I could beat that, but my 4 mile drive to work takes about 25 minutes due to construction.

 

A1253C1E-2CD2-48C1-9F8B-499CAD4C8536-6676-0000056B22CD0DF5_zps7d93825d.jpg

Joe_K Enthusiast

Joe_K

Posted
Posted

Enjoy your 308s... attempt to explain anything here is pointless.

 

I'm willing to listen, but you're not explaining anything with facts, just making baseless comments. Now lets look at your old 4-speed with 4.10 gears which you claim is better than the new 6-speed with 3.08 gears. Ready?

 

6 speed

1st: 4.02 x 3.08 = 12.38

2nd: 2.36 x 3.08 = 7.27

3rd: 1.53 x 3.08 = 4.71

4th: 1.15 x 3.08 = 3.54

5th: .85 x 3.08 = 2.62

6th: .67 x 3.08 = 2.06

 

4 speed

1st: 3.06 x 4.10 = 12.56

2nd: 1.75 x 4.10 = 7.17

3rd: 1.00 x 4.10 = 4.10

4th: .70 x 4.10 = 2.87

 

Look at the final gear ratios in 1st through 4th, the mechanical advantage actually goes to the 6-speed with 3.08's, then you have two overdrive gears. If you're obsessed with having your engine rev higher and drink more gas on the highway, you can put it in manual mode and drop it into 4th, which is essentially what happens when you put the truck in tow/haul mode. Then add in the improved 5.3 and you have a much more capable truck. How is this worse?

blckthree Enthusiast

blckthree

Posted
Posted

I've been reading this with interest, slightly off topic, but just a general question. I've been debating the 3.02 / 3.42 rear end. I have only towed once in my life and it was last week with a Uhaul 12' cargo trailer, two axle, listed at just under 2000lbs. I towed it with my 2009 Avalanche, 4WD, 6 speed and 3.42 rear end. It was one shift happy truck on the rolling hills, and although it never seemed to really labor to pull the trailer along at about 70mph, it did suck a lot of gas. 12mpg with the trailer behind. Is that normal performance for pulling a 2000 lb trailer? I realize I am short some hp and torque compared to the 2014 trucks and the Avalanche is a little over 600 lbs heavier.

 

The Avalanche alone is shift happy without a trailer, which makes me wonder about the 3.08 and whether I would be happy, although looking at the math, only 176 rpms different at 70 mph, how big of a hit could that 176 rpms possible be for fuel economy? Yes, I asked about fuel economy.

 

Mike

Joe_K Enthusiast

Joe_K

Posted
Posted

I've been reading this with interest, slightly off topic, but just a general question. I've been debating the 3.02 / 3.42 rear end. I have only towed once in my life and it was last week with a Uhaul 12' cargo trailer, two axle, listed at just under 2000lbs. I towed it with my 2009 Avalanche, 4WD, 6 speed and 3.42 rear end. It was one shift happy truck on the rolling hills, and although it never seemed to really labor to pull the trailer along at about 70mph, it did suck a lot of gas. 12mpg with the trailer behind. Is that normal performance for pulling a 2000 lb trailer? I realize I am short some hp and torque compared to the 2014 trucks and the Avalanche is a little over 600 lbs heavier.

 

The Avalanche alone is shift happy without a trailer, which makes me wonder about the 3.08 and whether I would be happy, although looking at the math, only 176 rpms different at 70 mph, how big of a hit could that 176 rpms possible be for fuel economy? Yes, I asked about fuel economy.

 

Mike

 

Did you put it in tow/haul mode? You can also put it in 4th with tow/haul mode and it will lock out the two OD gears.

blckthree Enthusiast

blckthree

Posted
Posted

Did you put it in tow/haul mode? You can also put it in 4th with tow/haul mode and it will lock out the two OD gears.

No, I left it in drive. I tried tow/haul mode, but it was holding gears until about 3000rpm, and the trailer wasn't heavy enough to need that, except for hills, where it dropped down to probably 4th gear to get back up them. I didn't notice it was even back there on the flat roads. I figured tow/haul would eat up more gas yet. But at 12mpg, I'm not sure that was possible.

 

I wasn't complaining so much about the performance as the fuel economy. Never having towed anything, I had no idea if that was normal gas mileage or not.

 

Mike

Chris Senior Enthusiast

Chris

Posted
Posted

My guess is the design of the trailer. Kills aerodynamics and a 3.42 will shift. Mine does with my 10,000 pound trailer. Not as much with my 1500 pound horse trailer

Chris Senior Enthusiast

Chris

Posted
Posted

That was one contribution to the poor mileage. I get about 13 with the horse trailer and 8-9 with the travel trailer. But my truck is a 6.0 with a 4 speed and 3.42 gear

MikeNH Senior Enthusiast

MikeNH

Posted
Posted
I laugh at this debate. Do all you that like higher gearing drive around only in first or maybe second gear? Didn't think so... So when you are a little heavy... or even empty and all you have is that 1.5 or 1.15 to one on the highway... 3.08's and 32 inch tall heavy tires. . Well leave lots of room to pass okay. Especially with all that overdrive gear and engines that need to rev... 3.73 minimum. Mechanical advantage is nice in any trans gear..thus putting the mechanical advantage in a fixed position ( the diffs) and not relying on the trans for it makes a better drive.. Toyota is about the only one that actually figured that out.

 

Except the Tundra gets garbage MPG with those 4.30s yet the 6.2 would blow the doors off the Tundra at any towing or other truck task.

BringTheRain403 Senior Enthusiast

BringTheRain403

Posted
Posted
Sigh.... why I bother. Sure you have the same mechanical advantage as a 410 truck in first gear.... whooptee dooo. How about in 4th on the highway... nope you sure don't have the edge on 410... ever. Unless you drive around in first gear all the time you have no advantage.. and really. The 6 speed has what.. granny low and 2 overdrives. Neither are useful for anything for power when rolling. Slow enough speed you get back into second... but otherwise its 3rd and 4th like me with 2nd and 3rd. 308 has no business in a truck... Even 373s in my last 6 speed 09 wasn't anything wonderful. The truck would had been better off 410.

 

Yes you'll have a mechanical advantage in OD gears, if you're not towing anything heavy or never plan on it why do you need the engine revving higher on the highway? Not everybody pulls a 10,000 lb trailer or races a 5500lb truck. If you do, wait for the NHT package or the 6.2. If you use Tow/Haul mode it drags out the gears before shifting. Trust me, this truck has no problem overtaking people on the highway, it's surprisingly quick and it zips right along in town. If you set the cruise to 65mph it gets 24-25 highway mpg.

 

All I was pointing out is I was apprehensive about buying a truck with 3.08 gears due to past experience. I drove several and the only one that had the color and options I wanted with the 5.3 had 3.08 gears. I honestly could not tell the difference between the one I bought and a Dark Maroon one I drove with 3.42's. If I was ordering a truck and had the choice, I would pick 3.42's, but the 3.08's are nothing to be afraid of if this truck is just your daily driver/family wagon. I'm sure the new motor with the very flat torque curve is what helps this truck over the old 5.3.All I can say is that my trailblazer ss has 4.10 gears in it and the 4L60E and it passes everything but a gas station. DIC currently says 10.1 MPG. Cruising on the highway at 70 I'm turning almost 3K. I ordered 3.42's and I would have liked 3.73's. I've had both 3.73 & 3.42's in my camaro and I could honestly tell very little difference between the two. That said 3.08's are gutless gears which would probably make my 80 year old grandmother bitch about it having no balls... Sent from my Galaxy Nexus using Tapatalk 2

 

And someone else with an opinion that probably hasn't driven one.

 

Actually I have. I've driven a truck with both the 3.42's and the 3.08's. I'm cool with 3.42's but 3.08's only deserve to be in your grandparents Buick...

 

Sent from my Galaxy Nexus using Tapatalk 2

 

 

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