I am looking at buying a new truck . I have a 05 5.9 auto with 3.73/1 ratio
I want a manual trans on my new truck and I'm looking at 07-09 models at this point. Almost everyday I pull a trailer that can way as much as 25k but on average is 12-15k and drive some on flat and some in the hills(steep). I want a gear that gives me the best overall fuel milage.
I read somewhere that they changed the 6th gear ratio in the g56 manual trans around 07 but not sure when, so that throws another kink in the thought process.
I don't like my 48re because it wont hold a gear in the hills and have all the mods and it still needs a freshin up often. So I want a manual.
I figured, just to try and get a 6spd manual with 3.42 gears to get as close to 1900rpm at 70 as possible. But a buddy told me that it will get better milage if you go taller gears and drive in 5th loaded. Then another told me to go lower gears like 3.73 or the 4.10 and my maintenance and fuel cost overall would be lower from less stress on truck..
I would like to know would y'all think.. please specify if your reply is opinion or fact based please... As always thanks in advance

 

Just to add another opinion here to your options, but I think you should look hard at the 68rfe as this trans is awesome. Exhaust brake and 6 speeds. I have heard of nary an issue anyone has with these. Stock to stock the 48re does not hold a candle to it.

 

I agree. but the 68rfe's are still not holding up as good as the manuals, Acording to several local shops..
And when they need rebuilt it will cost several thousand. A manual may need a bearing and/or clutch but that is only hundreds as I can make those repairs myself

 

Wow guess I've stumped everyone...lol
Heres another question, If it has the 6.7 does it have the .74 overdrive ratio

 

I am not sure what the final drive ratio is on the manual but I think it's pretty close to the 68RFE. My truck has the 68rfe with 3.73s and at 70 mph I'm running about 17-1800 rpm's.

 

Final over drive on the G56 waaaaay higher rpms than the 68rfe. The 68 has dbl OD and 5th is similar to 6th on the manual. My truck with stock tires was around 2200-2300 rpms at 70mph and that's with the deeper OD gear compared to the 06 G56 models.

To the OP, I'd get the lower gears, 3.73's at least for the weight you pull. Or get 3.42's and if you don't like them I'll swap even money! I don't tow much .

 

I would get the 3.73 gears with the g56 if you tow that heavy... In 6th gear it will pull like a dream. The 3.42 gear set would be awsome for a truck that towed light or was empty all the time.

My old 07 with the g56 had 3.73's and it was perfect for towing.

 

i would go with the 3.73's i have 08 with a stick and 3.42 too tall if i pulled alot with it but for me its perfect