Good post Joe

So many think there is a direct connection between RPM and fuel mileage. And so many are willing to run at an unneccesary EGT temp, at low RPM, and just pound the tranny.

Best to let it rev a bit when towing. Use the direct gear for efficiency and less strain. Retain some throttle response. Keep the EGT down.

Just because a Cummins will pull at ridiculously low RPM doesn't mean it's a good idea.

All good points.

 

I tow in 6th, might use 5th on the big hills on the Coq but my trailer weighs a little more than half of yours. I tow with the BDTD set on 'performance' and there's no shortage of power for the hills and I keep a close eye on my egt's.

We'd like to get a bigger trailer, I'm sure I'll use 5th a lot more often then.

 

One other thing about the early G, it does have a notably lower 1st and reverse. The NV I had, I would sometimes need to use low range when manuvering the trailer into a steep, tight spot.

 

5th hear on the highway ? NOT with my 4.10's. I lock the cruise in sixth and roll on loaded or not.

 

Why not drop in 3.42 gears, thats what i did and now its just right on the highway.

 

Changing gears on 2 diffs is too expensive.
My next set of tires will be bigger, we'll see how that works out...

 

Did not realize your truck was a 4x4.

 

I agree that 3.42 axle ratio gears would be better for the early G56 transmission,
Not at all practical to change on 4x4's. Larger diameter tires would be the better choice on 4x4's.

Has anyone researched how the OD ratio change was accomplished on the newer G56?
ie. Can the old G56 trans be retro-fitted to match the new G56 gear ratios?

Since all the ratio's changed in the new G56, perhaps it is a gear that is common with all the gears?
Perhaps something as simple as the input shaft gear?

I realize I'm dreaming out loud for the early G56 guys but for me the NV5600 gear ratio's are very good & the new G56 gear ratios are similar...

...Joe

 

theirs no way to tow in 5th with a early g56 2500 @ 60. it would be nice t know what was done to get the ratio different tho

 

It doesn't matter if you have a NV5600, early G56 or late G56, 5th is 1:1 on ALL of them.. if they all have 3.73's then they all will be at the same rpms at the same speed, on the same tires.

 

well then my trucks a freak 3:73's and at 60 she does turn alittle under 2500 rpm in 5th 1900 in 6th tires are factory size

 

I didn't notice it until now but those numbers don't match... 2200 rpms in 5th is only 54mph, or 87 kph.. 100kph/62mph is actually 2550 rpms... Which IMHO it too much to continually tow at.

So thats why anyone would tow in 6th. At 60mph I don't want to run 2500 rpms, but 1800 is plenty for most hills... 65mph is even better in 6th at 1950rpms.

In order for 2200 rpms to 100 kph in 5th then you either have to have tires with a 35.5" rolling diameter (about a 36-37" tire), or 3.25 gears... even 3.42 gears is only 95kph at 2200.

Not a freak, factory size tires, 3.73's, and 5th should be 61mph at 2500. 6th should be 1939 on an early G56.

 

www.jl4c.org/dtr/tires/tirecalc.zip

 

Not bad, but the ones that use rev/mile data are a little more accurate.. As the OEM 265/70/17 calculates out to 31.6" tall, but only rolls at 30.7".

 

Exactly, the awesomely tall 1st gear is great for crawling and gives the early G56 trucks a crawl ratio > 60:1.

-Chris