Wide ratio c6 with 3.00 axle

[jbass020]

Anyone out there have experience with a wide ratio conversion and taller gears (3.00 or taller)?
My current setup is a 4 brl 390/c6, 3.25 axle, and 235/75 15 tire
It drives the highway OK at 55-60
Curious, would the wide ratio balance out a taller rear gear for towing?

[jbass020]

The AOD or E4OD gearset is what I had in mind.
If I understand it correctly, the final drive ratio is a combination of th transmition, rear axle, and tire size. For my application the tire size would not be changed.
So:

C6 ratios: 2.46, 1.46, 1
with 3.25 axle: 7.995, 4.745, 3.25
E4OD conversion: 2.71, 1.538, 1
With 2.91 axle: 7.886, 4.475, 2.91

Theoretically, this places first gear at about the same place, while lowering the final.
If my math is correct, at 65 mph the rpm should drop from 2531 to 2266.

Is it worth it?

Now my head hurts

[Donnie]

First & 2nd are the only gear change that this conversion will improve..3rd will remain the same, Direct--one in & one out.. as you can see the change is minimal & myself, I can't think that it is worth it, but only you can decide that. If you need a lower boost pulling out, this will help..
You have already run the numbers, if you change your rear end gears, this mod will help you get moving, but on the road????????????????? ..............Donnie

Think this one thru, as it is a lot of work for a small gain...again, that's just my opinion

[70_F100]

Before I'd go to all of that trouble, if you're wanting the 2.91 rear, go ahead and change it.

You might find that it works well leaving the transmission as-is.

On the other hand, if you still think you need to do the tranny mod, well, it sounds like you're already planning it, so do it after the rear gear swap.

Worst case scenario, you have to do everything you planned. Best case, you've saved yourself a lot of trouble and are happy with the original tranny setup.

[Donnie]

70-100 is correct..........3;25 & 2:91 are pretty close....not a lot of gain here either???
..........................Donnie

[Kurt Combs]

I just changed my tires from 225/65/16 to 265/65/16 (1972 F-250 with a 360) and I am running 3:5? rear gears. I lost acceleration on hills at high speeds, but I don't notice any problems in the lower gears. It is probably a little slower off the line, but what I miss is accelerations on the highway. I would recommend you figure out what size tire will give you the final drive ratio you expect with the gear change, and put some used tires on your truck of that size and see if you like it. I was surprised by the difference.