Gears are Ordered

[BarronTG]

His is a diesel. I would go .410

Thanks guys. Correct, I have a Cummins. I had 4.10 in mind, but wanted to see if I was thinking correctly. I currently have 35x13.5x20, with 12" wide rims. How bad am I straining the 68 trans with this setup (3.42 gears)? Think I can hold off gear swapping until my next tire size jump? I want more tire ballooning next go around, so am thinking of 37x15.5x20. I'll definitely have more weight/resistance than I do now, and with the delete, more power. I don't wanna send the 68 to the grave... Until this thread, I didn't realize how expensive the great swap was. Guess I better get saving up!

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[BarronTG]

Man y'all are on it, thanks a bunch!

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[mtnrider]

Edit: Just did the calculations and 4.56 on a 37 (36.5”) nets a cruising Rpm of 1900 between 70&75.

That's getting up there in RPM for a diesel. I wouldn't want to be cruising at highway speeds regularly with 4.56's. Your mpg is really going to suck. Around town and towing heavy it would be good though.

I think 4.10 would be the best option unless you do no highway driving. 4.10 with 37's still gets you a lower overall ratio then a stock truck/tires with 3.42's.

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[mtnrider]

Thanks guys. Correct, I have a Cummins. I had 4.10 in mind, but wanted to see if I was thinking correctly. I currently have 35x13.5x20, with 12" wide rims. How bad am I straining the 68 trans with this setup (3.42 gears)? Think I can hold off gear swapping until my next tire size jump? I want more tire ballooning next go around, so am thinking of 37x15.5x20. I'll definitely have more weight/resistance than I do now, and with the delete, more power. I don't wanna send the 68 to the grave... Until this thread, I didn't realize how expensive the great swap was. Guess I better get saving up!

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I'm pretty sure you can kiss that transmission goodbye before too long. They do not like that added power and if you start getting "frisky" with the truck it's a goner for sure. Even with a gear swap you are going to need to be careful with it. There are guys killing those transmission that are on stock(ish) tires. They just don't like the added power.

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[BarronTG]

That's getting up there in RPM for a diesel. I wouldn't want to be cruising at highway speeds regularly with 4.56's. Your mpg is really going to suck. Around town and towing heavy it would be good though.

I think 4.10 would be the best option unless you do no highway driving. 4.10 with 37's still gets you a lower overall ratio then a stock truck/tires with 3.42's.

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And I do a lot of hwy cruising. 4.10 for the win

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[68PowerWagon]

Wonder why there is a break in period on the after market gears? As far as I know there is only a mild break in period for the engine off the assembly line. Another question for anyone who has done a gear swap... what size is the rear end on the 4th gen 2500 6.4? 11.25 or 11.50? I am wanting to put some Big Diesel aluminum covers on when I swap & in the same advertisement they have both numbers down. I wanna say the 11.25 are for the 2500 regardless of Hemi or Cummins but the 3500 gets the 11.5"

 

[Mountaineer83]

The 2500 has the 11.5" rear. The single rear wheel 3500 does as well, then jumps to the 11.8" in the 3500 dually. Someone correct me if I'm wrong!

 

[FlatbedHemi]

Wonder why there is a break in period on the after market gears? As far as I know there is only a mild break in period for the engine off the assembly line. Another question for anyone who has done a gear swap... what size is the rear end on the 4th gen 2500 6.4? 11.25 or 11.50? I am wanting to put some Big Diesel aluminum covers on when I swap & in the same advertisement they have both numbers down. I wanna say the 11.25 are for the 2500 regardless of Hemi or Cummins but the 3500 gets the 11.5"

I asked the same question to guys at my shop, and they had asked the same questions to their gear rep. The only thing they could come up with is that the axels are likely subjected to a breakin before going under the trucks. No way to confirm this without conferring with someone from the assembly plant I guess.