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13sp double over with 2:64

I have an 06 C13 with a 13spd double over and 3:73 rears. I have a set of 2:64s on the shelf and am wondering if I can put those with a double over and what kind of performance I could expect.

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With that setup you would want to run about 65mph in 11gear, which would be direct drive. 12th would be for speeds over 70 and 13th would be just about worthless. If you drive this truck around 65mph in 11 gear there should be a 3% fuel improvement over running at the same speed in an overdrive. Do you know the model number of the transmission? Probably now you start out in like 2nd or 3rd gear, when you switch to the 2:64 your going to want to start out mostly in 1st and 2nd gear, but I think it will be ok. I'm doing something similar myself. I'm switching from 3:73 to 2:79 with a 10 spd overdrive and planning to run 58mph in 9th gear. Keep us posted on how you make out.

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I have my truck governed at 69 and generally stay around 63-65. I had a truck that a driver wrecked and was able to save the rears. The 10sp direct drive was blown apart all over the highway so was just wondering if it would be worth the swap.

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I have been using a 18 speed with 2.64 for about 2.5 years now. I would not consider a 13 with 2.64 unless I was running light all the time. There are just too many instances, when heavy and on an incline, that splitting the bottom is necessary on take off. An 18 also has much deeper bottom reduction than a 13 which can come in handy on softer ground. A 13 tied to 2.64 wouldn't be my first choice of a trans and rear ratio match up. Look at what you are doing, the situations you get in to, and make an informed decision. For what I do, if I was using a 13, I would consider 3.08. Same as 2.64, just puts you in the first OD at the same road speed, which is still more efficient than running in second OD.

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If you do this I would hold on to the 13 speed in case you don't like this setup you can put it back in. If you don't put it back in I might be interested in it depending on make and model

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I had a 13double over with 3:55 and couldn't touch the final gear unless I was running down hill so that part of the tranny is use less but it did run good in direct. Can't remember the fuel mileage cause it was back in the day.

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When changing to 2.64 ratio did it bother reverse backing into docks and such

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When you change to 2.64 will it bother reverse backing into docks and such

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Well, 419,000 miles on my truck with 18 speed and 2.64 rear ratio, and I have not had any issues backing in anywhere. Low side of reverse, even with 2.64, you are not off to the races. Frankly, I really haven't been able to tell any difference backing than when I had 3.42 in the previous truck. That includes that demanding type of backing in the caves around Kansas City. Been in there several times with this truck and have never felt that the 2.64 made anything difficult. A 13 would be identical as far as backing is concerned.

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Running 2.64 gears (or 2.79) has anybody been pulling more than 80K. In the summer I run RM doubles at 117K and don't know if these gears will work. I currently have 3.55s and was thinking of going to 3.70.

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starlytxprs1 will be eternally grateful.
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