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So after selling both my r model dump and roll off a few years ago, I very quickly started missing them and looking for another. My perfect truck would be heavy spec short wheelbase dump. A Tandem with 58 rears 18 or 20 front, 350 or more hp and a good trans. Well, I just purchased a 86 RD600 in decent shape and well kept. heavy spec, but a little less hp then I wanted having the em-300. I actually don't mind the 300 hp with the torque it puts out and knowing its durabilty, but my real complaint is the 7 speed T2070 trans. Great low end power and great highway speeds, but really wish i had more gears to split to get it to speed. I feel like i am making the motor work to hard with heavy loads (70,000 lb). Was really hoping to swap out for maybe a mack 12, 13, or 18 speed. Any suggestions? 

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1 hour ago, Anthony All Site said:

So after selling both my r model dump and roll off a few years ago, I very quickly started missing them and looking for another. My perfect truck would be heavy spec short wheelbase dump. A Tandem with 58 rears 18 or 20 front, 350 or more hp and a good trans. Well, I just purchased a 86 RD600 in decent shape and well kept. heavy spec, but a little less hp then I wanted having the em-300. I actually don't mind the 300 hp with the torque it puts out and knowing its durabilty, but my real complaint is the 7 speed T2070 trans. Great low end power and great highway speeds, but really wish i had more gears to split to get it to speed. I feel like i am making the motor work to hard with heavy loads (70,000 lb). Was really hoping to swap out for maybe a mack 12, 13, or 18 speed. Any suggestions? 

yes a real quick answer, to run the 12,13, or 18 you have to change rear ends, that T2070 is run with about a 5.50 rear. know if you change to a 4.17 rear you will have a real runner, but your kind of under powered with the 300 horses.    terry:MackLogo:

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Had the same setup in a truck we grossed 85,000 pounds with for years. Quite a stretch between gears but once you get her going it hauls. Don't switch tranny unless you plan on switching rears too. 

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I have the same combo and  run 76500  good on fuel but takes awhile to get use to .

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T2070 has 0.60 top hole. The same for T2060 and T2080. T2090, T2110, T2130 and T2180 all have 0.71. That's why you would like faster rears if go to the most any multi speed transmission.

Actually you should count T2070 as a 5-speed (T2050) with two crawl gears. The same for T2060 and T2080 with one and three crowls. They were designed for vocational jobs the most to eliminate shifs in traffic. The additional low speeds spreaded the use toward construction jobs when you operate a dump, mixer or concrete pump chassis driving in a city but need really low speeds for special tasks.

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