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More road speed

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I would like to get more road speed and lower my rpm's. I have a '82 R Model with 3.65 rears and a 5 speed transmission. According to the speedometer it is running 62 to 65 at 2000 rpm's. Which transmission could I put in it to get more road speed at lower rpm's. I would like to run 70-75 at 1500 rpm's. Also I need a low hole to start off on a hill loaded 80,000+. I'm asking the experts on this one. Thanks.

Edited by jrbnelson

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Be carefull in your thinking cause you may need more HP for speed.

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I would agree with theakerstwo and J. hancock. Need specs. But what you could do is put a 10 or a 13 speed in, gear it lower like 3.90,4.11. That will make up for lack of power on tall rubber and still get you down the road. or try an 8LL or a 9LLthey usually have really long legs and good low end and think about gearing it lower to compensate on drag and more gears. Also stay away from a 15 speed. You need a big horse in high gear to keep it wound up

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I would like to get more road speed and lower my rpm's. I have a '82 R Model with 3.65 rears and a 5 speed transmission. According to the speedometer it is running 62 to 65 at 2000 rpm's. Which transmission could I put in it to get more road speed at lower rpm's. I would like to run 70-75 at 1500 rpm's. Also I need a low hole to start off on a hill loaded 80,000+. I'm asking the experts on this one. Thanks.

If you are on 22.5, high tred tires and run 62 to 65 i bet you have 4.17 or 3.87. i dout you have 3.65 with a 5 speed unless someone installed them, that thing would be gutless. Ron

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I agree, something sounds off. check your specs.....with 4.10 and 22.5 with a 15speed O.D. we are running 1800rpm at 62mph.

Your 5 spd should have a nice overdrive.

Sounds to me you may have 4.50 rears with 24.5 tires or 22.5 tires with 4.17

Just guessing there.

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Any overdrive with a .86 will bump your mph from 62 to 72.1 (at same RPM) regardless of what rear ratio you have. T200 Macks would be way too fast. Many Roadrangers had the .86 overdrive. You'll also need to look for a Mack bellhousing to make the Roadranger work.

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It has 22.5 tall rubber. The stamp on the rear housing has 3.65 on it. I checked the numbers on the rearend housing and the build sheet and all the numbers match. Unless the speedometer is off that much. Does a Mack ratio run the same as a eaton. My Kenworth has an 18 speed and 3.70 and it will run 75 at 1600. Thanks for all the replys

Edited by jrbnelson

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It has 22.5 tall rubber. The stamp on the rear housing has 3.65 on it. I checked the numbers on the rearend housing and the build sheet and all the numbers match. Unless the speedometer is off that much. Does a Mack ratio run the same as a eaton. My Kenworth has an 18 speed and 3.70 and it will run 75 at 1600. Thanks for all the replys

Your comparing apples to Oranges. the K.W. Probably has min 500 horse. taller od. A 5 speed with a 300 will roll down the road if it is a 3.65 just forget about low end

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You have a 5 speed that is direct in 5th. You need an over drive trans. Look for an 8LL or a Mack 12 speed. Both have wide splits for the maxidynes torque curve and a over drive that can get you home in a hurry. That's my .02

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Lmackattack you got it right on the 5 speed direct. The build sheet has the truck set up to run 59 mph. I really don't like a 12 speed. Did mack make an 8LL. Slpwlker the 18 speed and 3.70 was used to ask if Mack rear ratios were close to eatons. Example 3.65 Mack close to 3.70 eaton.

Edited by jrbnelson

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The 8 LL is eaton??. It's not as strong as a Mack 12 but the splits are wide and the 300 maxidynes loves that.

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I would like to get more road speed and lower my rpm's. I have a '82 R Model with 3.65 rears and a 5 speed transmission. According to the speedometer it is running 62 to 65 at 2000 rpm's. Which transmission could I put in it to get more road speed at lower rpm's. I would like to run 70-75 at 1500 rpm's. Also I need a low hole to start off on a hill loaded 80,000+. I'm asking the experts on this one. Thanks.

In the 80s many of us where putting 13spd's with the 3.65s and 3.87s to help torque load on the bullgear and the 2 step overdrive help with the 300 stay in the power band with this tall of a rear........but back then first and reverse where not very low for take off on a hill and Mack didn't have a two step overdrive then..

Mack does have a nice one now...... look at a 3113LR21

If you had 4.42s or 4.64s the Mack or Fuller 8spd would be good combo

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thanks for the reply mackcl96 i'll look into the mack 13 speed.

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