Freightrain Posted April 9, 2021 Share Posted April 9, 2021 Just doing quick math the change from 4.42 to 4.17 will drop you 100 rpm. 4.17/4.42 = .94%. Your 65 mph at 1700 rpm x .94% = 1598 rpm. Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/66472-12spd-and-417-rear/page/2/#findComment-472295 Share on other sites More sharing options...
fjh Posted April 9, 2021 Share Posted April 9, 2021 Most of the changes in gearing here we used to do was to change to 4.64 due to the V8 ! Anything over 400 would eat the 4:17/ 4:42 ratios for breakfast in the offroad type settings here! lots of hills! Used rebuild lots of these top gear sets would pit out and break! the above ratios were a simple top gear set change! 1 Quote Link to comment https://www.bigmacktrucks.com/topic/66472-12spd-and-417-rear/page/2/#findComment-472304 Share on other sites More sharing options...
Brian L Blaylock Posted April 11, 2021 Share Posted April 11, 2021 My Superliner with a 12 speed overdrive 4.17 rear ends and 11-24.5 tires runs out at about 85 with the engine turning 2000 rpms 2 Quote Link to comment https://www.bigmacktrucks.com/topic/66472-12spd-and-417-rear/page/2/#findComment-472368 Share on other sites More sharing options...
mrsmackpaul Posted April 11, 2021 Share Posted April 11, 2021 I just calculated what I do, you dont wanna see my results Give you speedy buggers nightmares lol Paul 1 Quote Link to comment https://www.bigmacktrucks.com/topic/66472-12spd-and-417-rear/page/2/#findComment-472371 Share on other sites More sharing options...
Hayseed Posted April 11, 2021 Share Posted April 11, 2021 5 hours ago, mrsmackpaul said: I just calculated what I do, you dont wanna see my results Give you speedy buggers nightmares lol Paul You could just about pull Christ off the Cross with That Paul... Quote "Be who you are and say what you feel...Because those that matter...don't mind...And those that mind....don't matter." - Link to comment https://www.bigmacktrucks.com/topic/66472-12spd-and-417-rear/page/2/#findComment-472379 Share on other sites More sharing options...
mrsmackpaul Posted April 11, 2021 Share Posted April 11, 2021 Or the ass out of the ocean lol Well thats why these old trucks are rated to 115 ton (215000 pounds) from new Originally had 5.73's someone pointed out to me a while that they had been changed as they are stamped 5.29 Paul Quote Link to comment https://www.bigmacktrucks.com/topic/66472-12spd-and-417-rear/page/2/#findComment-472401 Share on other sites More sharing options...
Bliue dm Posted April 13, 2021 Author Share Posted April 13, 2021 If my grandfather had an old quad that ran 62mph. That was flying then. Quote Link to comment https://www.bigmacktrucks.com/topic/66472-12spd-and-417-rear/page/2/#findComment-472465 Share on other sites More sharing options...
Dirtymilkman Posted April 26, 2021 Share Posted April 26, 2021 Run 3.86's, if you feel after that it isn't enough torque, switch to lo pros. Quote Link to comment https://www.bigmacktrucks.com/topic/66472-12spd-and-417-rear/page/2/#findComment-472986 Share on other sites More sharing options...
Steve L Posted June 12, 2021 Share Posted June 12, 2021 I used to pull around 100 tons (don’t know what that is lbs) with a 237 F model 6 speed with 4.17s and never had a problem. So I’m sure it would do it easy Bliue Quote Link to comment https://www.bigmacktrucks.com/topic/66472-12spd-and-417-rear/page/2/#findComment-475135 Share on other sites More sharing options...
blackdog2 Posted June 12, 2021 Share Posted June 12, 2021 55 minutes ago, Steve L said: I used to pull around 100 tons (don’t know what that is lbs) with a 237 F model 6 speed with 4.17s and never had a problem. So I’m sure it would do it easy Bliue Short ton 200,000 lbs......long ton 224,000 lbs ... 1 Quote Ed Link to comment https://www.bigmacktrucks.com/topic/66472-12spd-and-417-rear/page/2/#findComment-475137 Share on other sites More sharing options...
Vladislav Posted June 12, 2021 Share Posted June 12, 2021 On 4/11/2021 at 11:40 PM, mrsmackpaul said: Or the ass out of the ocean lol Well thats why these old trucks are rated to 115 ton (215000 pounds) from new Originally had 5.73's someone pointed out to me a while that they had been changed as they are stamped 5.29 Paul I never heard about Mack 5.29 diffs. They were 5.32 or 5.13. If a real interest I'd jack up a tyre and count the prop shaft revs after spinning the wheel 10 or 20 turns. Another way is removing that big side cover off a carrier and make the teeth count. Sharp method but the issue you only can see the top gear set. No access to the bull gear excepting removing the carrier off the banjo. Quote Никогда не бывает слишком много грузовиков! leversole 11.2012 Link to comment https://www.bigmacktrucks.com/topic/66472-12spd-and-417-rear/page/2/#findComment-475147 Share on other sites More sharing options...
mrsmackpaul Posted June 13, 2021 Share Posted June 13, 2021 5 hours ago, Vladislav said: I never heard about Mack 5.29 diffs. They were 5.32 or 5.13. If a real interest I'd jack up a tyre and count the prop shaft revs after spinning the wheel 10 or 20 turns. Another way is removing that big side cover off a carrier and make the teeth count. Sharp method but the issue you only can see the top gear set. No access to the bull gear excepting removing the carrier off the banjo. Vlad you are possibly correct They were 5.73 when new, the carrier has 5.29 stamped on the top of it so I have just assumed that is what they are I did have that big cover off only months ago as it was weeping around it and replaced the O ring, or maybe gasket goo, dunno now Anyway that is my understanding, 95 km/h is revving pretty hard That is on the GPS thingy mahbob Paul Quote Link to comment https://www.bigmacktrucks.com/topic/66472-12spd-and-417-rear/page/2/#findComment-475158 Share on other sites More sharing options...
Vladislav Posted June 17, 2021 Share Posted June 17, 2021 On 6/13/2021 at 5:14 AM, mrsmackpaul said: Vlad you are possibly correct They were 5.73 when new, the carrier has 5.29 stamped on the top of it so I have just assumed that is what they are I did have that big cover off only months ago as it was weeping around it and replaced the O ring, or maybe gasket goo, dunno now Anyway that is my understanding, 95 km/h is revving pretty hard That is on the GPS thingy mahbob Paul Paul, if you ever have one of those big covers off again it would be a good activity to take a piece of pencil and paper and write the number of teeth each of the gears of the top set has. You can't count the lower set teeth as I pointed but having the top set figures you can "count out" the ratio knowing existing combo's. Just let me know if you have any interest in the figuring. 1 Quote Никогда не бывает слишком много грузовиков! leversole 11.2012 Link to comment https://www.bigmacktrucks.com/topic/66472-12spd-and-417-rear/page/2/#findComment-475380 Share on other sites More sharing options...
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