Flying Pig Posted Wednesday at 02:48 AM Share Posted Wednesday at 02:48 AM I’m looking at a truck with a Mack 9 speed. Can I swap in an 8 speed in the same place. Is there any difference in length between the two? Quote You'll never go wrong by doing right. Who do you call when the lawmakers ignore the law? Link to comment https://www.bigmacktrucks.com/topic/76520-9-to-8-speed/ Share on other sites More sharing options...
terry Posted Wednesday at 04:59 AM Share Posted Wednesday at 04:59 AM What make of eight speed mack or fuller? terry 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76520-9-to-8-speed/#findComment-593661 Share on other sites More sharing options...
Flying Pig Posted yesterday at 04:11 AM Author Share Posted yesterday at 04:11 AM Mack please. Wondering if the 8 speed is the same overall length or if a different length driveshaft is needed. The 8 speed has lower low gear ratios which would suit the job better. I’m sure the 9 speed would work ok, but the lower gear would be better. Quote You'll never go wrong by doing right. Who do you call when the lawmakers ignore the law? Link to comment https://www.bigmacktrucks.com/topic/76520-9-to-8-speed/#findComment-593705 Share on other sites More sharing options...
880joe Posted yesterday at 10:31 AM Share Posted yesterday at 10:31 AM The 8 speed will also have a higher overdrive ratio 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76520-9-to-8-speed/#findComment-593706 Share on other sites More sharing options...
Flying Pig Posted yesterday at 11:21 AM Author Share Posted yesterday at 11:21 AM I am wanting that too. I built a custom Fuller with a .6 of but I only use it when empty. The Mack I’m looking at will be geared lower than my Ford. Quote You'll never go wrong by doing right. Who do you call when the lawmakers ignore the law? Link to comment https://www.bigmacktrucks.com/topic/76520-9-to-8-speed/#findComment-593709 Share on other sites More sharing options...
terry Posted 23 hours ago Share Posted 23 hours ago The only drawback is the engine infront of the nine speed is not made to be lugged down like it will be with the mack eight speed transmission, terry Quote Link to comment https://www.bigmacktrucks.com/topic/76520-9-to-8-speed/#findComment-593714 Share on other sites More sharing options...
Flying Pig Posted 15 hours ago Author Share Posted 15 hours ago Terry, Where would the lugging come from? Lower low gear will let me use a little rpm while still going slow. Quote You'll never go wrong by doing right. Who do you call when the lawmakers ignore the law? Link to comment https://www.bigmacktrucks.com/topic/76520-9-to-8-speed/#findComment-593723 Share on other sites More sharing options...
Geoff Weeks Posted 13 hours ago Share Posted 13 hours ago (edited) Wider ratio gap between gears, means the engine speed may be too low for the load in the next higher gear but too high in the present gear. Torque rise of the engine has to be matched to the gears available. An engine set up for a 9 speed with closer steps will not be matched to a transmission with wider steps. Edited 13 hours ago by Geoff Weeks Quote Link to comment https://www.bigmacktrucks.com/topic/76520-9-to-8-speed/#findComment-593736 Share on other sites More sharing options...
Flying Pig Posted 11 hours ago Author Share Posted 11 hours ago I guess I’m at a bit of a loss. A 300 can use a 5,6,7 or 8 speed but a 350 can’t? The 350 would have more torque. Please help me understand. Quote You'll never go wrong by doing right. Who do you call when the lawmakers ignore the law? Link to comment https://www.bigmacktrucks.com/topic/76520-9-to-8-speed/#findComment-593743 Share on other sites More sharing options...
Joey Mack Posted 3 hours ago Share Posted 3 hours ago Quote Link to comment https://www.bigmacktrucks.com/topic/76520-9-to-8-speed/#findComment-593747 Share on other sites More sharing options...
Joey Mack Posted 3 hours ago Share Posted 3 hours ago I thought I would post these to help you know the ratios. Quote Link to comment https://www.bigmacktrucks.com/topic/76520-9-to-8-speed/#findComment-593748 Share on other sites More sharing options...
Geoff Weeks Posted 1 hour ago Share Posted 1 hour ago 1 hour ago, Joey Mack said: I thought I would post these to help you know the ratios. I think what he needs help with is the torque rise of the engine in question, and why some need close ratio steps and others in the Mack family can work with wide ratio steps. The engine torque rise has to work with the steps between gears. You know Mack engines better than I and can advise. Quote Link to comment https://www.bigmacktrucks.com/topic/76520-9-to-8-speed/#findComment-593752 Share on other sites More sharing options...
Joey Mack Posted 49 minutes ago Share Posted 49 minutes ago If he posts the engine he has, theres a good chance i have the charts. Quote Link to comment https://www.bigmacktrucks.com/topic/76520-9-to-8-speed/#findComment-593753 Share on other sites More sharing options...
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