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 yesterday at 02:06 PM Share Posted yesterday at 02:06 PM 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 16 hours ago Author Share Posted 16 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 15 hours ago Share Posted 15 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 15 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 13 hours ago Author Share Posted 13 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 4 hours ago Share Posted 4 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 4 hours ago Share Posted 4 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 2 hours ago Share Posted 2 hours 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 2 hours ago Share Posted 2 hours 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...
Geoff Weeks Posted 1 hour ago Share Posted 1 hour ago 23 hours ago, terry said: 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 11 hours ago, Flying Pig said: 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. The issue @terry and I are trying and failing to get across, is that an engine built to run in front of a close ratio 9 sped is fundamentally a different engine than one built to run in front of a wide ratio transmission. The 350 and 9 spd has higher torque and hp but in a narrower band than a 300 designed to work with a wide ratio box. Maxidyne vs Econodyne. I hope showing the Charts for the two types would get the point across. While placing a broad torque band engine in front of a close ratio trans will do no harm but not use the engine to its best, going the other way (placing a narrow torque band engine in front of a wide ratio box) can do some serious damage as the engine will lug at every gear change and may never have enough torque to make it into the power band of the gear it is in. 2 Quote Link to comment https://www.bigmacktrucks.com/topic/76520-9-to-8-speed/#findComment-593754 Share on other sites More sharing options...
terry Posted 1 hour ago Share Posted 1 hour ago As geoff said, i had a 285 which is a engine you can lug down to about 1100 or 1200 RPM's i had it with a mack 12 speed and loved that combination. terry 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76520-9-to-8-speed/#findComment-593756 Share on other sites More sharing options...
fjh Posted 1 hour ago Share Posted 1 hour ago My self I would install an 18 sp fuller more selection is in my mind always best regardless of engine band width ! More choices! That said if you already got that trans then its up to you! Also In my area the 18 is more widely available! Quote Link to comment https://www.bigmacktrucks.com/topic/76520-9-to-8-speed/#findComment-593757 Share on other sites More sharing options...
Freightrain Posted 1 hour ago Share Posted 1 hour ago 12 minutes ago, terry said: As geoff said, i had a 285 which is a engine you can lug down to about 1100 or 1200 RPM's i had it with a mack 12 speed and loved that combination. terry My 237 worked well with Triplex. It could pull down, but seemed better with tighter splits available. Granted I am not pulling 80k lbs. My 300+ had a 5 spd behind it. I know the transmission was original to the truck but not sure the engine was. I bet it was a dog with only 5 gears. Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/76520-9-to-8-speed/#findComment-593758 Share on other sites More sharing options...
terry Posted 1 hour ago Share Posted 1 hour ago 4 minutes ago, Freightrain said: My 237 worked well with Triplex. It could pull down, but seemed better with tighter splits available. Granted I am not pulling 80k lbs. My 300+ had a 5 spd behind it. I know the transmission was original to the truck but not sure the engine was. I bet it was a dog with only 5 gears. Yeah before my285 and 12 speed, my truck had a237 and a quad, liked that too, but that quad was a no no on lugging way down. hard on that single countershaft trans. terry Quote Link to comment https://www.bigmacktrucks.com/topic/76520-9-to-8-speed/#findComment-593759 Share on other sites More sharing options...
Freightrain Posted 29 minutes ago Share Posted 29 minutes ago I didn't take mine below 1500. Maybe 1400 if I was easing off the throttle before downshifting. Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/76520-9-to-8-speed/#findComment-593763 Share on other sites More sharing options...
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