mackr1989 Posted October 21, 2014 Share Posted October 21, 2014 Preferences Preferencwewe're getting a 30k rear axle for our 6 wheel dump. it currently has 22.5 rubber, 6 speed low hole tranny, 250 motor and differential ratio of 4.00. it tops out at about 62 mph at 2100 rpms. i can get this axle with either a 3.90 or a 4.10. it often pulls a 20 ton tag. will the 3.90 add more speed and if so how much? how much lower end power will we lose? the only thing im worried about with the 4.10 is it will be to slow. i know either ratio is only a 10th higher or lower than what we have. i just want to know which would be best. the axle is complete and our 22.5 wheels will fit. Preferences§1234567890-=Backspace Tabqwertyuiop[] Return capslockasdfghjkl;'\ shift`zxcvbnm,./shift English Deutsch Español Français Italiano Português Русский altalt Preferences Quote Link to comment https://www.bigmacktrucks.com/topic/37440-390-or-410-gear-ratio/ Share on other sites More sharing options...
j hancock Posted October 21, 2014 Share Posted October 21, 2014 3.90 64 mph. Not gaining much.4.00 62 mph.4.10 61 mph. Not loosing much. Quote JimIt doesn't cost anything to pay attention. Link to comment https://www.bigmacktrucks.com/topic/37440-390-or-410-gear-ratio/#findComment-263939 Share on other sites More sharing options...
mackr1989 Posted October 21, 2014 Author Share Posted October 21, 2014 Does anyone know the equation to figure out speed? Quote Link to comment https://www.bigmacktrucks.com/topic/37440-390-or-410-gear-ratio/#findComment-263959 Share on other sites More sharing options...
Vladislav Posted October 21, 2014 Share Posted October 21, 2014 If you have current figures just make a proportion. Divide the "new" ratio by the current, than multiply you curren top speed with the result.So will see the increase or decrease.If you prefere sharp figures you need to count out your wheel's one rev length (3.14xOD), and being known how many revs the engine does (2100 per MINUTE) you continue dividing them by overall drivetrain ratio (0.60 overdrive in T2060 tranny multiplied with 4.00 in rears). After dividing 2100/(0.60x4.0) = 875 you get the number of revs of the wheel per minute (875). Than knowing how long way your wheel makes by every revolution (don't know what 22.5's they are) you multiply it with 875 and get the way the truck makes in one MINUTE. Than divide it by 60 and see the way in one hour. But... If you count the wheel's circle length in inches you will get the speed in INCHES per hour. So you'll need to divide it by the number of inches in a mile to see the top speed by common way. Sorry I'm not ready to tell you how many inches in a mile is, I'm used to live in the metric world Quote Никогда не бывает слишком много грузовиков! leversole 11.2012 Link to comment https://www.bigmacktrucks.com/topic/37440-390-or-410-gear-ratio/#findComment-263963 Share on other sites More sharing options...
j hancock Posted October 21, 2014 Share Posted October 21, 2014 (Rpm X tire diameter) divided by (gear ratio X 336) = mphUsing your trucks info.(2100 rpm X 40") divided by (4.00 rear ratio X 336) = 62.5 mph 2 Quote JimIt doesn't cost anything to pay attention. Link to comment https://www.bigmacktrucks.com/topic/37440-390-or-410-gear-ratio/#findComment-263964 Share on other sites More sharing options...
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