superliner237 Posted September 22, 2013 Share Posted September 22, 2013 howdy! just a quick question. I was doin the math on some gear ratios vs. speed and r.p.m,s. will the math be the same between eaton-spicer type rears and mack rears. Mine are 38000 or 40000 lb. example---- my 4.42 gears figure same as lets just say 4.42 eatons? someone told me they did the math different with the macks. thanks for any info u guys have. Quote Link to comment https://www.bigmacktrucks.com/topic/32884-mack-gear-ratios/ Share on other sites More sharing options...
j hancock Posted September 22, 2013 Share Posted September 22, 2013 Not that I have heard.You will also need tire size and know your overdrive ratio to do your calculations. Quote JimIt doesn't cost anything to pay attention. Link to comment https://www.bigmacktrucks.com/topic/32884-mack-gear-ratios/#findComment-207862 Share on other sites More sharing options...
Timmyb Posted September 23, 2013 Share Posted September 23, 2013 I'm pretty sure mack rears are different. I've got a chart that you can work out what ratio diffs will work with the ration of your overdrive. My mack 10 speed has an overdrive of .78 so using this chart I can safely assume what ratio I need. https://ne1-attach.ymail.com/au.f1251.mail.yahoo.com/ya/securedownload?fid=Inbox&mid=2_0_0_1_76745_APNoimIAABJjUj%2FehQAAAJSsIA8&pid=2&check_content_type=2&fullscan=1&YY=377702796&appid=YahooMailMobile&cred=9HhWTu6RV17.NmffrfoIlUGUgKU_iolKVY4pNVfFgE6f75s-&ts=1379917991&partner=ymail&sig=MgaDgnrz567b3sl8BEE33A--Hope that helps mate! Quote Link to comment https://www.bigmacktrucks.com/topic/32884-mack-gear-ratios/#findComment-208078 Share on other sites More sharing options...
Timmyb Posted September 23, 2013 Share Posted September 23, 2013 Sorry wrong link, try searching "106042 speed chart" Quote Link to comment https://www.bigmacktrucks.com/topic/32884-mack-gear-ratios/#findComment-208080 Share on other sites More sharing options...
Timmyb Posted September 23, 2013 Share Posted September 23, 2013 Took some screen shots in case you couldn't find it Quote Link to comment https://www.bigmacktrucks.com/topic/32884-mack-gear-ratios/#findComment-208081 Share on other sites More sharing options...
j hancock Posted September 23, 2013 Share Posted September 23, 2013 If a Mack carrier says it is a 4.17 (for example), it is a 4.17. 1 Quote JimIt doesn't cost anything to pay attention. Link to comment https://www.bigmacktrucks.com/topic/32884-mack-gear-ratios/#findComment-208088 Share on other sites More sharing options...
VALS327 Posted September 23, 2013 Share Posted September 23, 2013 Hello,I enclosed a link that makes it real simple. Just plug in your numbers hit compute and it does the math for you.http://www.angelfire.com/fl/procrastination/rear.html Quote Link to comment https://www.bigmacktrucks.com/topic/32884-mack-gear-ratios/#findComment-208090 Share on other sites More sharing options...
RowdyRebel Posted September 24, 2013 Share Posted September 24, 2013 If you've got a 4.42 rear gear ratio, it doesn't matter if it is Mack, Eaton, Rockwell, or any other manufacturer...the drive shaft will spin around 4.42 times for every 1 time the tires go around. In a simple differential, it is just the ratio of teeth on the ring gear to the number of teeth on the pinion gear, but in a double-reduction rear end the math gets a little more complex. Same idea, though...no more than a numerical expression of the relationship between the rotational speeds of the drive shaft and the axle shafts. Quote When approaching a 4-way stop, the vehicle with the biggest tires has the right of way! Link to comment https://www.bigmacktrucks.com/topic/32884-mack-gear-ratios/#findComment-208108 Share on other sites More sharing options...
superliner237 Posted September 24, 2013 Author Share Posted September 24, 2013 just got back 2 check the info u guys came back with. thanks for all the answers. makes sense that a 4.42 ratio is 4.42 ratio no matter what brand rears. just double checkin. did the math on our t-600 k-dub and when we got it all put together it came out spot on. then feelin all good abut things i did the math on the mack and came up with an idea of what to do with him, then i was told that macks were calculated different. didn't think so but started to second guess things. so before i went and bought parts i had better know 4 sure. the boss is pretty good at lettin me do my thing but too big of a f-up would put him over the edge. my thoughts on this trk...has a 350 4 valve am-bosch pump, 2090 old shift patt. trans with what i believe 2b a .71 o.d. , 4.42 gears and i plan on jumpin up to 24.5 talls(11.00) should put me around the 1600 r.p.m range at 65. low hole is gonna b fine i think for loaded starts. ran this trk for years hauling pulp wood with the 98000 permit translated to 100000 plut more than a few times and this trk did great. just a bit and i mean just a bit slow on the big roads. now its going to run o.t.r 80g's gross. if i could get my pics on here i would love to show 2 u guys. some day i might get smart enough to do that. again thanks 4 the input. Quote Link to comment https://www.bigmacktrucks.com/topic/32884-mack-gear-ratios/#findComment-208115 Share on other sites More sharing options...
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