mack gear ratios?

[superliner237]

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.

[j hancock]

Not that I have heard.

You will also need tire size and know your overdrive ratio to do your calculations.

[Timmyb]

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!

[Timmyb]

Sorry wrong link, try searching "106042 speed chart"

[Timmyb]

Took some screen shots in case you couldn't find it

[j hancock]

If a Mack carrier says it is a 4.17 (for example), it is a 4.17.

[VALS327]

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

[RowdyRebel]

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.

[superliner237]

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.