1wonton Posted May 14, 2019 Share Posted May 14, 2019 How can I determine the rear axle ratio for my B75? ron Quote Link to comment https://www.bigmacktrucks.com/topic/57211-ratio/ Share on other sites More sharing options...
Hobert62 Posted May 14, 2019 Share Posted May 14, 2019 Jack it up, put it in neutral, turn the tire, and count the revolutions of the driveshaft for 1 revolution of the tire. It will get you an idea if you accurately make the yoke and wheel before you start turning. 2 Quote Link to comment https://www.bigmacktrucks.com/topic/57211-ratio/#findComment-422793 Share on other sites More sharing options...
Freightrain Posted May 14, 2019 Share Posted May 14, 2019 Look for the flat on the drivers side of the differential and see if it is stamped? 2 Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/57211-ratio/#findComment-422796 Share on other sites More sharing options...
h67st Posted May 15, 2019 Share Posted May 15, 2019 15 hours ago, Hobert62 said: Jack it up, put it in neutral, turn the tire, and count the revolutions of the driveshaft for 1 revolution of the tire. It will get you an idea if you accurately make the yoke and wheel before you start turning. Make sure the other side stays on the ground or it will spin and throw off your count. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/57211-ratio/#findComment-422825 Share on other sites More sharing options...
Vladislav Posted May 16, 2019 Share Posted May 16, 2019 For the correct count you need wheels at the both sides to turn together. If you have one on the ground (locked from turning) you count must be divided by 2 since the only wheel is forsed to make 2 times more revs by differential. 1 Quote Никогда не бывает слишком много грузовиков! leversole 11.2012 Link to comment https://www.bigmacktrucks.com/topic/57211-ratio/#findComment-422925 Share on other sites More sharing options...
Vladislav Posted May 16, 2019 Share Posted May 16, 2019 Worth to add. The most accurate count of the reatio is count of actual number of the teeth. But complete carrier remove could be required. Talking about Mack tandem carriers you can count the teeth of the upper (bewel) set of gears through the side cover opened but not the lower (bull) ones. Quote Никогда не бывает слишком много грузовиков! leversole 11.2012 Link to comment https://www.bigmacktrucks.com/topic/57211-ratio/#findComment-422926 Share on other sites More sharing options...
h67st Posted May 17, 2019 Share Posted May 17, 2019 5 hours ago, Vladislav said: For the correct count you need wheels at the both sides to turn together. If you have one on the ground (locked from turning) you count must be divided by 2 since the only wheel is forsed to make 2 times more revs by differential. You're right, divide by 2. When I have both wheels off the ground, the opposite wheel usually spins backwards, throwing off the ratio count. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/57211-ratio/#findComment-422949 Share on other sites More sharing options...
1wonton Posted May 20, 2019 Author Share Posted May 20, 2019 Kind of hard to do with two rear axles. I'll chk for the stamp. Quote Link to comment https://www.bigmacktrucks.com/topic/57211-ratio/#findComment-423195 Share on other sites More sharing options...
j hancock Posted May 20, 2019 Share Posted May 20, 2019 4 minutes ago, 1wonton said: Kind of hard to do with two rear axles. I'll chk for the stamp. See the bottom picture for the location of the stamp. Quote JimIt doesn't cost anything to pay attention. Link to comment https://www.bigmacktrucks.com/topic/57211-ratio/#findComment-423197 Share on other sites More sharing options...
1wonton Posted May 21, 2019 Author Share Posted May 21, 2019 Thank you j, this was helpful. I found the numbers are depicted in the tech sheet but it doesn't tell me much. The carrier says CRDP 92.161.66, what does this mean? ron Quote Link to comment https://www.bigmacktrucks.com/topic/57211-ratio/#findComment-423316 Share on other sites More sharing options...
terry Posted May 22, 2019 Share Posted May 22, 2019 1 hour ago, 1wonton said: Thank you j, this was helpful. I found the numbers are depicted in the tech sheet but it doesn't tell me much. The carrier says CRDP 92.161.66, what does this mean? ron It should be right next to the stuff you found, sometimes stamped, or numbers made by a center punch, sometimes real light. terry Quote Link to comment https://www.bigmacktrucks.com/topic/57211-ratio/#findComment-423319 Share on other sites More sharing options...
Vladislav Posted May 22, 2019 Share Posted May 22, 2019 Look more over that square spot on the carrier front. Usually at the right side at the the bottom are numbers indicating the ratio. They're standing apart from the rest. Something like 5.02 or 4.46 or 5.73 etc. 1 Quote Никогда не бывает слишком много грузовиков! leversole 11.2012 Link to comment https://www.bigmacktrucks.com/topic/57211-ratio/#findComment-423348 Share on other sites More sharing options...
1wonton Posted May 22, 2019 Author Share Posted May 22, 2019 Found r 6.34 on real bogie; does this mean the ratio is 6.34? Quote Link to comment https://www.bigmacktrucks.com/topic/57211-ratio/#findComment-423371 Share on other sites More sharing options...
terry Posted May 22, 2019 Share Posted May 22, 2019 1 hour ago, 1wonton said: Found r 6.34 on real bogie; does this mean the ratio is 6.34? I would say yes, for that year of truck. terry 1 Quote Link to comment https://www.bigmacktrucks.com/topic/57211-ratio/#findComment-423375 Share on other sites More sharing options...
1wonton Posted May 22, 2019 Author Share Posted May 22, 2019 OK, thanks gentlemen. I'm about maxed out at 55 and 2000 rpms. Can't keep up with the big boys but I catch them in the mountains. Quote Link to comment https://www.bigmacktrucks.com/topic/57211-ratio/#findComment-423386 Share on other sites More sharing options...
Freightrain Posted May 22, 2019 Share Posted May 22, 2019 Ya, back when power was low, gearing was slow. What transmission? If it is single OD, then 55 is likely about it. My B had 4.62's and would go 65 mph flat out. A double over would get you closer to 65 mph. Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/57211-ratio/#findComment-423390 Share on other sites More sharing options...
1wonton Posted May 23, 2019 Author Share Posted May 23, 2019 OK, thanks gentlemen. I'm about maxed out at 55 and 2000 rpms. Can't keep up with the big boys but I catch them in the mountains. Single od, quadraplex. Emd 673 turbo. Quote Link to comment https://www.bigmacktrucks.com/topic/57211-ratio/#findComment-423498 Share on other sites More sharing options...
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