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changing rear ratio to get more mph


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if you give me the tire size and transmission model I can get you pretty close to max mph @ whatever rpm, i swapped from 4.64 to 3.65 with an Eaton 9 spd so .73 OD and 11R24.5 tires, I went from wound out at 70 to 1400rpm @ 70. If ypou have an Eaton OD trans and 11 R 24.5 tires a 4.42 will make about 1600 rpm @ 65, 4.17 would do 1500@65mph

"Any Society that would give up a little LIBERTY to gain a little SECURITY will Deserve Neither and LOSE BOTH" -Benjamin Franklin

"If your gonna be STUPID, you gotta be TOUGH"

"You cant always get what you want, but if you try sometimes you get what you need"

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Brandt: It'd be cheaper next time you need tires to get 24.5 rims and buy 11R24.5's for the truck. That'd get you CLOSE to where you want to be for only the cost of the rims (IF you time the upgrade to when you were buying tires anyway...)

When approaching a 4-way stop, the vehicle with the biggest tires has the right of way!
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i have a mack 6 speed with 4.64 runs at 2000 rpm about 65 now what would 4.42 do?

what size tires?, like I said above I can do the math but not withou the tire size and the trans ratio.

"Any Society that would give up a little LIBERTY to gain a little SECURITY will Deserve Neither and LOSE BOTH" -Benjamin Franklin

"If your gonna be STUPID, you gotta be TOUGH"

"You cant always get what you want, but if you try sometimes you get what you need"

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low pro 22.5 are 40" tall, 11R22.5 and low pro 24.5 are 42" tall, 11R24.5 are 44" tall use this and your info in this calculator.

http://www.powerblocktv.com/resources/

"Any Society that would give up a little LIBERTY to gain a little SECURITY will Deserve Neither and LOSE BOTH" -Benjamin Franklin

"If your gonna be STUPID, you gotta be TOUGH"

"You cant always get what you want, but if you try sometimes you get what you need"

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I too am looking at getting more speed out of my superliner since I changed the trans from a 9 sp. to a 12 sp. Does anyone know the high gear ratio on a 1070B? I also have 4.64 with 24.5" tires, looking at going to 4.17 but not sure of final ratio in the 12 sd. Is this trans also .78?

Live every day like it's your last, because one of these days, it will be.

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Puppydog, Going from a 4.64 to a 4.17 would be ok for your overall gearing, youll lose a little torque but little, I doubt you would notice much difference in power from a 4.64 to a 4.17. I have run 4.64, 4.42 and 4.17 oin tri axles running 74,000+ pounds and they all ran fine for me, it really all depends on you, yes a trtxl1070 or 1070B would get you some more speed but even with that you would want to get up to a 4.42 to get the same cruise speed as a 4.17 with your trans. The math with a 1:1 trans and 11R24.5 tires comes out at 2300rpm@65 for a 4.64 and 2070 for 4.17 rears, a .78 OD will get you down to 1790rpm with 4.64 and 1600rpm @ 65mph with 4.17 rears. I would make the swap to a 4.17 if it was me, the 4.64, 4.42 and 4.17 are very common Mack rear ratios so finding a set and swapping your carriers shouldnt be an issue. You will need to know the carrier input splines on the driveline and axle splines, also if it is taper mount or saddle mount on the torque rod on top, taper looks like a drag link end with one big nut, saddle mount has two smaller bolts and a wishbone style bar.

"Any Society that would give up a little LIBERTY to gain a little SECURITY will Deserve Neither and LOSE BOTH" -Benjamin Franklin

"If your gonna be STUPID, you gotta be TOUGH"

"You cant always get what you want, but if you try sometimes you get what you need"

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If swapping, remember that there are two style of mounts for the longitudinal torque rods between the trunion cross member and the carrier.

One has the tie rod taper mount in the top of the carrier with one nut or the style utilizing two bolts to attach to the carrier.

Jim

It doesn't cost anything to pay attention.

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I have 4.17 on my rd and im lookin for 4.64 ...if any on you guys would maybe like to swap let me know..only thing I need is for the rear axle to have or be drilled for a transverse torque rod bracket

Looks like the perfect match here, you want 4.64's and he wants more road speed, dun deal!

"Any Society that would give up a little LIBERTY to gain a little SECURITY will Deserve Neither and LOSE BOTH" -Benjamin Franklin

"If your gonna be STUPID, you gotta be TOUGH"

"You cant always get what you want, but if you try sometimes you get what you need"

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I want too know if I can change just the side gears on my rears to 4.17 from 4.64? I have the manuals and have rebuilt my transmissions, motors, but no rears. Do I need to change anything else? If possible, I think changing the side gears would be a lot easier than the unit.

Live every day like it's your last, because one of these days, it will be.

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I'm too afraid not.

When you talk about side gears do you mean an upper (bewel) gear set?

If yes you need to set the position of the gears to each other to get a correct contact area, also you have to set the bearings pre-load.

A lot of work, I'm going to get over it one day but I have no chances to find ready rears of the kind I need.

Much more easier to swat just diffs. You need to get them out for rebuilt anyway.

Никогда не бывает слишком много грузовиков! leversole 11.2012

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