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14sp Vs 18sp Quadraplex

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I have seen Mack shifting plates for Quadraplex transmission, in B model cabs, that have both 14 speed and 18 speed. Is there a difference in the transmission? Does anyone have a complete list of the Quadraplex gear ratios?

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Great, I found it on the old site under "Info" or else "Links" and then B "Model Info". Very interesting. Tom Gannaway did a great job collecting that list.

It looks like lo-lo is only usable in 1st and 2nd in the 72 series transmissions. The TRQ-72 looks like a direct main box with 15 speeds and two low holes.

The TRQ-720/7210/7220 all look like a 13 speed double over with 2 "useable" low holes.

I still can't work out the math for 14 and 18, but there must be some logic behind it.

Thanks for the help.


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The 18 speed goes from 4-Hi to 5-Hi (double overdrive)

There are only about 12-13 useful gears buy the time you skip one or two here and there.

The math doesn't add up but the old 'B' will get-R-none.















That's 14 gears and that's makeing every shift.

Skip 1direct and you got 13.

That'a about all you need.

Course differant conditions may dictate something a little differant.

Empty and bob-tail you can skip a couple more.


Keep a clutchin'

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  • 5 months later...

I too was playing around with gears and ratios. Here is all I could really get out of a TRQ-7220 quadbox.

15 5HS 0.70

14 4HS 0.84

13 4D 1.00

12 4LS 1.20

11 3HS 1.47

10 3D 1.76

9 3LS 2.10

8 2HS 2.61

7 2D 3.13

6 2LS 3.74

5 1HS 4.55

4 1D 5.45

3 1LS 6.52

2 2LL 7.92

1 1LL 13.80

Edited by JD 5020
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