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Rob:

What I have I believe is called a "married box", which is to say that the main and auxiliary are bolted together as an integral unit w/o a driveshaft between them.  Both the main and auxiliary have Mack labels, and are clearly meant to be a unit.

Should I look again for the Q?  It's very possible I missed it; these stampings were faint at the best.

Thanks

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I would say your rear end ratio is either 8.15 or 9.02's if you have 11:00 tires.

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It's raining out here, as usual.  Can't mow, and nothing else to do, so tomorrow I'll go out and 

1. check tire size
2. take a pic of shifting legend, which I believe I transplanted from old cab before repaint.  (Got rid of that putrid green color they put in the interior of these trucks originally.)
3. look again for the elusive 'Q'.  It's dark as the inside of a cow under there.
4. take a pic of the whole tranny

i really appreciate the advice and help.  I'm particularly interested in whether this tranny is original.   Don't know a whole lot about this truck, other than the fact that I got it with a bum engine, no bed, and had to reconstruct it from scratch.  

I will say, after all the work I've put into this truck, that Macks are not disposable  commodities--at least the B models, which is all I know.  Everything on this truck was well built, and, if broken,  is very fixable.  I can't say that about most of the stuff I deal with anymore.

Best Regards,

Day Radebaugh

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Rob:

Further details:

1. Tire size 1100-24
2. Pic of shifting legend.  It reads "14-speed quadraplex transmission with main direct in 4th speed"

0606191113b.jpg.323786735ab38c35f9664755d24ef2db.jpg

3. Found what must be the Q, so it reads TRQ 7220
4. Pic of transmission:

0606191120a.thumb.jpg.3f4056318fe399389b85f3fdf717c4a8.jpg

Thanks for your help.

I grew up in Detroit, and watched with fascination the building of the Interstate system.  Particularly intrigued by the "Michigans" which were hauling rock and gravel.  Mostly Autocars then.  My Dad worked at Detroit Diesel, and so did I for awhile.  He was a salesman for Detroit Diesel, and they were experimenting (this was the '50's) with repowering a variety of trucks with Jimmy's.  He would drive home the latest project they were working on.  Still love the sound of a high-revving Jimmy 2-cycle.

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Being a double OD, you lose a few more gears then a Single OD transmission has.  You don't split 5th, since it is OD, thus it is only a 14 spd   Once you get to 4th OD, the last shift is moving the main box to 5th which completes the double OD.

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Yes, that's exactly my understanding of how it should go.  That is, when I get to 4th Direct (which I think you're calling double-OD) I then shift up by going immediately to 5th Direct.

Don't completely understand the nomenclature on the tranny.  I take it that a) the first OD is what is term HI-Split; b) the 2nd OD would then be what is called Direct.  Is this correct?

I should have 5x4=20 speeds.  How do I end up with 14?  I see that I lose 3 in 5th main by not being able to run 5th in LO-LO, LO-SPLIT or HI-SPLIT, so I'm down to 17.   I must lose another 3 speeds somewhere.  Could it be that I can't use the full auxiliary range in 1st main?

Anyway, plenty of gears for what I need, and thanks for the education.

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Correction:

When I get to 4th HI-SPLIT (which I guess you're calling double-OD) then I go directly to 5th HI-SPLIT.  So Direct must be OD, and HI-SPLIT must be double-OD?

Thanks again.

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Don't get all 20 because of ratio overlap or redundancy which is noted by the asterisk.

Here is a chart with the ratios so you can see what you have. 

Mack Quad Ratios.jpg

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Each box has its own overdrive, when you start off in 1st in the main and first in the aux, shift the four in the aux. put the main in second and put the aux.in low split, then direct and then hi split, when splitting the main box you do not use lo-lo in the aux. do this to 4th in the main and the aux. is in hi split. your last shift is fourth in the main and hi split in the aux  to fifth in the main. sounds confusing but just takes some practice.     terry:MackLogo:

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Posted (edited)

Clear as mud LOL!!

In a std single OD transmission, once in 4th/HI, you go to 5th/LO.  Once in 5th/direct you are direct drive.  Then the overdrive is when you shift the compound to OD.

In your transmission, 4th/direct is direct drive.  Then 4th/OD is the "first" overdrive.  The last shift is 5th in the main box, which basically doubles the overdrive ratio.

Edited by Freightrain

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Many thanks for this information.  I believe I get it now:

1. I lose LO-LO across 3, 4 and 5 in the main.  Minus 3 gears, down to 17.
2. 5 LO is useless, since you've been there already with 4 DIRECT.   Down to 16
3. 5 DIRECT redundant to 4 HI.  Down to 15
4. 2 LO-LO gone as well, so down to 14 effective gears.

Conclusion:

1. Forget about LO-LO unless loaded;
2. Unloaded , option 1: 2(LO/DIRECT/HI), 3(LO/DIRECT/HI), 4(LO/DIRECT/HI), then 5 HI--unnecessary, if unloaded
                                     2:2(DIRECT/HI), 3(DIRECT/HI), 4(DIRECT/HI), then 5 HI--also unnecessary, if unloaded
                                     3:1 (HI), 2(HI), 3(HI), 4(HI), then 5 HI--perfectly OK
                                     4. Better yet: 1 (HI), 2(LO/DIRECT/HI), 3 (HI), 4 (HI), then 5 (HI)--a little easier getting going

Opinions?

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Posted (edited)

I would not worry about starting anywhere near 1st gear.   You've got plenty of gear in the back, as that 13:1 first gear, plus 8.x in the back is 104:1 to the tires.   

With my added Spicer box behind my triplex in LO-LO, my lowest gear is 100:1 to the tires.   Believe me, you don't need that to get moving.  I only use that for slow truck races LOL!!


Figure about 3rd gear for getting moving.  Might even get 4th LO??

Edited by Freightrain

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Just keep experimenting.  Unless you really like shifting?  LOL!  I used to play a lot with mine for no reason...then after 10-15 yrs I only use enough gears to get the job done.

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That's good advice, thanks.  It's time to get in the saddle and try out some of these options.  This discussion has been very valuable in one particular way: I've realized that  I've been spending too much time in the lower gears getting going, and maybe even splitting in the higher gears as well.  Going to forget about LO-LO, and get into the higher gear shifting sequence at about 2nd HI or 3 LO, and take it from there.  

The nice thing about this particular quad is that it's so easy to shift the compound, at least after it's warmed up.  

Appreciate the advice.

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Drove it around on the weekend.  I was pretty happy with 2nd Direct, 2nd HI, 3 HI, 4HI, 5 HI.  However, did notice a) had to use clutch on shifts; b) it was a significant jump in these 3-4-5 HI range shifts.  I googled the effective range of the 237 that I have in this truck, and learned you can safely wind it up to 2100, so I believe I'll wind it up a bit more when I try this again.

Also noticed that, when I put brakes on (such as at a stoplight) air pressure leaked out and tank pressure dropped from about 118 max to below 60.  Truck then started sliding backwards, which was heart-stopping, until I kicked in the spring brake and sat and let pressure build again.

Something to fix underneath, I believe.

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1 hour ago, dayradebaugh said:

Drove it around on the weekend.  I was pretty happy with 2nd Direct, 2nd HI, 3 HI, 4HI, 5 HI.  However, did notice a) had to use clutch on shifts; b) it was a significant jump in these 3-4-5 HI range shifts.  I googled the effective range of the 237 that I have in this truck, and learned you can safely wind it up to 2100, so I believe I'll wind it up a bit more when I try this again.

Also noticed that, when I put brakes on (such as at a stoplight) air pressure leaked out and tank pressure dropped from about 118 max to below 60.  Truck then started sliding backwards, which was heart-stopping, until I kicked in the spring brake and sat and let pressure build again.

Something to fix underneath, I believe.

chock the wheels and slide under while somebody touches brakes, could be a multitude of things, from front to rear!!    terry:MackLogo:

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Best thing I liked driving a B was the look people give you when you run through a few gears backing up.  :)

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That's pretty wild.  Going to have to think that one through before trying it.  Maybe clear the area?

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Posted (edited)

Yes, you can run that 237 up to 2100.   Though some I've heard don't seem to pull strong up there.  Mine seems to do fine?

If you want to not use the clutch, remember to ease off the throttle just before you want to shift.  That eases the torque off the gears and will allow you to pull it out of gear.  If you have it pulled tight, you won't be able to shift without the clutch.  You'll feel it want to slide out of gear when you find that sweet spot. Steep hills, likely  not, as you might loose too much speed to catch the next gear.  It's a learning curve.  It took me all summer to get used to shifting my 237 compared to the old 673.  The shifts were much slower, as the motor doesn't drop in rpm as fast.


Shifting in Reverse?  Simple.  Start in LO, get it moving, ease off throttle, slip into Direct.  Run up RPM, ease off and slip into OD.  Works really slick actually.  I do it every time I put mine away as I back up my driveway into the garage.

 

Air leak?  Check air chambers(broken diaphram) or even a line/fitting.

Edited by Freightrain

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On 6/11/2019 at 1:26 PM, dayradebaugh said:

 

Also noticed that, when I put brakes on (such as at a stoplight) air pressure leaked out and tank pressure dropped from about 118 max to below 60.  Truck then started sliding backwards, which was heart-stopping, until I kicked in the spring brake and sat and let pressure build again.

Something to fix underneath, I believe.

If it’s leaking that fast you should be able to easily hear it and locate it with someone else applying the brakes while it’s chocked. 

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Problem with brakes was easy to find.  Apparently aliens came out and removed the line from the quick release valve to the right front brake.  Reinstalled it, everything okey-dokey.

Tried winding up the 237 to close to 2100 to facilitate shifts from 2 HI-3 HI-4 HI-5 HI but I didn't think the engine liked it much.  Sounded like the valves were floating, or what I imagined to be floating valves.  Perhaps more accurate to say that the power in the engine dropped dramatically at about 2000.  In any case, I think the whole sequence worked well from 2 LO-2 DIRECT-2 HI-3 DIRECT-3 HI-4 DIRECT-4 HI-5 HI.  In other words, splitting in 2, 3, & 4 across DIRECT & HI.  

I must say that the truck runs like a champ, although I don't know that I'd care to make my living in it, or drive cross country, but plenty of guys did quite nicely.

The shifts in the compound of course are dead easy without clutch.  To shift both boxes, have to use clutch, as follows.  Upshift is Main box first, compound 2nd.  Downshift is the reverse.

Does this sound reasonable?

Thanks

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Posted (edited)

I've heard some 237 rev better then others.   Guess it's all in the pump setting.  They were meant to run on the governor all day, so you aren't really hurting anything.  On road, mine cruises at 1800 all day.

Shifting is correct.  Once in next higher main gear, blip the throttle and move the compound back to UD.  Downshifting:  Run the compound back down OD, D, UD, then move it back up to OD(left out throttle and let motor drop down enough to get in gear.  Then pull main out and rev up motor and put in next lower gear.  Repeat.


Believe me, after 18 yrs of traveling in mine, it's wearing on me.  Even with all the upgrades, it still beats you to death ESPECIALLY with the roads around here.  Smooth roads, it fine.  Cruises right along.  Few and far between.

Edited by Freightrain

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