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I see that relationship in the ratios but the tags show it as either a 18 or 20 speed box which makes it confusing.  Technically you have 20 combinations, 24 if you count reverse gears.  The factory tag calling both 20 & 18 added to the confusion.  This is all splitting hairs just as much as gears.  Much like my daily driver, which is a 6 speed, I frequently skip gears. 

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This video is a bit different; it's an 8v71 Detroit with a 13 speed.  I just love the way this guy shifts,  and it's because of his use of the throttle--easy on, easy off.  He never mashes it.   This of course is a lot different than your quad, but the throttle technique is the same.  When you get more comfortable with your quad, try finessing the throttle the way this guy does and it'll make for smooth shifting.  

 

 

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On 11/16/2015 at 7:22 AM, Bigdogtrucker said:

I'd say learn basic shifting with the main box first, then start adding splits :twothumbsup:

Can you drive these just by using the main box? im looking at buying one, ive driven trucks but never like this. ive got a bit of an idea, not to confident though.

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Posted (edited)

Steve, It all depends on the load.. Bob tailing or with an empty trailer you can get away with just the main, then slip in a few auxiliary gear changes to keep your speed/ RPM's comfortable. Then after you are used to both boxes then you can play with the progressive splitting especially with a load on the trailer.

Edited by Brocky
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Brocky

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I am looking at one to buy to cart my little grey fergy around to shows, gunna get a small tray made for her, we call em tabletops here in australia. fergy weighs 1 ton. like the picture

2020-05-15_211735.jpg

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On 9/1/2018 at 2:43 AM, Rev.NitroNick said:

Indeed Terry!  Thanks!  Guess I'll be looking for a transmission identification tag/number.

There is a flat section on the left hand side to the rear of the filler pump where the ID number is stamped.

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wow a cool ride that doesnt need anything....bob

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Posted (edited)
6 hours ago, mkmac said:

There is a flat section on the left hand side to the rear of the filler pump where the ID number is stamped.

No tag, it is stamped in the case, you might have to wire brush it to see it.   terry:MackLogo:

Edited by terry

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I covered this in another post, but it might help to hit it again.  The 20-speed is direct in 5th, and only has 1 overdrive gear (Hi-split 5th).  The 18-speed is direct in 4th, so there are 2 available overdrive gears (Hi-split 4th and Hi-split 5th).  You don't typically use Lo-Split 5th and Direct 5th, because they essentially duplicate Direct 4th and Hi-Split 4th.  So, with these 2 gears left out, you get 18 speeds.

Lo-Lo is normally only used to get started or for crawling.  The sequence for using Lo-Lo and then upshifting could vary a little based on which exact gearset the box had.

Regarding split-shifting, if you don't like moving both sticks simultaneously, you can "triple-clutch" it by shifting one box then the other.  I had the best results upshifting whichever box needs to go up first, then downshifting the other.  So, going up through the gears, I would typically upshift the main first (letting the RPM fall in-between) then downshift the compound (raising the RPM in between).  When going down through the gears, I would upshift the compound first (letting the RPM fall in-between) then downshift the main (raising the RPM in between).  Trying to downshift the main first required too much RPM rise.  In other words, if you have enough RPM headroom to downshift the main box a whole step, then why the hell are you worrying about splitting the gear?

Typical "heavy load" sequence on the 18-speed went like this (not using Lo-Lo unless needed):

Lo-split 1st - Direct 1st - Hi-split 1st

Lo-split 2nd - Direct 2nd - Hi-split 2nd

Lo-split 3rd - Direct 3rd - Hi-split 3rd

Lo-split 4th - Direct 4th - Hi-split 4th

Hi-split 5th

This gave 13 nice, progressive steps (sound like a familiar number?)  The 13-speed Triplex was exactly the same pattern.

On the 20-speed version, you would split each gear 3 ways, for a total of 15 steps.  Same with the 15-speed Triplex.

 

Typical "light load" sequence on the 18-speed went like this:

Lo-split 1st

Lo-split 2nd

Lo-split 3rd

Lo-split 4th - Direct 4th - Hi-split 4th

Hi-split 5th

Again, the same pattern works with the 13-speed Triplex.

For the 15-speed Triplex, you could go all the way to 5th in Lo-split, then split-out 5th 3 ways.

 

Of course, depending on road speed and load, it could change.  Sometimes, instead of going from LS 4th to HS 3rd, I would go to Dir 3rd instead.  That is downshifting 2/3 of a gear instead of 1/3.  This let you pick up at a higher RPM, which really helped if the road speed was falling to rapidly.  Otherwise, you might get into HS 3rd, realize the RPM is too low,  and immediately have to drop to Dir 3rd anyway.

 

To be honest, it was not that often that I had to use all the gears 0n the 18-speed.  That light-load sequence worked on most things.  The most common split-shift was when dropping down from LS 4th to either HS 3rd or the aforementioned Dir 3rd "skip".

 

Sorry for the length!  I don't know much about the modern trucks, but I cut my teeth on an 18-speed Quadruplex!

 

 


"Eagles may soar, but weasels don't get sucked into jet engines."

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kind of wierd,,,i broke in on a triplex R model....now my work truck is automatic,,,dont have to touch it at all...just click it in gear like a car.lol.bob

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