Triplex shifting

[skydawg]

When shifting from 3`rd to fourth gear,my tranny will not go into 4`th gear until the revs drop below 1000 rpms.I`m never pulling anything but if I was, wouldn`t that be lugging,and not good for the engine?This is a double overdrive transmission w/ a 5.78 rear ratio.

[67RModel]

Someone with experience driving one can chime in but I think what you’re noticing is correct. Once you catch 4th like that you would immediately shift the auxiliary from hi spilt to low split which would bring you back to about 200-250 rpm lower than where you were before (3rd main, auxiliary hi split) you shifted into 4th…if you were loaded. 

Edited yesterday at 01:19 AM by 67RModel

[skydawg]

Ok,I`ll try that,thanks.Haven`t done a lot of splitting yet.

[67RModel]

9 hours ago, skydawg said:

Ok,I`ll try that,thanks.Haven`t done a lot of splitting yet.

It will probably take some practice as it is somewhat counterintuitive. If your in say, 3rd hi split and want the next incremental gear (4th low split), you would, like you said, take the main out of third and let the rpms fall way down to get it into 4th. Then, immediately take the auxiliary out of high split and bring the engine rpms way back up to just under where you were before you shifted the main, and put the auxiliary into low split. Then the next would be a small, "normal" shift of the auxiliary to direct. Then again, a small, "normal" shift of the auxiliary to high split. Then it starts all over again my shifting the main from 4th with a big rpm fall to 5th then immediately following with a shift of the auxiliary, with a big rev match, from high split back to low split. I was always told to never shift both levers at the same time when learning, which is why there is a huge rpm gap when shifting just the main to the next higher gear but I have seen videos of old timers shifting them both at the same time and seemingly never missing a gear. It looks very laborsome shifting both at the same time as one hand pretty much has to be through the steering wheel with your wrist steadying the steering wheel and one palm on each lever. I'm sure it became second nature back in the day to the drivers who drove these things daily fully loaded. As an antique bobtail or hobby truck I think its easiest to leave the auxiliary in direct and shift the main as a normal 5 speed and then when you get to 5th if your on the open road and want top speed you can move the auxiliary to high split for cruising. Below is a good video of a guy shifting one, one lever at a time as I described. I believe he starts out with the main in 2nd as he is just bobtailing......

 

[70mackMB]

Another example.    .....Hippy

 

[Brocky]

That is an excellent video.. You can see how long it takes for the RPM's to drop when shifting the main. Then he brings them back up with the auxiliary. You notice that the RPM drop in the auxiliary is small enough to be able to float shift it. It would be best to hook to an empty trailer, for a little load, in a big parking lot (2nd to 3rd) or a back road (3rd to 4th) to get the hang of how the gears compound themselves. 4th to 5th will be the same BUT you will need room enough for that speed. Not sure on splitting all of 5th as it will depend on your RPM drop going into 5th in the main??? The gear ratios vary for different models of transmissions. Quite possibly you will only need direct and over in 5th??? Notice that in the second video that he shifts both levers at once in the lower gears but does not from 4th to 5th. Just play with it!!! And you will get the hang of it...

[Mark T]

If it's a double over, wouldn't it need to have the compound in overdrive before the main goes in fifth, and forth to fifth in a double over would be a lot less RPM difference than first through forth. (almost like a split in the compound)  In reality, 3rd over to fourth under is probably a tiny downshift.  Might try third over to fourth direct ?   😳  This is going off forty year old memories, so I might be a little off. 

[mowerman]

Pretty normal if you’re not going to split, it’s like shifting a maxidyne great responses fellas but now he’s probably confused. If You don’t have any weight. It’s hard to split anything. You’re just beating yourself to death. Anyway 

[Joey Mack]

I sure wish I knew how to do what pappy is doing. 

[67RModel]

10 minutes ago, Mark T said:

If it's a double over, wouldn't it need to have the compound in overdrive before the main goes in fifth, and forth to fifth in a double over would be a lot less RPM difference than first through forth. (almost like a split in the compound)  In reality, 3rd over to fourth under is probably a tiny downshift.  Might try third over to fourth direct ?   😳  This is going off forty year old memories, so I might be a little off. 

Yes I think so. If its a double over (TRT-720) then the main is direct in 4th and 5th main is a real small overdrive. Below is the ratios for a TRT-72 non overdrive triplex with the 5th main direct. The only OD is 5th high split because high split in the auxiliary is 0.85:1.

[mowerman]

9 minutes ago, Joey Mack said:

I sure wish I knew how to do what pappy is doing. 

I’d like to have his truck lol

[67RModel]

Here is the ratio difference between a direct and overdrive triplex.

[skydawg]

So there`s no point in ever using 5`th low or direct,right?5`th low is lower than 4`th Hi and 5`th direct is virtually the same as 4`th Hi.

[mechohaulic]

3 minutes ago, skydawg said:

So there`s no point in ever using 5`th low or direct,right?5`th low is lower than 4`th Hi and 5`th direct is virtually the same as 4`th Hi.

memory correct; that's the difference between a quad 20 speed and quad 18 speed . dash shift pattern states not to use those two combos. 

[mowerman]

Yes, normally there’s one or two gears you skip I believe even duplex from what I remember you go from fourth high to fifth high

[mechohaulic]

47 minutes ago, Joey Mack said:

I sure wish I knew how to do what pappy is doing. 

at least Pappy was smart enough NOT to put his arm through the steering wheel when twin shifting.  hit a bump/pothole and that wheel can move quickly with force causing a sore arm -(so I've heard )LOL Bulldog had  a winter coat similar to one on my '77 F-350. watching dash gauges RPM's didn't move much =neither did the left foot from drivers in both videos while shifting. I don't remember the B61 I drove part time as a fill in having the lady's voice telling me when to turn as with the green Mack.

[67RModel]

19 minutes ago, skydawg said:

So there`s no point in ever using 5`th low or direct,right?5`th low is lower than 4`th Hi and 5`th direct is virtually the same as 4`th Hi.

I wouldn't say that. They just aren't progressive shifts from the next lower sequence of gears. There may be a time when you would be in 5th high cruising and come up on a scenario where you need to grab a slightly lower cog so you could move the auxiliary to direct or low split and then go from there. I think its just a preference if you want to change the main gear to 4th or the auxiliary to direct. But yes going up through the gears in a progressive manner those two are redundant.

Edited yesterday at 02:24 PM by 67RModel

[67RModel]

[mechohaulic]

20 minutes ago, skydawg said:

So there`s no point in ever using 5`th low or direct,right?5`th low is lower than 4`th Hi and 5`th direct is virtually the same as 4`th Hi.

every time you turn the key and let the clutch out will be a learning experience. in due time a driver becomes one with the truck. a book will show normal shift sequence ; many variable determine actual pattern == load size/ terrain/ weather conditions etc. a driver will learn when to shift not always by what the gauge shows but how the engine sounds. times will call for skipping two or more gears whether from main or aux, it's a learning practice. hopefully it will be a fun one also.

[davehummell]

I have a triplex in my B model and it is a double over when I shift from third high to fourth I drop back to direct and when the speed and rpm is right I shift into overdrive on the hot stick when I want to keep up and pass others on the highway I pull it back into 5 over the 373 rear gives me quite the road speed. My trans usually will grind a little bit going into fourth especially if I let the rpms up over 1800

[mechohaulic]

only time I ever got to notice differences in "over/ double over transmission ratios was when repairing  a two stick duplex . was from a cab over F model which driver missed a shift going up steep hill pulling load of water. shattered the back half and of course the truck had to be running next day, owner  located(stole) a 10 speed from a contractor near by. while bosses/wife's went to a party left me in garage using a john deere backhoe for crane removed broken 10 speed = swapped back halves -reinstalled transmission which took till am next morning ,left there went right to full time job, only to hear from driver "it doesn't shift right . big difference in ratios" well next time steal a different Transmisson .

[67RModel]

4 minutes ago, mechohaulic said:

only to hear from driver "it doesn't shift right . big difference in ratios" well next time steal a different Transmisson .

Yea he should have stollen the correct duplex 🤣. However, he was not wrong. If you look at the ratios between a direct and over gear triplex the difference is not insignificant at all. If your truck had rears geared for one, then swapping to the opposite transmission would readily apparent.

[Mark T]

1 hour ago, skydawg said:

So there`s no point in ever using 5`th low or direct,right?5`th low is lower than 4`th Hi and 5`th direct is virtually the same as 4`th Hi.

You're not supposed to use any combination other than compound in OD and main in 5th with a double over.  It'll go in them, but you're not supposed to use them.  IDK  might work better for you to try 3rd direct to 4th direct then move the compound to under ???   First second and third are usually easy pezzy....after that, you need to get familiar with the truck.

[skydawg]

Ok,thanks everyone...I`ll experiment.

[terry]

3 hours ago, skydawg said:

So there`s no point in ever using 5`th low or direct,right?5`th low is lower than 4`th Hi and 5`th direct is virtually the same as 4`th Hi.

If it is a double over transmission, you go 4th hi split to 5 th high split, no splits in fifth gear.  terry