How to shift a 5 and 4

Discussion in 'Questions From New Drivers' started by slim66, Oct 18, 2008.

  1. 6aa

    6aa Bobtail Member

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    Apr 25, 2011
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    Out of curiosity, what is the issue with having both in neutral at the same time?
     
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  3. Boardhauler

    Boardhauler Road Train Member

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    Is the brownie fully progressive or does it have a deep under? Makes a difference.
     
  4. heyns57

    heyns57 Road Train Member

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    To mesh the gears, the driver must match the speed of the input shaft with the speed of the output shaft, in each transmission. He controls the engine speed to the first transmission. The output shaft of the second transmission is controlled by the drive shaft. If the second transmission is in neutral, it will not drive the output shaft of the first transmission. If the main box is in neutral, it will not drive the input shaft of the auxiliary. An experienced driver can shift both boxes through neutral almost simultaneously, relying on the momentum of the spinning shafts to find the mesh point. If he misses both shifts on the first attempt, he will be stuck in double nothin'.
     
  5. GasHauler

    GasHauler Master FMCSA Interpreter

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    I was always taught to shift the main first and it's worked for me. One thing about these tranny's is they are tough. I believe that is why the Navy Seabee's kept them around up to the late 80's.
     
  6. heyns57

    heyns57 Road Train Member

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    The box to be up-shifted should be shifted first. An up-shift requires a drop in rpm, and you can drop to idle rpm if necessary.

    If the other box is to be downshifted, you need to increase rpm to that box. Having up-shifted the other box first, you now have more shaft speed to send to the downshift box.
     
  7. paulll

    paulll Bobtail Member

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    drove one in ft mcmurry at the tar sands in 79,pulled a float to move it,strong,had a d-10 on the float,didn t have a clue how the tranny worked,was a mechanic!had to move the bugger,found 2 shifters?used it like a shifter now
     
  8. Prairie Boy

    Prairie Boy Road Train Member

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    I've had a few 5 X 4 and a winch tractor with a 6 X 4.
    Driven Macks with 5 X 3 Spicer 4 X 4. Look on youtube and you'll find videos of 2 stick shifting.
     
  9. Wargames

    Wargames Captain Crusty

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    Jump up in the truck and learn, thats what we did back in the early 70`s.
     
  10. speculator59

    speculator59 Bobtail Member

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    Oct 22, 2012
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    so many wrong answers on this subject. First, one post listed a SST 20 speed spicer as an air shift 5X4. A 5x4 is two transmissions. A 5 speed main with a 4 speed aux seperated be a drive shaft. A SST 20 speed is a 5 speed main box with a 4 speed aux section attached to the back much like a 13 speed roadranger is a 5 speed main with a 3 speed aux or a 10 speed roadranger is a 5 speed main with a 2 speed aux attached. I may be wrong on this. If any one thinks I am let me know. I have several spicer manuals and I will look and see if I have one for a SST 20 but I think I am right on this.

    On the 4x4, it is two boxes but they are bolted together and they set them up with 2 sticks or air shift on the aux (rear box). You only used 3 gears on the aux to each main shift with the exception of starting out in 1st and 1st. Start in first on the main and 1st on the aux then shift the aux to 2nd, 3rd, then 4th. Then slip the main into neutral and pause a bit then slip the aux into neutral at the same time as puting the main into 2nd, then rev the motor(no clutch) back up to 1600 or so rpm (easy, dont tromp it to the floor and hit the governor) and put the aux into 2nd. Next shift is aux to 3rd then 4th and you repeat the process as above to go to 3rd on the main and 2nd on the aux. If downshifting from 4th and 4th you would shift the aux into neutral and raise the rpm's aprox 300 above where you were at and slip the aux into 3rd. Repeat untill you are in 4th on the main and 2nd on the aux. The next shift will be to shift the aux into neutral and pause for an instance. Then shift the aux into 4th at the same time as sliping the main into neutral then raise the rpm back up to aprox 300 above where you were before starting the shift and slip the main into 3rd. You can then drop the aux to 3rd and 2nd before having to split shift again. Just remember, easy on the throttle when raising rpm to sync the gears. If you try to use all 4 on the aux you end up putting it back into a gear with the almost same ratio you came out of. ( 3rd on the main and 4th on the aux is almost the same as 4th on the main and 1st on the aux so you shift without gaining anything)

    The 5x4 I have not driven but I do have a 7X4. Not factory. Came out with a 5x4 but the prior owner put an inexperianced driver in it and tore 3rd gear out of the main. I got the orginal 5 speed but have not repaired it yet. With the 7x4 it is shifted much like the 4x4 except on a hard pull you only use 2 gears on the aux with each shift of the main. The 7 speed has close enough ratios that most of the time I start out with the main in 2nd and the aux in 1st. I can shift the main into 3rd, 4th and 5th then take the aux to 2nd and 3rd. Next I will take the main into 6th and the aux into 2nd then 3rd. Then split shift again taking the main into 7th and the aux into 2nd. Then 3rd and 4th on the aux. If starting out on a hill with a load you can also split the 2nd, 3rd, and4th gears on the main also but only using any 2 gears on the aux. You dont have to use the 2nd and 3rd you can also use 1st and 2nd or use 3rd and 4th but I try to not use the 4th on a hard pull in the lower gears of the main because 4th is overdrive and it is harder on the aux to apply a lot of torque to the overdrive gear. On my 7x4 when shifting and spliting the main with any two on the aux. there is only about a 250 rpm split between gears.

    Once you get onto shifting if you do slip up and get both into neutral all you have to do is push the clutch all the was to the floor to apply the clutch brake and put the main back into the right gear. Which one is the right gear depends on which one you came out of and whether you are going uphill loosing speed or going down hill gaining speed. It has to be the gear that you would have it in for the speed you are going. Then let off the clutch and place the rpm at the proper speed and slip the aux into the gear for the speed you are going.

    There is also transmissions used in lighter duty that are completely different. A lot of chevys with the 366 and 427 gas motors and fords with gas engines and all trucks with small diesels ( 6v53 detroit and such) had 5x4 setups that were complety different that the heavy duty ones. The 5 speeds all were syncrinized transmissions and had to be shifted with the clutch and the aux were what they called "brownie" transmissions were non syncrinized and they could be shifted without the clutch. Been a long time (1980) since I was around them so I dont remember the exact shift pattern on them but with the wide rpm range on a gas engine you could vary the pattern a lot. This post has gotten way too long so going to end now.
     
    heyns57 Thanks this.
  11. speculator59

    speculator59 Bobtail Member

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    Oct 22, 2012
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    getting them back in gear without stopping or ending up with all the gear teeth in the bottom of the tranny. If you have a working clutch brake and know how to do it, it isnt a problem at all.
     
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