Trucking With Bracham - All About Shifting In Point Form

This is everything I can think of about shifting without actually describing how to shift.

Basics:

  • the upshift numbers given here work well for a 13 or 18 speed transmission, with a Volvo, Caterpillar, or Detroit 60 Series engine
  • the downshift numbers given here work well for a 13 or 18 speed transmission, with a Volvo or Caterpillar engine
  • difference in RPM between whole gears is typically 400 RPM with no ground speed change
  • difference in RPM between half gears is typically 200 RPM with no ground speed change

Shifting up:

  • first to second and second to third can typically be made with hardly any RPM increase
  • top RPM for first and second gears should be 1200 and 1300, respectively
  • the above first two shifts should typically be made before starting any turn on a street -- at least shift to second before turning!
  • shifting third to fourth should start at 1400 RPM, and every upshift above that, including splits, should be made at 1500 RPM
  • if RPMs are accidentally increased over the above numbers and a shift is necessary, it should be made immediately
  • if RPMs are below the above numbers at all (for fourth gear and above) and you are NOT on a downslope, DO NOT make an upshift -- increase the RPMs and then shift up
  • upshifts on downhill slopes can be made at slightly lower RPMs, and will be slightly quicker than "normal"
  • when shifting up on downslopes, avoid using splits; they are not necessary to stay in your high torque RPM
  • upshifts on uphill slopes, when they are possible, should be made at the above RPMs or 100 higher, and will be slightly slower than "normal"
  • when splitting up, ensure the RPMs drop enough to engage the higher gear, this may seem to take slightly longer at higher speeds / in higher gears

Shifting down:

  • the goal of every downshift should be to finish it at 1500 RPM
  • making a downshift should not take any longer than a normal upshift, maybe two or three seconds at the most
  • a normal downshift of a whole gear on a firm, flat road surface (with no speed change) should start at 1100 RPM and finish at 1500 RPM
  • a normal downshift of a half gear on a firm, flat road surface (with no speed change) should start at 1300 RPM and finish at 1500 RPM, and be completed within about two, maybe three seconds
  • if RPMs are lower than 1100 RPM when in fifth gear or higher, do NOT attempt to speed up, just make an immediate downshift of a whole gear
  • if RPMs have increased so that a downshift would finish above 1500 RPM, slow back down before starting the downshift
  • when making a downshift on an upslope, avoid splits, as the truck will slow down, likely resulting in no change of RPM (only exception is splitting 5-high to 5-low in a 13-speed, which is necessary to get to low range)
  • downshifts on upslopes should be started at higher RPM than normal, as the truck will slow down while the shift is being made; depending on several factors, the driver may find the next lower gear anywhere from 100 to 400 RPMs above the RPM they started the shift at
  • downshifts on downslopes should be started at lower RPM than normal, and still aim to finish at 1500 RPM, as the truck will speed up while the shift is being made; if the shift is made quickly, the driver may still find the next lower gear only 400 RPMs higher than the RPM at which they started the shift, but if the shift takes too much time the truck may speed up too much for the target gear
  • if ground speed has increased too much while downshifting, the driver will have to do one of two things: either find the previous gear at approximately the same RPMs the lower gear should've been at, or use the brakes to slow down and then find a gear with the accelerator
  • when splitting down, always bring the RPMs up until it is clear that the lower split has engaged, either by an audible engine tone change, or by feeling the engine accelerate the truck at least momentarily

Missed shifts:

  • the most important part of handling missed shifts is accelerator and shifter control
  • when a shift is missed, the accelerator must be used in a very controlled manner to increase or decrease the RPMs as necessary while the shifter is held gently towards the chosen gear to feel (without grinding) if and/or when the RPMs are close to correct, or correct to finish the shift
  • while gently feeling a gear, if the "buzzing" turns to "bumping" and then goes back to "buzzing" while the RPMs are changing in one direction (up OR down), the correct RPM for that gear has been passed -- that slower "bumping" means the RPMs are almost matched for the gear to be engaged

Handling missed upshifts:

  • when an upshift is missed and speed is not dropping quickly, back off the accelerator to reduce RPMs slightly more in a second attempt to catch the missed gear; if the gear is not found on a second attempt, keep RPMs reduced and go back to the gear you started the shift from
  • when an upshift is missed and speed is dropping quickly (uphill, soft surface, trailer not straight behind tractor, etc), keep RPMs reduced and go back for the gear you started the shift from
  • when an upshift is missed and speed is increasing (on a downslope), increase RPMs slightly and find the missed gear

Handling missed downshifts:

  • when a downshift is missed and speed is not dropping quickly, use accelerator to set RPMs back at target RPM or slightly lower, and find the gear
  • when a downshift is missed and speed is dropping quickly, reduce RPMs from where the gear initially should have been (1500 to 1400, 1300 RPM or maybe even lower) and find the gear; if speed is dropping quickly enough, you may have to try the gear below that in the same way, starting with slightly higher RPMs again
  • when a downshift is missed and speed is increasing, quickly increase RPMs above initial target and find the gear; if gear cannot be found before RPMs get too high, reduce RPMs slightly and find next higher gear