Double Downs - Downshifting

It was over a decade ago but we were taught to just downshift to the lowest gear in high range but I'm in a different state. Do what the school and state want for the test then develop your own methods.

 

When I got my CDL almost 6 years ago through a community college I was taught "start in 3rd, stop in 6th" as a rule of thumb (10 speed). I used that when I tested (stopping in 6th) and it was not a point deduction in IL. Sure it is different from state to state. I've heard tell that some states will flunk you if you float, where others don't care so long as you are proficient.

As a rule of thumb, most rules of thumb don't work in all situations.

 

I was taking my practice state test on Thursday and they have been enforcing us to try and double down so we understand the concept, I was doing great, letting the tach fall to 800 and then a nice rev, well I guess you can say I got to comfortable with it, I was told to make a left turn at the next light, I had a small grade followed by a small downhill right before the light, I started to slow down and bring the tach to 800 and when I went for 7th I must've hit the range selector without noticing, as I went for 7th it did nothing but grind, I knew if I coasted more than 70' I would fail, so I tried 8th, after 8th started to grind I started to panic and tried 9th and 10th, needless to say I will not double down until I am experienced. After that screw up I came to a stop at the light and realized I was in low range, never did I think to check my selector during that cluster ####. Oh shall I mention that after I realized that I was so pissed at myself for doing something so stupid that I cut my left turn short

 

Let me answer your questions here. First, learn what you need to pass the test. What I'm going to tell you is 'real world' advice. Please excuse the verbose nature of this post, I will try to explain it exactly as I do it on the job.

forget the RPM range!
Forget the RPM range. This will vary between every engine and transmission you drive. Focus on gear to MPH, this will be universal on most straight 10 speed transmissions; focus on engine sound.

UP Shift: Add up the numbers on the tachometer to find your correct gear, using this guide:
15MPH= 6th gear
25=7th gear,
35= 8th gear
45= 9th gear
55= 10th gear

DOWN SHIFTING:(this will assume you are traveling from 55MPH and decreasing speed)
50MPH= 9th gear
40MPH=8th gear
30MPH= 7th gear
20MPH= 6th gear
10MPH= 5th gear (and then you hit the parking lot gears)
Note: In theory, your 9th gear would be at 45 MPH when up-shifting and the top speed for 9th gear is about 50 MPH. So the MPH listed here are for the 'top speed' for each respectable gear. If that makes sense. This example is applicable to most of these gears.

skipping gears; incline

You asked about skipping gears on an incline. Because you are going on an incline, naturally you will loose speed faster. This is especially true when loaded. For the purposes of a road test, you will be empty.

To make sure you don't drop speed too much, continue revving the engine and applying the throttle as you make your way up the incline. But you need to not apply as much force; just gently rev the engine up so you are in control of the deceleration.

So say you are going 35 MPH up to an overpass. You know you'll want to be at 15 MPH at the top of the overpass for safety reasons. Gently rev the engine and continue up the overpass. The force of gravity will naturally cause you to lose speed. When you drop from 35 to say, 20 MPH, you'll skip two gears down.

On an incline, you'd want to push in your clutch and exactly immediately once you are in neutral, STOMP the pedal to the ground and rev it all the way up to the governor. Listen for it; you'll want to hear the engine really rev up to a high pitch. This is important because the incline will make the RPM drop much faster than on flat surface. You'd be going from 8th gear to 6th gear, so as you rev the RPMs up to the max, you will apply gentle pressure on the stick to the 6th gear hole. continue to apply pressure and eventually the hole will 'open up' and you will fall into the correct gear.

skipping gears; decline;

You asked about skipping gears on a decline. When empty, you will generally not pick up enough speed between gears, to significantly affect your MPH. I would shift as normal, like I am on flat ground.

When loaded, it will depend on the length of grade and steepness, but just expect to gain 5MPH every 3 seconds. You absolutely must plan ahead so you do not get stuck in neutral and fly down the grade to your bloody demise.

In general, if you want to skip gears on a decline, you will take your foot off the accelerator and let gravity slow you down as you approach the very top of the hill while making your ascent . at the top of the hill, apply your brakes a little, and match your speed to the gear you will want to be in for the entire length of the grade. Downshift into the appropriate gear. Put your jake brake on high. Flip it on and off to maintain appropriate speed, and never allow yourself to go over the safe speed limit for the downgrade. I like to stay 5 MPH below the speed limit with my jake on high, flipping it on and off to maintain a steady speed.

Hope that helps.

 

Also, if you want to downshift while you are already going down the hill, you need to use your jake brake and service brakes to reach a safe speed, much, much lower than the speed limit. If the speed limit on the downgrade is 55 MPH, and you know how to downshift perfectly and never grind gears, you would slow down to like 40 MPH, and choose your gear accordingly. Do not attempt this until you perfectly master downshifting.

 

I think Moloko's advise to forget about rpm's and focus on speed is the most important thing about skipping gears. However, in my experience every truck will be a tad different regarding speed as it relates to rpm necessary to get it smoothly into gear. It will all depend on how the company (or your owner) sets up the gear ratios.

The thing you need to do when you get assigned your new truck is start paying attention to what speed you are at when you are at given rpm's. You would do well to make a chart and maybe tape it to the dash as a reminder.

A common situation that calls for skipping gears is when you are coming to a stop for a red light and then the light turns green, or when slowing for stopped traffic ahead that then starts moving again. For example, in my current 10 speed truck let's say I'm cruising along at 65 mph in 10th on the freeway, when traffic comes to a stop and I'm on the brakes allowing the rpm's to drop below 1000. Traffic starts to move again as I take it out of gear getting ready to downshift. I glance down at the speedometer and I'm at 25 mph, I know that I can shift to 8th at about 1000 rpm and give it soft throttle to increase speed. If traffic is crawling ahead I'll shift to 7th at about 1500 rpm's to keep slowing down and find a good cruise speed to match traffic.

Again, every truck will be a tad different. Get used to what rpm's in a given gear give you a certain speed and then it will become second nature what gear and rpm you need for making a shift.

 

I'd like to add that sometimes I will wait for speed to match rpm's on a shift. An example might be taking a dirt road to a rig and I'm cruising at 25 mph in 7th on washboard roads, come to a turn, and see a huge pothole or cattle guard just ahead on a steep uphill. I'll take it out of gear, drop to low range, and hold rpm's at about 1200 and allow the steep hill to slow my speed as I pick 2nd, 3rd, or 4th and wait for the speed to match the rpm's so it drops in like butter. This technique is much easier if you are floating gears rather than double clutching.

 

You will want to spend a significant time in school practicing GEAR RECOVERY. Make those lazy pieces of decrepit money-sucking idiots show you how to do this!

This is invaluable. If you ever get stuck coasting in neutral because you missed a shift, quickly add up the tachometer numbers in your head. If you're cruising in 8th gear at 35 mph and you miss your shift to 9th , and suddenly you find yourself cruising at 20 MPH , a new driver might not know where to go and will coast to a stop. What you want to do, is add up the numbers on your tach in the spirit of 15MPH = 6th gear, 25=7th , etc. Match your speed to the appropriate gear understanding that you will be accelerating forward at this point. Stomp on that accelerator and rev up the engine as hard as the tach will go, and gently apply pressure to the corresponding gear hole. it will drop in place as soon as the RPM matches the speed !

I posted a thread on this a year or so ago, take notes! There's a youtube video on this. Master that and the road tester will never even notice if you missed a shift.

 

Doubt your instructors,that's crap. There are times when one will not have time to downshift to the bottom end, and clutch and brake are necessary to stop in control, particularly if you drive a truck without an engine brake, such as the truck I drive. What does matter is how far you travel out of gear, or with the clutch depressed... 90 feet is what we were taught and examined. BTW, my instructors were state certified examiners. Now, if you forget to change from high to low and stall when taking off from a stop, then that is FAIL.

Also, I was taught how to double down soon. The way I was taught, and practice, is to brake until you feel the engine against the gear, basically 100 RPM above idle, give it 500RPM and shift. Not having an engine brake I do it all the time, and I have a local gig. BTW, I drive 13 and 18spd regularly, 10spd but once.