Choosing a gear for down hill

I usually put on my cowboy hat,shine up my trash can sized belt buckle,adjust my chain driven wallet,lay on my locomotive air horns,kick 'er into neutral,and free wheel down the mountain at 114 mph,all the while yelling into the CB for all those "pansy azzed newbie's" to get out of my way.....LMFAO!!!!! I'm kidding,obviously. A good rule of thumb is to start with whatever gear you ended up in to pull the load UP the mountain,and adjust down from there.IMHO, No such thing as a little too slow.A little too fast is going to have devastating consequences however.

 

When you're driving along, notice the speed at the top end of the gear, where you run out of the power band of the engine....what gear tops out at 25mph, which one tops out at 35, and which tops out at 45. Usually, only the rooster cruisers and the largecar bullhaulers will be geared so high that they can run 55 mph and still have 2-3 gears to go. The majority, at 55 mph will be at the next to the top gear of the transmission, AKA The Big Hole. The signs will tell you the grade of the hill and how long the grade continues. If it's only a mile or two, odds are you won't burn anything up. 3-4 miles, take caution. 5 or more, watch out! 4 %grade, no problem. Stay in the big hole, turn off the cruise control button and set the jake on the highest setting...no need to gear down on even the long grades. 5%, gear down 1-2 gears, depending on the length of the downgrade. 6%, gear down 3-4 gears, depending on the length of the downgrade. This should keep you within the 25-35 mph speeds for the duration of the downgrade. It's slow, yes...but until you know your truck well, it will keep you out of trouble. Usually, on the interstates, you will not see a higher grade than 6%. If you're on a 2 lane and you see a higher grade, shift back to the low side of the transmission.

Once you become comfortable with the truck and know it better, continue to gear down as I told you. The difference being, if the jake slows you down, on the downgrade, up shift 1 gear UNTIL you neither speed up or slow down. THIS IS THE CORRECT GEAR FOR THE DOWNGRADE.

 

Good one Six....hit it right on the head.

 

Don't underestimate Cabbage....It's taken it's share of Steering Wheel Holders in the past....

 

What the heck does the "highest legal speed" have to do with going down grade...?

 

Maybe because some grades have split speed limits....
Like "The Divide" coming down to Silverthorne and coming down to Vail....

 

I'm surprised that students aren't taught how to downshift on downgrades. It's an essential skill. Choosing a gear and jake setting is always an educated guess, because the weight in your trailer and road conditions will always play a factor (and heavy traffic).

Here's my method for safely downshifting on a downgrade (with a shout out to a logging truck driver I met at a T/S counter in 1977 that took the time to explain it to a rookie):

1. AS SOON AS YOU KNOW that you are in a gear too high, then downshift. DON'T WAIT UNTIL THE BRAKES ARE SMOKING.

2. Apply your service brakes smoothly and steadily to bring your speed down until your rpm's are about 700-800.

3. Disengage the jake brake (leaving it engaged can stall the engine during a shift).

4. Tap the clutch to get out of gear, bring the rpm's up to 1200-1300 and float into the next lower gear. NOTE THAT BY STARTING THE SHIFT AT 700-800 YOU ARE ALLOWING EXTRA TIME TO GET THAT GEAR AS DOWNHILL MOMENTUM SPEEDS YOU UP.

5. If you don't get into gear at 1200-1300 increase rpm to "follow" the gear toward 1500-1700 as needed.

6. If you don't successfully get into gear, then apply the service brakes and slow down and repeat getting the gear (you need to know the speed you started to try to engage the gear).

7. Once you have the new lower gear engage, then turn on the Jake Brake again.

8. If the new lower gear can't hold you with the jake engaged, then repeat the process until you find the gear and jake setting that will control your speed down the hill.

 

#1 RULE.....
Pay Attention!!!!....

 

Maybe. What is the relevance with regard to safely making it down the hill?

 

Exactly. Legal speed and safe speed are not the same.

Op, the test answer is one lower than you used to climb the hill. Give them the answer they want to get your license. Once out in the real world, go as slow as you need, never rely on the Jake, it's just one fuse or loose wire from turning off.

Also remember, you can go down that mountain a million times to slow, you will only go down it too fast once.