Jake breaks in the rain

to drive in ice, every reaction has to be slow, calm and collected. My idea of slippery was rain, that's what the op asked. Ice? That's a different thing all together!

 

i think any truck with traction control will most likely kill the brake and/or cruise if either are in use and a loss of traction occurs. the mack i drive is quicker at such than any human could be.

i use the engine brake pretty much all the time. it has a high and low setting. low is only good if you're basically empty or on soft hills. anything over that needs high to be effective. improper use can most definitely cause a jack knife.

 

Excellent question.

I use Jakes frequently on snow, ice, and muddy roads. Here's the correct way to use them without jacknifing:

Step 1 - I don't normally drive with the Jakes on, like some drivers do. When I want to engage the Jakes in slick conditions I select the lowest setting. Some trucks have only two settings, high and low, others have three settings, low, medium, and high. Select the lowest possible setting.

Step 2 - the Jakes have the most holding power above 1500 rpm's with maximum holding power at around 1800-2000 rpm's. I want to engage the Jakes in the lowest setting at around 1200 rpm's and let the rpm's climb (if I am descending a grade) AND I will play with the Jake setting, bringing it up to medium or high.

At all times during this maneuver I am on high alert for any tendency of the trailer to come around or for any skidding of the drives. If that happens I will drop the Jake setting to low and/or cancel the Jake by turning off the Jake switch or SLIGHTLY getting on the throttle. If I cancel on a downgrade the preferred method is to turn off the Jake switch and get LIGHTLY on the service brakes to bring speed down to around 800 rpm's, then downshift to the next lowest gear around 1200 rpm's, then try to reapply Jakes in the lowest setting.

Sometimes you will be in the #### coming down a mountain grade when chains aren't required, when chaining up would have been a far better option. Mountains make their own weather. A typical example is the climb up and through the Eisenhower Tunnel on I-70 in Colorado. It can be sunny, with bone dry roads down below, but you can drive into a blizzard up there. Being able to use Jakes on a multi mile descent will help you maintain a safe speed.

 

Snoqualmie is another example.

 

Thats why i like the new trucks.....the engine brake on the new trucks arent as load as the older jake break trucks...so i ignore every sign that says no engine brake permitted

 

Using your jake brake in the rain or even on the snow is not likely to cause a jackknife because it only slows down the front drive axle. The rear one is just coasting and helps to maintain your line. That is, as long as you don't have the interaxle differential locked in.

 

Definitely with all the new abs...anti what the hell ever and stability ######## on the new trucks...back in the day i could see it happening

 

I'm not sure I agree with your post.

Thank you for mentioning engaging the IAD aka "Power Divider". I ALWAYS have this engaged in slick conditions. Getting off road on dirt or mud roads I engage it as a matter of habit and disengage it once I am back on dry pavement.

The power divider lets both drive axles apply power instead of only one. It also works when applying Jakes, so it SHOULD be engaged in slick conditions.

Regarding your statement that applying Jakes won't cause a jacknife because the trailer continues to roll freely is wrong IMHO. When you apply the Jakes the trailer will want to continue to push forward into the kingpin. That push is what can cause a jacknife. This is why applying the trolley brake can be helpful to take pressure off the kingpin. However, many modern trucks have trolley brakes that were designed by blithering idiots. Don't use the trolley brake if you can't apply less than 10 lbs psi, many are designed to immediately apply 20 lbs or more.

 

The rears operated the same exact way back in the day too. As long as the interaxle differential is not locked in, the only thing that will happen is that the drive tires on the front axle may stop turning. I guess in an older truck, that might cause the engine to stall which would be a bad deal.

 

We will have to agree to disagree. I don't want both axles under power in slick conditions because just letting off the throttle too hard can cause the rear to come out from under you... the same as a car with a manual transmission and a Positrac rear end would if you did the same. Having one axle just along for the ride is much safer on the slick stuff.

The only time mine ever gets locked in is on uneven terrain where one wheel on the front drive gets lifted off the ground and won't bite.