J-Brake Question

If you are using the clutch when you shift the jake will be deactivated. There's no real need to have the jake on unless you are going down a hill. Using it for primary braking puts additional wear on the tires on the drive axle wearing them out needlessly. Learn to plan ahead in your driving, back off the throttle well before your exit and let the truck slow down naturally. Anytime you use the brakes, or jake brake, you are wasting fuel.

There are different setups for the various truck and engine manufacturers. The Jacobs Engine Brake (a.k.a. Jake Brake) is just one model but the name is nearly universally applied to all engine brakes. Various options are On-Off, Off-Low-High (3 or 6 cylinders contribute to braking), Off-1-2-3 (2, 4, or all 6 cylinders contribute to braking).

Engine braking should not be used on slippery roads (rain, snow, ice), the braking action is applied to only one axle and can easily cause loss of control and jack knfe, it happens all the time.

 

That was a GOOD question.

Not stupid at all. Others were too embarassed to ask !!!!

 

Well, look at it this way, if you learn to shift properly with the clutch you are technically "doing it the right way." Learn and master that first.

Transmission manufacturers will tell you it's alright to float the gears as long as you do it properly. Mastering using the clutch (i.e. double clutch) will still make you learn proper throttle control so you know how much to rev the motor or let it drop depending which way you go through the gears. When you have that down it is easy to shift without the clutch.

Where the jake comes into play is that when you use the clutch, a switch disengages the jake as you depress the clutch pedal. If you don't use the clutch the jake is still on, and when you back off the throttle the least amount it will 'bark' at you and the rpms drop in an uncontrolled manner. You also can put quite a strain on the trans by having it slide into gear as the rpms drop that rapdidly. Again, there's no real purpose to making all that racket while shifting except for the 'look at me I drive a big truck' factor as people look to see what the racket it.

The purpose of the jake is to allow a controlled descent on a grade, allowing you to maintain a reasonably steady speed without having to ride your brakes. They will be there if you need them as long as you haven't heated them up. Having the jake on all the time has no purpose, and if used for routine slowing and stopping then the truck is not being driven in the most fuel efficient manner. In an emergency stop it is possible to lock up that one drive axle with the combined stopping power of the normal service brakes and the jake, although ABS has reduced much of that problem. ABS does NOT exert any influence over the engine brakes though, which is why using it on slippery roads can still result in locking up the axle. I've spoken with many drivers who have it backwards, they think they should just use the jake in ice and snow and stay off the service brakes. It's the opposite, a little bit of brake applied to all five axles slows the whole vehicle as a unit. Using just the jake only slows the tractor, so if the trailer is not absolutely perfectly in-line with the tractor it will try to continue on at the same speed as before as the tractor slows down. Result - jack knife.

Hope that helps.

Never a dumb question, as they say. If you're not sure it's safer to ask than to find out the hard way. These days there are too many consequences for the old school way of learning. You can be embarassed all you want by being the guy going down the mountain 10-20 mph slower than everyone else, but in complete control and, as they say during flight training, "with the outcome of the manuever never seriously in doubt." Or you can be cool with your jake screaming at 2500 rpm and brakes smoking while you pass all the "get off the road if you don't know how to drive" truckers.

There's a reason they put those emergency run off ramps on the mountain roads, guess which type of driver gets to use them?

 

what he said. As others have said, plan ahead when you can. It makes everything go alot better. When making the down shift, do it soon enough so you can take your time. It is timing. Dont force, slam, or "strongarm" the shifter. Practice will make perfect.

 

I beg to differ. I'll use the engine brake on low when it's slick out. It allows me to not use the service brakes to slow the truck, therefor no chance of tires losing traction, or locking up.

What gets people in trouble with engine brakes and slick surfaces are keeping the bugger on high. That's what gets 'em.

 

Can't agree with you on that at all. To say there is NO CHANCE of your tires losing traction or brakes locking up is a pretty strong statement. NO means never, not physically possible, can't happen. A blanket statement covering all possible load conditions from bobtail to hauling triple trailers, unloaded to gross weight.

If your brakes are adjusted properly, which of course they are because you checked them, then a gentle application of braking to ALL wheel positions will allow a much lower braking force per wheel to be applied to achieve the same amount of speed reduction achieved by using an engine brake alone. Also you are in complete control of the amount of braking force. Engine brake is not controllable except for two or three individual levels. Engine brakes are capable of producing hundreds of horsepower in braking force roughly equivalent to the HP rating of the engine itself, so even divided by three at the lowest level it can be easy to break traction. Also tell me how you can apply an engine brake gently, and apply more or less pressure as needed as you begin to slow? Also you lose braking as speed is reduced and rpms drop.

While many drivers get away with this and never have anything bad happen, many others have soiled their shorts from the unintended consequences. This is the type of thing a "trainer" should be teaching students, but we all know the qualifications to be a trainer at almost every company.

Any truck should be driven in a manner that does not require engine braking, if you count on it being there and it's not you can get in over your head very quickly. There is a point at which a truck has too much weight and speed for it's service brakes to slow or stop it on many grades. Counting on an engine brake to keep you out of that situation is not a good plan.

Whether on a grade or on slick roads basic principles of physics (coefficient of friction and related functions) will win out every time.

 

######......... it comes down to common sense..... If the engine brake is sliding the tires, turn it off......

 

I use my Jake's all the time. It doesn't cause excessive fuel usage, or excessive wear on the engine if used properly.

Anyone whos ever owned a truck without jakes and then owned one with jakes will tell you how much they love them and how much longer their brakes lasted.