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Originally Posted by Windwalker
Originally Posted by wimpy
Ahh, thanks splitshifter, I never realized you could do that, unfortunately I dont have a CAT engine I drive a Volvo with the Detroit engine dont know if it does that, but I'll give it a try thanks for the info, I'm glad to hear I'm not hurting anything in the engine doing that. I dont know what got me thinking about it one day and so I said better get on CAD and ask huh?
By not using the jake when going down a grade, or even using the jake, but in too high a gear so that you must use the foot brake on your way down, you could be setting yourself up for disaster at or shortly after the bottom when that brake suddenly becomes important. You can tell the true professional driver on the way down a grade. If you watch, he/she may be going slower, but the brake lights very seldom, if ever come on. The gear is selected so that the engine braking torque is about equal to the pull of gravity, and the engine controls the speed all the way down. That is the theory behind the design of the engine brake. So, by using it, no, you will not do any harm to anything inside the engine. However, if you use the foot brake instead, you do stand a chance of having cracked brake drums on any one or several of the wheels. And, that becomes dangerous even when you are not going down a grade. I've seen pieces of brake drum on the shoulder of the road after getting to the bottom of Monteagle, TN, on the eastboung side. And, I really don't have to wonder what made the brake drum come apart. When you have the Jake brake dashboard switch on, and the cruise control on/off switch on, the Jake will not come on until the foot brake (or trailer brake hand valve) is applied. Once the brakes are "tapped" slightly,even after the brakes are released the Jake will remain on until either the throttle is depressed, the clutch is depressed, or the dashboard switch is turned off. The Cat powered trucks at work are set up that way. As I said earlier, it makes things easier, because you can leave the Jake dashboard switch on all the time, and not have to worry about the Jake coming on and messing up a shift. |
Splitshifter said:
As I said earlier, it makes things easier, because you can leave the Jake dashboard switch on all the time, and not have to worry about the Jake coming on and messing up a shift. How are you "floating" the gears in your senario without the jakes activating through each shift? The way Im reading it, the cc is not controlling your throttle. (Im not doubting you just not following your scenerio) I have a CAT C-15 in an 07 Classic. I understand the concept of using the Jake brake (jb) and the cruise control (cc). When my cc on/off switch is on and jb switches on, and Im controlling the throttle the jakes will come on if I back completely off the throttle. When I "float" the gears I must not back completely off the throttle or hold slight pressure on the freeplay of the clutch to prevent the jakes from coming on through each shift. If the cc is on and I have the cc speed set to control the throttle, the jakes are basically inactive unless I tap the clutch or brake pedal to deactivate the cc, and Ive never tried to shift while the cc was controlling the throttle. |
The engine brake has an on/off switch??? When did they start adding this???
As far as the engine brake coming on when shifting, all you have to do is barely touch the clutch to disable it. You don't have to push the clutch in, just give it a slight touch and it'll turn off the engine brake. Also, it depends on how the engine brake is configured in the trucks computer as to whether it comes on as soon as you release the throttle or if you have to press the brake pedal first. I've ran trucks that were setup both ways. |
I taught myself to "float" the gears with the jake on and not using the clutch to disable it. All you have to do is just a keep a very light pressure on the gas while not enough to accelerate but just enough to not let the jakes turn on. Works for me.
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Originally Posted by Splitshifter
Originally Posted by Windwalker
Originally Posted by wimpy
Ahh, thanks splitshifter, I never realized you could do that, unfortunately I dont have a CAT engine I drive a Volvo with the Detroit engine dont know if it does that, but I'll give it a try thanks for the info, I'm glad to hear I'm not hurting anything in the engine doing that. I dont know what got me thinking about it one day and so I said better get on CAD and ask huh?
By not using the jake when going down a grade, or even using the jake, but in too high a gear so that you must use the foot brake on your way down, you could be setting yourself up for disaster at or shortly after the bottom when that brake suddenly becomes important. You can tell the true professional driver on the way down a grade. If you watch, he/she may be going slower, but the brake lights very seldom, if ever come on. The gear is selected so that the engine braking torque is about equal to the pull of gravity, and the engine controls the speed all the way down. That is the theory behind the design of the engine brake. So, by using it, no, you will not do any harm to anything inside the engine. However, if you use the foot brake instead, you do stand a chance of having cracked brake drums on any one or several of the wheels. And, that becomes dangerous even when you are not going down a grade. I've seen pieces of brake drum on the shoulder of the road after getting to the bottom of Monteagle, TN, on the eastboung side. And, I really don't have to wonder what made the brake drum come apart. When you have the Jake brake dashboard switch on, and the cruise control on/off switch on, the Jake will not come on until the foot brake (or trailer brake hand valve) is applied. Once the brakes are "tapped" slightly,even after the brakes are released the Jake will remain on until either the throttle is depressed, the clutch is depressed, or the dashboard switch is turned off. The Cat powered trucks at work are set up that way. As I said earlier, it makes things easier, because you can leave the Jake dashboard switch on all the time, and not have to worry about the Jake coming on and messing up a shift. |
IL"m afraid I've driven more than one CAT that did have the jake come on when the cruise was on. It depends on how the software in the ECM is set up. But it does work out nicely because you don't have to "barely touch the clutch" or "keep a light pressure on the throttle" to keep the Jake off while shifting. And when you do want the Jake, a light tap on the foot brake will activate it and the Jake will then stay on until either the throttle is depressed, the clutch is depressed or the dashboard switch is turned off. It's not my intent to start an argument about this, but just to throw a hint out there about the way it works with our Cat engines. I also heard this type of ECM programming referred to as "latch mode" somewhere. |
Drew 10 said
OK...Im not following this. How are you "floating" the gears in your senario without the jakes activating through each shift? The way Im reading it, the cc is not controlling your throttle. (Im not doubting you just not following your scenerio) When ours are used that way, the Jake will not come on until the service brakes are applied (actually I believe it is triggered by the stoplight switch sending a signal to the ECM) So you "float" the gears just like you would without the Jake brake on. . |
Splitshifter....yes, yours must work differently than mine. With cc on but not active, and jakes enabled...the jakes will activate upon release of the fuel pedal. In order for me to float the gears with jakes enabled I have to hold slight pressure in the clutch freeplay, or not come completely off the fuel pedal during the shift.
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I very, very rarely use my foot brake going down grades, I pull pups for FedEx and 80% of the time the whole truck is 60k gross or less so I have no problem going down grades with my jake on it usually keeps right where I want to be without having to down shift, when I'm done going downa grade is when I usually flip my jake switch to off because I wasnt sure if I would eventually damage something by leaving it on.
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Originally Posted by Rev.Vassago
The only thing you have to really watch is that you aren't using your clutch to keep the jake from engaging by resting your foot on it.
Last year I was told by my trainer to keep my foot on the clutch lightly so that it would not activate in a city or part of highway forbidding engine retarder use. Reason being that if I needed it then I have it ready. The other reason was when I would get through the location I might forget to flip back on and find out as I began going down a grade. I always thought that leaving the clutch partially engaged wore on the clutch, but was told nope. Is this the reason you say not to rest your foot? |
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