4x4 electronic shift/exhaust brake vacuum?

[KWinterborne]

Recently picked up my new truck and am curious if this is normal. After I tried testing the 4x4 electronic shift feature, I found that the vacuum continued to run even after I had shut the truck off and restarted it. It seems to shift OK in and out of 4x4. But once I move the switch and the vacuum turns on it will continue to run. I haven’t fully troubleshot the conditions yet, but I believe once I give it a bit of throttle it shuts off but once I let go of the throttle or come almost to a complete stop it turns on again. Eventually if I don’t use the 4x4 switch again it will stop running.

Also, would there be any connection to this vacuum controller and the exhaust brake? When my exhaust brake kicks in I hear it in the exhaust but I also here the vacuum running again. Once I get slow enough to where the exhaust brake turns off the vacuum also turns off (assuming it’s not running due to me shifting the 4x4 mode).

Ken

 

[Dieselnerd]

Mine is an '05 but I assume the electronic shift is the same. No noise at all, just shifts when you turn the knob. There is no vacuum involved just electric shift motors. Since I don't have an exhaust brake I don't know how it is actuated in your '06 but there is no vacuum pump on the '05.

 

[KWinterborne]

Hmmm, I just assumed it was vacuum activated as I hear one kick in when I flip the switch.

 

[KWinterborne]

I haven't switched into 4x4 the last couple of days and did not hear the vacuum at all this morning, not even from the exhaust brake. So guess I'll switch to 4x4 tonight and see what happens.

Ken

 

[jelag]

I haven't seen the vacuum circuit on the exhaust brake but I assume that the vacuum pump runs all the time and only when the solenoid is turned on by the ecm does vacuum pull the brake into action... . and I assume that once the brake is turned off... vacuum pulls the brake off..... or its spring loaded... .



You should not be able to hear any vacuum leaks or it moving in the tubing... . if you can, its a leak... . and you'll need to find it.....



If you take a long hose... . usually 3 or 4 ft of 5/8 or 3/4" heater hose. . put one end to your ear and move the other end end where you think there might be a leak... the sound of the leak will transmit through the hose and its easy to hear... . I use this for air leaks, vacuum leaks etc... .



Hope this has helped...

 

[BHolm]

The Mopar jake brake uses vacuum to engage the brake and spring pressure defaults the brake to the off position when the vacuum is taken away. On mine the vacuum pump makes a fair amount of noise when engaged and still makes some noise when not engaged. The pump is on the belt so it turns all of the time. I don't think it is correct to assume it shouldn't be making any noise, how would that be possible? I have followed the plumbing on mine more than once thinking it had to be leaking somewhere, but the noise comes from the pump itself not any of the hoses or connections. Mine seems to work well so I am doubtful that there is any problem. I have accepted the noise as normal.

 

[KWinterborne]

The Mopar jake brake uses vacuum to engage the brake and spring pressure defaults the brake to the off position when the vacuum is taken away. On mine the vacuum pump makes a fair amount of noise when engaged and still makes some noise when not engaged. The pump is on the belt so it turns all of the time. I don't think it is correct to assume it shouldn't be making any noise, how would that be possible? I have followed the plumbing on mine more than once thinking it had to be leaking somewhere, but the noise comes from the pump itself not any of the hoses or connections. Mine seems to work well so I am doubtful that there is any problem. I have accepted the noise as normal.

I agree with you that the jake brake noise is probably normal albeit somewhat annoying. But what about when you shift into and out of 4x4? As soon as I move the switch I hear a pretty loud vacuum kick on which I assume is to activate the transfer case linkage. But after it is done shifting the vacuum continues to run. I liked to switch to 4 lo just to make backing into my driveway a bit easier (due to low range). I then switch back to 2WD after I park and the vacuum continues to run. I started the truck the next day and the vacuum was still running the entire time to my work. At some point, it did finally stop running.

Ken

 

[amsoilman]

I agree with you that the jake brake noise is probably normal albeit somewhat annoying. But what about when you shift into and out of 4x4? As soon as I move the switch I hear a pretty loud vacuum kick on which I assume is to activate the transfer case linkage. But after it is done shifting the vacuum continues to run. I liked to switch to 4 lo just to make backing into my driveway a bit easier (due to low range). I then switch back to 2WD after I park and the vacuum continues to run. I started the truck the next day and the vacuum was still running the entire time to my work. At some point, it did finally stop running.



Ken

I believe the 2003 and up Automatics are the only trucks that have a vacuum pump of any sort, but only used for cruise control. I may be wrong, but my 03 6-speed does not use vacuum for the 4X4 shift linkage! It is done by an electric motor. Now the E-Brake (jacobs) is operated with a vacuum pump, which I installed when the E-Brake was installed.



Wayne

 

[KWinterborne]

Turns out I was interpreting my symptoms incorrectly. Upon further testing, switching into/out of 4x4 does not use a vacuum (as you all have said). It is the exhaust brake vacuum that I hear. I had pretty much left in on ever since I picked the truck up. It still seems to be intermittent though as far as when I am sitting at an idle. Sometimes it is running and other times it is not. But at least now I know I can just turn the exhaust brake off and that will turn the vacuum off.

Ken

 

[KWinterborne]

Thought I would bring some closure to this. Turns out everything is working normal. The intermittent on off at idle has to do with the temperature of the transmission. When it’s cold, the exhaust brake and its vacuum is on to assist in warming up the truck when at idle. Once it’s warmed up, the only time you should hear it is when it is actually in use (decelerating). Guess it helps to read the manual/instructions.

Ken