Jake Brake / Pac brake question

[kgard1225]

I may be asking a dumb question but I am researching for future DP purchase. I have a gasser and have never owned a DP but have been looking at a lot of them. Is the type of supplementary braking written on the control panel ? It seems to me that the majority of people with 40 ft DPs think an engine brake is preferable to an exhaust brake so I am leaning towards the engine brake. I have been to several RV shows, lots, etc. and did not know to look or ask the salesman which type of system the DPs I saw had. Only a few mentions were made of the type of braking. How do I know if the salesman does not have it written on their cheat sheet ? Thanks, Ken

[usersmanual]

barmcd wrote:

tinkerer wrote:
After taking my exhaust brake off three times because it froze open and lubricating it with the proper lubricant it is now seized open again. It makes me wonder how many of these exhaust brake really are functional.

I wondered about that too. My PAC brake downshifts as it applies the exhaust brake so I wasn't sure if it was the brake or the transmission slowing me down so I took it apart. It was working fine luckily.

Instead of all that trouble all u have to do is have someone drive the MH and watch the actuating valve.Activate the brake it will make a fairly loud noise and you will see the valve slam shut.
Also forgot to mention is if your sure your solenoid is working just take the pin out of the connecter and see if valve opens by hand .that's the simplest thing to do

I really like the 2 stage engine brake I go down hills at a controlled 60MPH and rarely have to use the service brakes

[tropical36]

kgard1225 wrote:
I have the tow/ haul mode on my gasser that downshifts in a similar way to the pac brake. I am uncomfortable with the high rpms resulting even though I have been told it will not over rev. It really doesn't give me a sense of absolute control on a steep grade.

This is the function of an Allison transmission for downshifting on it's own, rather than having to doing it manually, like you would with some GM or Ford tranny's maybe.
Has nothing to do with an exhaust brake or other, which you do not have and whether made by jacobs or Pac. The common DP with an exhaust brake, just signals the Allison that a downshift is required and it will do so, once the speed becomes low enough to allow it.

[tropical36]

jplante4 wrote:
The Pac brake is not just an exhaust brake. It works in conjunction with the ECM to pre-select a lower gear (4th or 2nd depending on the programming) and will downshift to a lower gear as soon as the ECM figures it can without exceeding max RPM. Proper use of a Pac brake is to switch it on (some people leave it on all the time), then apply the service brake until the downshifting starts. Additional service brake applications may be required on downgrades. You step on the brake and force the coach to slow down, let the downshift occur and then let the Pac brake control the speed. If you need another downshift, you use the service brake to slow down to force a downshift.

I find that it's best to use the service brakes for limiting the RPM, as well. Not that the speed might become excessive in a steep downgrade, but as the tranny downshifts, the rpm's can climb dangerously high.

[NeverHome2]

The engine brake is a jacobs engineering brake that is mounted over the valves on diesel engine that modifies the timing of exhaust valves opening and closing. The exhaust brake is a quarter turn valve mounted on the exhaust outlet of the turbocharger and the closing of that valve stops the exhaust causing a high pressure in the engine.

There is also a retarder done with the Allison transmission. I don't know how it works having never owned one, though it is said they work very good. Just very expensive.

[J-Rooster]

wolfe10 wrote:
No, Jake Brakes, being internal to the engine (actually just above the head) are pretty bomb proof.

Was this failure on an RV or on a high mile OTR truck? I have no experience with the high mile truck world.

Brett, it was a long time ago on a 1967 Kenworth with a 335 Cummins engine. Thanks for your response!

[wolfe10]

No, Jake Brakes, being internal to the engine (actually just above the head) are pretty bomb proof.

Was this failure on an RV or on a high mile OTR truck? I have no experience with the high mile truck world.

[J-Rooster]

wolfe10 wrote:
Easy to determine if the exhaust brake is working.

Down arrow to a gear-- 4th is a reasonable choice in most areas.

Accelerate to higher RPM in that gear.

Turn the exhaust brake on and off. Since the transmission is locked in that gear, it is a CONSTANT. If you don't feel additional braking, particularly at higher RPM, it is not working.

Brett, when I had trouble with a Jake Brake happened several times I had to take the Jake Head valve cover off and replace a spool valve spring! Have you ever encountered this?

[kgard1225]

I have the tow/ haul mode on my gasser that downshifts in a similar way to the pac brake. I am uncomfortable with the high rpms resulting even though I have been told it will not over rev. It really doesn't give me a sense of absolute control on a steep grade.

[wolfe10]

Easy to determine if the exhaust brake is working.

Down arrow to a gear-- 4th is a reasonable choice in most areas.

Accelerate to higher RPM in that gear.

Turn the exhaust brake on and off. Since the transmission is locked in that gear, it is a CONSTANT. If you don't feel additional braking, particularly at higher RPM, it is not working.

[Big_Katuna]

Mine is like slamming the brakes on when it activates.

[barmcd]

tinkerer wrote:
After taking my exhaust brake off three times because it froze open and lubricating it with the proper lubricant it is now seized open again. It makes me wonder how many of these exhaust brake really are functional.

I wondered about that too. My PAC brake downshifts as it applies the exhaust brake so I wasn't sure if it was the brake or the transmission slowing me down so I took it apart. It was working fine luckily.

[tinkerer]

After taking my exhaust brake off three times because it froze open and lubricating it with the proper lubricant it is now seized open again. It makes me wonder how many of these exhaust brake really are functional.

[Blaster_Man]

gsander1 wrote:
My 2003 Magna with a C12 has a 3 stage Jake brake. There are two switches involved. One activates the Jake while the other is three position 2, 4 or 6 cylinders.

My 500HP Detroit Diesel works the same way.

[J-Rooster]

Big Katuna wrote:
I have an 05 Fleetwood DP with exhaust brake. It works just fine in the mountains; rarely have to use the foot brake BUT its a 30,000 pound RV not a 40,000 pound 44 footer.

Most entry level DPs are going to have exhaust brakes. Few have retarders; most if not all Foretravels do. They do raise the trans temp a little.

retarders is the word that I used (except the ers was left out), and it was ****** out! What's up with that it's in the dictionary?