Jake Brake

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Jake Brake

October 09, 2013, 01:49:41 pm

This one's addressed to the few of us that have Jake Brakes rather than retarders. On this rig, the Jake is set up to preselect 4th gear and it is a one speed Jake. i.e. all six cylinders. This setup is somewhat restrictive. It works best at 50 mph and below. For example, on a long 6% grade, you don't need to use the service brakes. Matter of fact, you have to disengage the Jake from time to time. The problem for me is at higher speeds. Say you are descending a long mild grade and wish to maintain 60 mph. If I use the Jake in this situation, it will seek 4th and as soon as it slows enough it will shift. This sends the tach over 2K which is the governed speed on our M11.

So how about this idea? What if I have Cummins change it to preselect 5th and allow me to manually select 4th? Anyone done this? Good idea?

Also, it's a weird switching arrangement (surprised Triana too). There are two rockers, both labeled "retarder." One enables the system and illuminates when you switch it on. The other actually engages the Jake and causes the Allison to seek 4th. This one illuminates when the Jake is functioning. Don't know why FT chose to use two switches.
jor

Re: Jake Brake

Reply #1 – October 09, 2013, 02:58:12 pm

FYI, you would have ALLISON, not Cummins reprogram the Jake Brake "pre-select gear" to 5th.

Have done this on both our coaches.

Takes 10 minutes from the Allison diagnostic plug.

You might also check with James and/or Cummins to see if you can have a two stage (high/low= 6 cylinders/3 cylinders) Jake programmed/wired. Most other coach makers with Jake brakes DO have two stage Jake brakes.

Brett

Re: Jake Brake

Reply #2 – October 09, 2013, 03:13:53 pm

Thanks. After reprogramming can you still downshift manually into 4th and 3rd?
jor

Re: Jake Brake

Reply #3 – October 09, 2013, 03:47:25 pm

Quote from: jor – October 09, 2013, 03:13:53 pm

Thanks. After reprogramming can you still downshift manually into 4th and 3rd?
jor

Yes, no change in ability to use up and down arrows to choose the gear you want.

Re: Jake Brake

Reply #4 – October 09, 2013, 04:23:15 pm

Jor
If you are going to fast , say 70mph and engage the Jake Brake I think it will go into 5th gear until speed is low enough so it can down shift again without exceeding the governor limit.

Re: Jake Brake

Reply #5 – October 09, 2013, 06:14:08 pm

John,
That is the way it works but it shifts from 5 to 4 at a speed that .makes me nervous. The tach (VMS) will swing up to almost 2100. The
Governed speed is 2000 and blow up fly apart speed is 2300. I'm not sure how high the Allison will allow the Cummins to go in a downhill situation.

Found both Cummins and Allison in Eugene btw.
jor

Re: Jake Brake

Reply #6 – October 09, 2013, 06:50:31 pm

Jor,
I guess you need to talk to Allison/Cummins to be sure but I think it will up shift before it over speeds the engine.
You might get there opinion on whether it is hard on the engine or transmission to operate it this way.

Re: Jake Brake

Reply #7 – October 09, 2013, 09:02:26 pm

Quote from: jor – October 09, 2013, 06:14:08 pm

John,
That is the way it works but it shifts from 5 to 4 at a speed that .makes me nervous. The tach (VMS) will swing up to almost 2100. The
Governed speed is 2000 and blow up fly apart speed is 2300. I'm not sure how high the Allison will allow the Cummins to go in a downhill situation.

Found both Cummins and Allison in Eugene btw.
jor

Jor,
I believe you are electronically governed at 2100 rpm. But best call Cummins at 1-800-343-7357, with your model and engine s/n handy and ask them.

Re: Jake Brake

Reply #8 – October 09, 2013, 09:14:50 pm

I do like the jake idea. Used parts are around on the Internet. Only had one customer ever exceed the retarder heat limit. 1989 U300 Unihome. He laughed. It was in Alaska.

He tried in the lower 48 just to see. Early u300 were fairly light in comparison.

Belt and suspenders?

Two position would be of interest at least. Old marquis had three positions on 3176's

Bob

Bob

Re: Jake Brake

Reply #9 – October 09, 2013, 09:33:06 pm

We're in the area (Eugene) for a few days. I plan to have Allison change the preselect from 4th to 5th and have Cummins rewire for a 2 speed Jake. Might have to do it on the return trip. Tomorrow I'm going to try and ID an extra wire from the dash to the back end. If I can do that it should make the 1 speed to 2 speed change a lot easier.
jor

Re: Jake Brake

Reply #10 – October 09, 2013, 10:09:27 pm

On our 91 GV there is an "exhaust brake" with a pedal just to the left of the steering column. It is an electrical switch that closes a damper in the exhaust just down stream of the turbo. It is difficult to tell if it is working or not and doesn't seem to do anything at rpms less than about 1500. It is slightly detectable at around 2500 rpm. Is this normal or do I need to fix something here? Thank you and have a great day ---- Fritz

Re: Jake Brake

Reply #11 – October 09, 2013, 10:21:16 pm

Quote

Is this normal or do I need to fix something here?

The higher the revs the better that exhaust brake will work. Downshift and let it slow you down. Ideally you can get to the point where it holds your speed steady with an occasional stab at the service brakes.
jor

Re: Jake Brake

Reply #12 – October 10, 2013, 08:32:24 am

Quote from: fkjohns6083 – October 09, 2013, 10:09:27 pm

On our 91 GV there is an "exhaust brake" with a pedal just to the left of the steering column. It is an electrical switch that closes a damper in the exhaust just down stream of the turbo. It is difficult to tell if it is working or not and doesn't seem to do anything at rpms less than about 1500. It is slightly detectable at around 2500 rpm. Is this normal or do I need to fix something here? Thank you and have a great day ---- Fritz

Fritz,

The effectiveness of an exhaust brake depends on three primary things:

Allowable back pressure allowed by engine manufacturer. Earlier engines had less strong exhaust brake return springs, and therefore could tolerate less back pressure.

Engine RPM. With standard exhaust brake, you need to be at higher RPM for the brake to be effective. The PacBrake PRXB addressed this by generating max allowable back pressure at lower engine RPM.

Transmission gear (lower gives more braking HP) and presence/absence of lock up converter. The 6 speed 3000 and 4000 series Allisons have torque converter lockup in 2-6th gear. Makes a big difference.

Brett

Re: Jake Brake

Reply #13 – October 10, 2013, 10:33:14 am

Thanks for the input and have a great day ---- Fritz

Re: Jake Brake

Reply #14 – October 11, 2013, 01:14:54 am

Let me know how the rewire goes. I talked to James about it years ago. No answer from the company on why they didn't wire it hi/lo My 95 has the jake.

Re: Jake Brake

Reply #15 – October 11, 2013, 03:25:57 am

My 95 has the 2 position Jake brake. I thought they all did.

Re: Jake Brake

Reply #16 – October 11, 2013, 10:15:46 am

Well now, this is pretty interesting. According to JamesT, Foretravel never sold other than a one speed Jake. My schematic shows a one speed wired from low/medium. That schematic was retired a few coaches after ours, build number 4721 in January, 1995.

Lon, do you happen to have a schematic of yours? Also, how do you use it (on/off and a 2 position switch?)? It would be neat if I could use existing switches to change to a two speed. I'm thinking my on/off could stay as is and the other's current off position could be low.

Apparently, it's no big deal with the hardest part being running a wire from the dash to the engine. We all have extra wires so that's not problem.

I'll post on the process.
jor

Re: Jake Brake

Reply #17 – October 11, 2013, 12:12:13 pm

Quote from: jor – October 11, 2013, 10:15:46 am

Well now, this is pretty interesting. According to JamesT, Foretravel never sold other than a one speed Jake. My schematic shows a one speed wired from low/medium. That schematic was retired a few coaches after ours, build number 4721 in January, 1995.

Lon, do you happen to have a schematic of yours? Also, how do you use it (on/off and a 2 position switch?)? It would be neat if I could use existing switches to change to a two speed. I'm thinking my on/off could stay as is and the other's current off position could be low.

Apparently, it's no big deal with the hardest part being running a wire from the dash to the engine. We all have extra wires so that's not problem.

I'll post on the process.
jor

So you two 95's both have jakes and the 4060r trans? How about a comparison of how they work and how you use the two systems?

And why?

Bob

Re: Jake Brake

Reply #18 – October 11, 2013, 04:02:04 pm

Quote

How about a comparison of how they work and how you use the two systems?

We have the 4060 but no R. Our last coach had a similar engine (ISM vs. M11) and a retarder. The retarder is a lot more versatile. The Jake does the job on downgrades but doesn't stop the coach the way a retarder does, for example, when rolling to a stop. When I get ours rewired as a 2 speed and reprogramed to pre select 5th instead of 4th, it will be much better. Bottom line: the Jake provides you with safe descends but doesn't measure up to a retarder. Nevertheless, I'm having a lot of fun with it. The one advantage is that you don't have any concern with transmission temps but then, I never had an issue with them with our retarder. Different strokes.
jor (using joody's account)

Re: Jake Brake

Reply #19 – October 11, 2013, 07:10:09 pm

My 95 was one of the first u320`s (unicoach)made.
I will look up the build number when i get home.
The Jake has 2. Switches,one selects 3 or 6cyl,the other turns it.on and.off.
I leave.it.in full on (6cyl). The other switch position has.much.less effect on braking.
Im still learning the. system,i have.not driven.the coach enough under differant situations to be.able.to write in depth about its function.
Sure does slow it down well.

Re: Jake Brake

Reply #20 – October 11, 2013, 10:19:17 pm

Quote

The Jake has 2. Switches,one selects 3 or 6cyl,the other turns it.on and.off.

That's what I have in mind for ours too. Interestingly, the schematic shows one wire from what would be "low" and "medium." I'm assuming low is all six but you'd think the other would be high rather than medium. Anyhow, I'll find out when Cummins makes the change.
jor

Re: Jake Brake

Reply #21 – October 12, 2013, 12:10:09 pm

Low is three cylinders. High is all 6. Newer jakes are 3 stage - 2, 4 and 6.

I guess the DD 60s just have a high/low.

Re: Jake Brake

Reply #22 – October 16, 2013, 10:08:55 pm

Well, they couldn't find an exact match for the switch in our 95 so we put the 2 stage Jake on hold until they can locate one. We did, however, get the pre-select changed from 4th to 5th. Did that down the street at Pacific Truck Centers. Had to wait a couple of hours but get this... the bill was $34. When was the last time you walked out of a truck service for that kind of money!

Quote

The Jake has 2. Switches,one selects 3 or 6cyl,the other turns it.on and.off.

Lon and Cheryl, any chance you can share with me your schematic on your 2 speed Jake? Here's mine. The Engine Brake Select has 2 green wires (#227) combined and attached to the switch. Could it be as simple as separating those wires and wiring up a 2 speed toggle? I'm thinking yes. Anyhow, I'd love to see your schematic or anyone else that has a 2 speed. Thanks.
jor

* Added a photo of the select switch showing the two wires

Re: Jake Brake

Reply #23 – October 17, 2013, 11:03:25 am

Quote from: jor – October 16, 2013, 10:08:55 pm

Well, they couldn't find an exact match for the switch in our 95 so we put the 2 stage Jake on hold until they can locate one. We did, however, get the pre-select changed from 4th to 5th. Did that down the street at Pacific Truck Centers. Had to wait a couple of hours but get this... the bill was $34. When was the last time you walked out of a truck service for that kind of money!
Lon and Cheryl, any chance you can share with me your schematic on your 2 speed Jake? Here's mine. The Engine Brake Select has 2 green wires (#227) combined and attached to the switch. Could it be as simple as separating those wires and wiring up a 2 speed toggle? I'm thinking yes. Anyhow, I'd love to see your schematic or anyone else that has a 2 speed. Thanks.
jor

* Added a photo of the select switch showing the two wires

Jor,
Can you give us a report on how the downshift to 5th works out for you. I was scheduled to have mine reprogrammed but they had an emergency and I could not wait around so mine is still downshifting to 4th.
And they wanted $100.00 down in FL.
Thanks,
Rick

Re: Jake Brake

Reply #24 – October 18, 2013, 04:07:29 am

Quote from: jor – October 16, 2013, 10:08:55 pm

Well, they couldn't find an exact match for the switch in our 95 so we put the 2 stage Jake on hold until they can locate one. We did, however, get the pre-select changed from 4th to 5th. Did that down the street at Pacific Truck Centers. Had to wait a couple of hours but get this... the bill was $34. When was the last time you walked out of a truck service for that kind of money!
Lon and Cheryl, any chance you can share with me your schematic on your 2 speed Jake? Here's mine. The Engine Brake Select has 2 green wires (#227) combined and attached to the switch. Could it be as simple as separating those wires and wiring up a 2 speed toggle? I'm thinking yes. Anyhow, I'd love to see your schematic or anyone else that has a 2 speed. Thanks.
jor

* Added a photo of the select switch showing the two wires

I will look through my files for that info.

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