Keith H. Posted June 21 Share Posted June 21 I have been driving my 2003 Signature on and off (mostly off) since 2017. i have an Exhaust Brake switch AND pedal. I have flipped it on a few times and stepped on the pedal a few times to see what the difference is when slowing down. It doesn't seem to do anything different. I always thought the engine/exhaust/jake brake were the same and would hear the infamous “drdrdrdrdrdr” sound. Can you feel the brake slowing the coach down or is this a gentle slowdown? I can’t tell if mine is inoperative or not. Can someone explain to me how I can tell the brake is working? Also when should I use it or not use it? Keith Link to comment Share on other sites More sharing options...
Frank McElroy Posted June 21 Share Posted June 21 On my coach if the engine Jake brake is switched ON HIGH, as I pull onto a highway exit ramp, by the time I reach the end to turn, I'll be below 25 MPH. Yes, if the engine brake is working you will absolutely know it - it's like full service brake pressure. But with my DPF engine , there is no straight pipe engine brake sound. You feel the full engine braking but no noise. 1 Link to comment Share on other sites More sharing options...
Ivan K Posted June 21 Share Posted June 21 Keith, you have a Jake brake. Assuming an ISM engine? When you step on the foot switch, you should see the transmission display to select a lower gear. Mine goes to 4th and assuming you are not going too fast for the RPM, it should downshift. This is unmistakable event whether you selected Low or High on the switch. The exhaust note is not necessarily loud but should be noticeable. If none of this happens at speed, the signal is not getting to the ECM and the VIM. 1 Link to comment Share on other sites More sharing options...
Keith H. Posted June 21 Author Share Posted June 21 Thanks guys! I’ll check in the morning when I go exercise the coach. If I find it not working for sure, as Schwartsinager said, “I’ll be back!” Link to comment Share on other sites More sharing options...
nvrtoofast Posted June 21 Share Posted June 21 I have a 2006. As said previously, there is a significant increase in braking. I run mine 90% of the time. As for the sound, it is quiet compared to a tractor trailer. I hear no audible exhaust burble. Especially not what you're expecting from the tractor trailer side of things. I do hear increased engine noise, this is actually exhaust noise but muffled. The brake sound is muffled enough that it is likely unnoticeable from the exterior. At least I like to think so. If you're not getting a significant increase in braking, I would have it looked at as it is highly useful and has kept me well away from the car in front who decides to brake a tad too late. I also like to use it to reduce wear on the brakes. Link to comment Share on other sites More sharing options...
Les Hurdle Posted June 21 Share Posted June 21 My 2004 Cheetah does not high/low brake switch, right? Previous owner said never to use it above 50mph [as he did] engine does not like that !! Mine seems to work but when I go to speed up, switch it off and accelerate the transition is far from smooth, quite the jerk. How best to use it? L Link to comment Share on other sites More sharing options...
Tom Cherry Posted June 21 Share Posted June 21 7 minutes ago, Les Hurdle said: My 2004 Cheetah does not high/low brake switch, right? Previous owner said never to use it above 50mph [as he did] engine does not like that !! Mine seems to work but when I go to speed up, switch it off and accelerate the transition is far from smooth, quite the jerk. How best to use it? L The following is based on EXPERIENCE...and I can't find any technical info to support it. I noticed that my Exhaust Brake...and I don't have, like you, the INTAKE HEAD or the REAL JACOBS Brake. Just the Cummins factory VGT system... was really harsh and ragged. NOT GOOD. On a whim, I decided it was NOT the brake....but the Transmission. The VGT could NOT be "jerking me around" like that. I did the electronic level checking, exactly....per the manual of the Allison. I do NOT have a Dipstick...but they are notoriously....SOMETIMES, totally in accurate unless you change the fluid and then refill properly and then TEST AND CALIBRATE the dipstick. SO, I added about half a quart of Transynd. Drove that for a while....maybe less than 50 miles. The JERK or the downshift was less abrupt. BUT, not where it was when new or after the first Allison service. NOW....as a point of reference, the second Allison service was done sort of "incorrectly". The tech let all the fluid drain...for a while as he did other stuff. That is a NO NO per Allison. The 19 Quart refill is supposed to be done THEN...not let it sit overnight. The Allison electronic level lights said 3 QUARTS low. OMG. But Allison told me that the level system also "LIED". So they told me to add only ONE quart....drive it and get it really hot and then test. I did that and ended up putting in 2 quarts. Then I did a lot of heavy up and down and such grades and whatever. I NEVER had a leak. OK....so there was NOT any evidence that the Fluid Level was actually correct...but it drove fine. Therefore....I added a second pint or half quart. Now UP to a FULL quart of "added to an LVL OK " tranny. Another improvement. Bottom LINE... Did it again. It is perfect. Just like before. NOW, if you have NOT had the Allison serviced, then it is TIME to do that. Do a FULL FILTER and REFIL. Assuming you have the deep sump MH3000, that is 19 Quarts. ONLY USE TRANSYND...the REAL ALLISON Fluid. OR, I would also consider Mobil 2 Delvac Transynd (TS 295) fluid. THAT IS THE ONLY NON ALLISON brand that I would even think about. That's my take. Folks will scratch their whatevers and say....THAT IS CRAZY. Crazy works....if you do it logically and methodically and with an understanding. Good Luck... Link to comment Share on other sites More sharing options...
Solution Dr4Film Posted June 21 Solution Share Posted June 21 @Keith H. Your initial post could be confusing to some newbies so lets get the terminology correct first. BIG difference between an Engine Brake and an Exhaust Brake. There are excellent explanations on the Internet explaining the differences and how each one works. Your coach has an Engine Brake not an Exhaust Brake. Although I have read where there can be a combination of the two specifically when the Cummins engine came with a Variable Vane Turbo AND an Engine Brake. I went from having an PRXB PacBrake Exhaust Brake on my 02 WIndsor (ISC-350) to a two stage engine brake on my 06 Dynasty (ISL-400-2). I will never go back to an exhaust brake again. However, I had to "learn" how to use it correctly. To get the best efficiency from the engine brake on steep grades I make sure my speed is less than 55 mph. If you normally travel 60-75 mph the speed has to come down to less than 55 for it to really feel a difference. With the larger Cummins engines it's probably not necessarily the same. The larger Cummins engines most likely have a better effect at higher speeds, IDK. On most grades, I start with the engine brake in HIGH and toggle between HIGH and LOW to control my speed. As stated, once my speed is around 54 mph, the HIGH engine brake is turned on. Then once my speed is down around 45-50 mph I toggle it back to LOW. If it increases back to 54 mph I toggle it back to HIGH. Link to comment Share on other sites More sharing options...
Keith H. Posted June 22 Author Share Posted June 22 It WORKS and very well, I might add! Thanks for all the advise on my engine brake! Link to comment Share on other sites More sharing options...
Keith H. Posted June 22 Author Share Posted June 22 On 6/21/2024 at 12:47 AM, Frank McElroy said: On my coach if the engine Jake brake is switched ON HIGH, as I pull onto a highway exit ramp, by the time I reach the end to turn, I'll be below 25 MPH. Yes, if the engine brake is working you will absolutely know it - it's like full service brake pressure. But with my DPF engine , there is no straight pipe engine brake sound. You feel the full engine braking but no noise. It works! it Works! It works! I have an engine brake! 1 Link to comment Share on other sites More sharing options...
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