speedracer1407 Posted June 4, 2009 Report Share Posted June 4, 2009 After riding on a #1930+ NF equipped with the Allison B-400R transmission, and watching many pull away from the Michigan/Huron stop while waiting fo the 147, I've noticed a sound that seems to be transmission related, in part because it doesn't happen on the ZF equipped NFs. If the driver accelerates at any speed, and for any amount of time, and then lifts off the gas, a loud single blast of air is released from the rear of the bus behind the wheels. It's loud enough to startle from the outside, and it'll kick up a plume of dust in the right conditions. Normally, I'd just assume this was the result of some modification to the bus's existing pneumatic brake or suspension systems applied to 1930+ buses. But because it *always* happens at the moment the driver lifts off the pedal after accelerating, I suspect that it's unique to the Allison transmission itself. It's too consistent to be coincidence; while riding on one a few weeks ago, it happened each and every time the driver lifted off the pedal after accelerating, and only at those times. Can anyone confirm that the Allison transmission has some pneumatic component that would cause this sound? Quote Link to comment Share on other sites More sharing options...
T8H5307A Posted June 4, 2009 Report Share Posted June 4, 2009 Can anyone confirm that the Allison transmission has some pneumatic component that would cause this sound? It's the retarder disengaging. It happens right before you come to a stop or when you go to accelerate after slowing down Quote Link to comment Share on other sites More sharing options...
jacksone44 Posted June 4, 2009 Report Share Posted June 4, 2009 It's the retarder disengaging. It happens right before you come to a stop or when you go to accelerate after slowing down I've been trying to answer that question for 9 years believe it or not. Im from St. Louis and the first order of 40ft Gilligs (received in 2000) have the same transmission's and do the SAME THING. For some stupid reason I kind of like it.... but it seems like it happens when the operator is takes his/her foot off the brake or the bus comes to a complete stop when it happens. Quote Link to comment Share on other sites More sharing options...
trey824 Posted June 5, 2009 Report Share Posted June 5, 2009 I've been trying to answer that question for 9 years believe it or not. Im from St. Louis and the first order of 40ft Gilligs (received in 2000) have the same transmission's and do the SAME THING. For some stupid reason I kind of like it.... but it seems like it happens when the operator is takes his/her foot off the brake or the bus comes to a complete stop when it happens. its not stupid at all because i love it my self.i even mock the bus when i see one with the allison stoping and people look at me crazy.but i love that quantity of new flyers,too bad there all not like that. Quote Link to comment Share on other sites More sharing options...
NewFlyer0627 Posted July 22, 2009 Report Share Posted July 22, 2009 its not stupid at all because i love it my self.i even mock the bus when i see one with the allison stoping and people look at me crazy.but i love that quantity of new flyers,too bad there all not like that. Yes it is a sweet sound that comes from the Buses, because all the buses in my local trasit fleet doing the same sound sfx. cta New Flyer Buses #1930+ are the same buses as what I deal with in my city just the only difference is the paint scheme. Also, just to put out there the Allison B500R Transmission features the same thing!!! Quote Link to comment Share on other sites More sharing options...
dann Posted July 22, 2009 Report Share Posted July 22, 2009 After riding on a #1930+ NF equipped with the Allison B-400R transmission, and watching many pull away from the Michigan/Huron stop while waiting fo the 147, I've noticed a sound that seems to be transmission related, in part because it doesn't happen on the ZF equipped NFs. If the driver accelerates at any speed, and for any amount of time, and then lifts off the gas, a loud single blast of air is released from the rear of the bus behind the wheels. It's loud enough to startle from the outside, and it'll kick up a plume of dust in the right conditions. Normally, I'd just assume this was the result of some modification to the bus's existing pneumatic brake or suspension systems applied to 1930+ buses. But because it *always* happens at the moment the driver lifts off the pedal after accelerating, I suspect that it's unique to the Allison transmission itself. It's too consistent to be coincidence; while riding on one a few weeks ago, it happened each and every time the driver lifted off the pedal after accelerating, and only at those times. Can anyone confirm that the Allison transmission has some pneumatic component that would cause this sound? I heard the same thing while riding 2024 on Route 76 the other day. As long as it's not a mechanical malfunction and people think it sounds cool, I'll have no problem with that. Quote Link to comment Share on other sites More sharing options...
Nabi60SFW9620 Posted July 23, 2009 Report Share Posted July 23, 2009 One thing about Allison B400R. It doesnt whine really loud like the Voith D864.3 does. Sometimes it can be hard to tell what engine a coach has if the transmission is a Voith. Especially on Gilligs. Quote Link to comment Share on other sites More sharing options...
geneking7320 Posted July 28, 2009 Report Share Posted July 28, 2009 Reading this thread brings to mind that I've heard an "air discharge" sound from the Flxible 6000s and also from SEPTA Neoplans back in 1999. I've only noticed that sound from CTA's 1000s this year. Quote Link to comment Share on other sites More sharing options...
daerah Posted September 18, 2009 Report Share Posted September 18, 2009 The sound we all are referring to, is commonly called the retarder spit. Bascially, its a spit-valve. It releases air, after the retarder is "disengaged" Allison B400s are most known for this...and YES I do love that sound too. More than likely, you'll mostly hear on it on Allison systems. Though, to my sudden surprise, certain ZF transmissions make that retarder spit-valve sound too. Ive heard it on New Flyer L40LF (Liquified Natural Gas) buses in Santa Monica, CA "Big Blue Bus"..the sound is softer, but you can hear it. The way it works is simple. While accelerating, or (while your foot is on the accelerator and then you take your foot off the pedal) You'll hear a "tick" sound first from the back "engine compartment", and bus immediately begins slowing... (I'm emphasizing "immediately" because one: you can feel the braking affect, & two: ZF transmissions dont start braking the speed down, until after a few seconds, like 5-8 seconds, so its more gradual than an immediate)...once you put your foot back on the accelerator and give it some gas, the "spit" air sounds...meaning the retarder is coming off... OR...when you're on the service brake, and coming to a complete stop, the retarder "spit" sounds once the bus gets below 10mph or shifts into first (1) gear. Most retarders automatically disengage after 10mph. The 900s (ISE) were 5mph before they were modified, making it VERY difficult to stop smoothly. 1 Quote Link to comment Share on other sites More sharing options...
daerah Posted September 18, 2009 Report Share Posted September 18, 2009 It's the retarder disengaging. It happens right before you come to a stop or when you go to accelerate after slowing down Basically, I co-sign with your reply. lol. Quote Link to comment Share on other sites More sharing options...
speedracer1407 Posted September 18, 2009 Author Report Share Posted September 18, 2009 The sound we all are referring to, is commonly called the retarder spit. Bascially, its a spit-valve. It releases air, after the retarder is "disengaged" Allison B400s are most known for this...and YES I do love that sound too. More than likely, you'll mostly hear on it on Allison systems. Though, to my sudden surprise, certain ZF transmissions make that retarder spit-valve sound too. Ive heard it on New Flyer L40LF (Liquified Natural Gas) buses in Santa Monica, CA "Big Blue Bus"..the sound is softer, but you can hear it. The way it works is simple. While accelerating, or (while your foot is on the accelerator and then you take your foot off the pedal) You'll hear a "tick" sound first from the back "engine compartment", and bus immediately begins slowing... (I'm emphasizing "immediately" because one: you can feel the braking affect, & two: ZF transmissions dont start braking the speed down, until after a few seconds, like 5-8 seconds, so its more gradual than an immediate)...once you put your foot back on the accelerator and give it some gas, the "spit" air sounds...meaning the retarder is coming off... OR...when you're on the service brake, and coming to a complete stop, the retarder "spit" sounds once the bus gets below 10mph or shifts into first (1) gear. Most retarders automatically disengage after 10mph. The 900s (ISE) were 5mph before they were modified, making it VERY difficult to stop smoothly. Thanks for the detailed answer! I still wonder, though, why there's a pneumatic component to the transmission. The retarder is hydraulic, forcing oil through a series of rotors and stators, which puts drag on a shaft, which transmits that drag to the output shaft of the transmission. Quote Link to comment Share on other sites More sharing options...
ZH1287 Posted September 18, 2009 Report Share Posted September 18, 2009 Thanks for the detailed answer! I still wonder, though, why there's a pneumatic component to the transmission. The retarder is hydraulic, forcing oil through a series of rotors and stators, which puts drag on a shaft, which transmits that drag to the output shaft of the transmission. I'm not sure about the Allisons but, the all the ZF's before the 1000 series had an air powered accumulator for the retarder. This basically pre-pressurized fluid so the retarder would begin braking faster. Quote Link to comment Share on other sites More sharing options...
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