I've been a truck nut all my life starting as a little kid, my Grandma lived near a main road and a trucking company wasn't too far away with Mack B and F models passing by all the time. I always ran to the window or roadside to watch the trucks drive by when I heard them. As I got older I learned of the different engine manufacturers and got to where I could identify the engine brand in a truck by the sound it made. The early Detroit engines were easy to identify, the differences between Cat and Cummins were much more subtle. Mack had its own unique sound as well. Those engines always had an exhaust growl to them regardless of how well muffled they were. I think it's safe to say that Cummins became the most popular engine over time and I became very accustomed to hearing them, especially pulling away from traffic lights. I drove trucks both in construction and freight for 20 years with each of the engines I mentioned too. Lately though in the newest trucks I'm hearing something entirely different. When they leave a stoplight I really don't hear any exhaust at all, just a God-awful racket coming from under the hood. The best way I can describe it is sounding like an old baling machine in need of greasing! I'm hearing the same sound between different brands of new trucks so I guess its a result of engine design. Had I heard this sound in earlier trucks I'd have guessed there was a terminal problem about to implode. I've never heard a smooth running machine sound like this without having a major problem. So I'm curious. Those of you who work in the industry, can you explain to me what's going on here? What part of the engine is making this awful noise and why don't they self-destruct?
The dump truck company we use has 6-8 newer KW tri-axles and I haven't noticed any bad sounds from under the hood just a muffled exhaust. Now they have a few 3406's and C15's that are tuned in and sound awesome!
I can't really say I hear anything different-because most all new engines have a governed rpm at 1800. The dpf/cat system cuts exhaust noise. Other than the cooling fan. Freightliners with the DT12 or Eaton auto shifts make some noise shifting but not all that much.
They all sound dead quiet to me compared to the clatter and rattle of the old days. They all have pretty much the same injection system now which is where the majority of the "character" used to come from.
On starting out from a stop if AMT didn't drop all the way to 1st you can hear two rapid down shifts as air is exhausted from shift control.
The maxxforce stands out to me, can hear that POS from a mile away but other then that they sound similar. Easy to pick out deleted trucks though.
Steve, Interesting observation. I’ve taken notice of the unique sound of late model common rail engines, as well. Speaking generally. Common rail injectors sound like a machine gun rattling. The other contributing factor is the gear train requirements needed to drive the uber high-pressure fuel pumps. Plus, many of the OEM’s have moved the gear trains to the rear of the engine to help reduce the rattling. Peak torque ratings have moved lower on the RpM scale and that has created weird low-rpm harmonics that rattle the clutch and transmission like crazy. The DD15 with the weird turbo compounding system has it’s unique sound.
We have 15's and 16's-the only ones I have seen that on are the 16's. Also we have all those engines {US Food} running out if our yard every day, I don't hear anything different. The sound he is hearing [especially with a DD 15 and DT 12 transmission is the rapid air exhausted from down shift. Most of the time when coming to a full stop they will drop to D2 or D3 then starting out drop to D1 with a full load. At least that's what I believe.
How many trucks are being built with manual transmissions now?
I hear ya Steve, these days all I can hear from the new trucks is the hurricane roar of the engines fan. I just retired from a 2011 KW with an ISX500 and it was just plain annoying. And the fan always seem to come on when I was in the dirt. Now, having said that, the best sounding truck I ever drove was a 55 Diamond-T, 262 fitted with a T-506 turbo and straight 5" stack, cut short at the top of the cab. Always had that right window slightly open....
I was on a job the other day and heard a pickup coming up the hill.... "That must be Teddy" "Naw, Teddy's got a new rig can't even hardly hear it, that's an old Super Duty, must be Bill"
Maybe 20 to 25%
I often times find myself working near traffic lights so I'm hearing the trucks accelerate from a stop, and yes, I have noticed a higher percentage of trucks equipped with automatics. That being said, the sound I'm trying to describe is the same for both auto and standard shift and it's coming from the engine. Coaldust may have hit on something, I've been away from heavy trucks for about 20 years and know very little about the most recent power plants. I've wondered if the knocking/vibrating I'm hearing could be felt through the steering wheel or clutch on trucks equipped with one. Like I mentioned earlier, had I not heard this same noise coming from almost every new truck I see I'd have thought it was coming apart. I started paying attention to brands since I posted and it's been in a number of Peterbilts, Kenworth, Freightliner and Western Star. Heard an International Lonestar making the racket too. I guess you could describe it as similar to a rod knock or an extremely loud lifter tap, kind of makes me cringe at what must be happening to make all that noise.
new mack engines have a rrrrrrrrinkiiitinktink sound to em
Lots of air compressors make lots of noise.
I'm just trying to understand this question because to me, the new engines all sound extremely smooth and quiet compared to the old days. Except for the small Internationals which are rapidly becoming extinct because of their problems, those things have a lot of knocking noises to them.
The older engines had a lot less control of the injection timing an were limited in power by the injection pressure. The injection duration was longer raising emissions. With the high injection pressures the timing on the newer engines do not need to be as far advanced. The more advanced the timing was the louder the diesel rattle sound.
My px-8 in my kenworth sounds awful to me at an idle. I cringe every morning when I go out and hit the key. From inside the cab I can’t hear it and it runs smoothly though. My last truck had a 24 valve Cummins and no muffler. I wasn’t sneaking up on anyone.
Some engines just have the luck some don't. I've seen a old 335 Cummins you could balance a dime on. Others just rough no matter what tuning was done. Some Cat engines under hard throttle smooth as could be others just not so. But every engine has it's own characteristics. Most all of these new engines are pretty smooth {imo} especially for being able to deliver the amount of torque at 1300.
To cheer you up, I'll record an audio of my 855 Big Cam 3 some day soon and post it. Are we allowed to post audio files here?
I think what you are hearing is the multiple injections per power stroke. With the high pressure/short injection time its really a series of explosions. I have a T4 Deere 9L, and at idle you can't hold a conversation within 20 feet. I swear its almost as noisy as my 6-71.
There is something pleasant about indirection injection sound. An old 7.3 IDI makes a racket, but the sound is pleasant to my ears. A 7.3 PSD makes a much sharper sound. We have single-shot Rosewoods on one 2000 PSD and the sound is not friendly. It turns heads at the grocery store, making greenies angry.