CAT 3126 with a nasty GROWL

[Native]

Originally Posted by Jolly Roger bus 223

i have heard that before and its usually a rear end noise,
most likely the universal joint being wore out messed up the pinion bearing going into the rear end and now that the the driveline is tightened up then it is showing the true restraint on the driveline or did the drive line cause the pinion bearing problem?
just my opinion
what rearend would help us know if the differential could be pulled toward the driveshaft or if the whole center section has to be dropped? either way the axles have to be out a little and more on others.
more info on your rear end if the phasing of your drive shaft is correct?
is your tranny output shaft leaking now?
is your rear end front seal leaking now ?
were either leaking before?

I have heard differential whines before and there *is* some differential whine.
Both the transmission output and the differential front seal are dry and have been as long as we have owned the vehicle. No leaks.

[Mountain Gnome]

Originally Posted by Native

It is not really speed related. In 4th, I can hear it a little when the engine speed is 1800 RPM to 215 RPM. Once I get past that and I can get up to 55 MPH with no GROWL ... albeit at 2500 RPM. As soon as it shifts into 5th (overdrive) the RPMs drop down to 1800 RPM and the GROWL starts and continues until about 2150 RPM (60 MPH). This is why I think there are two components to the noise. One is related to vehicle speed and the other is related to engine load.

yea, somehow I got that part confused, and realized a minute later. working by memory from earlier or yesterday or something. Sorry.

Originally Posted by Native

While I do have a set of 20-ton jack stands and a 20-ton jack, I am not quite ready to jack it up and have the rear wheels spinning.

you don't really have to crawl under it. I've had a vehicle on 4 solid jackstands and idling in 5th gear before, and crawled under. It's not so bad...
But really, if you stay out from under it, just get the rear tires 1" off the pavement with the front tires chocked. Then see what you can hear.

[Native]

No promises ... I still have to clear that with my wife! Honey, is my life insurance paid?


I will be crawling under for a more in-depth look with it NOT RUNNING after taking care of a few other things that life brings to life itself.

[banman]

Originally Posted by Native

I had that same thought earlier today. Placing microphones all along the drive train would help diagnosing this problem.
SNIP...

The Vibrex was a way of life for me --
Wonder if there's a big truck equivalent for measuring driveline vibrations...

https://www.drivelinesnw.com/part-tr...tion-analysis/


Maybe I've missed the answer -- but have you confirmed the indexing or phasing or alignment of all the U-joints is correct?

With the vehicle chocked, and all load off the drive shafts (tranny in N) you should be able to feel any lateral play in the tranny output shaft or axle pinion yolk. Not a scientific measurement but I'd guess if you can 'feel' the play it's probably beyond spec.

[Native]

Originally Posted by banman

The Vibrex was a way of life for me --
Wonder if there's a big truck equivalent for measuring driveline vibrations...

https://www.drivelinesnw.com/part-tr...tion-analysis/


Maybe I've missed the answer -- but have you confirmed the indexing or phasing or alignment of all the U-joints is correct?

With the vehicle chocked, and all load off the drive shafts (tranny in N) you should be able to feel any lateral play in the tranny output shaft or axle pinion yolk. Not a scientific measurement but I'd guess if you can 'feel' the play it's probably beyond spec.

I am unfamiliar with the term Vibrex.


You did not miss it ... I have NOT been under the vehicle since I felt the U-joint dring the trip back to Texas. I plan to do a more intense examination as soon as I can.

[banman]

Originally Posted by Native

I am unfamiliar with the term Vibrex.


You did not miss it ... I have NOT been under the vehicle since I felt the U-joint dring the trip back to Texas. I plan to do a more intense examination as soon as I can.

The Vibrex was a bit of gee-wiz tech used to measure various bits of my beloved Huey back in my army daze...
Routinely used to help balance the blades, but there were other hookups to measure engine, xmsn, and driveshaft vibrations. With the xmsn for example, the different frequencies measured could tell you which accessory drive was failing -- almost magic -- All this on an aircraft that still used carbon-pile voltage regulators... I'm sure it's a mult-thousand dollar tablet/software dealy.

I'm sure with the cost of new diesel engines such technology has been adopted by CAT.

Hopefully the collective will help you figure this out before you have to pay a shop to diagnose...

[PatrickBaptist]

Originally Posted by Mountain Gnome

That's the problem with diagnosing a vehicle remotely.


If it ain't the tires, then it's a bearing (including the needle bearings in a U-joint). You must isolate the sound. They make microphone systems that you can install at various points under your vehicle, in the wheel well, etc, but the problems then becomes that most mics don't pick up sound below approx 60Htz very well combined with the fact that low-frequency vibrations dissipate in every direction, and it's hard to find the source sometimes.


Since it it speed and torque related, it is in the rear of the drivetrain - from the tranny's output shaft bearings, u-joints, pinion bearings to the wheel bearings.


Can you jack up the rear end and put it in drive and crawl under it and have it revved up in drive? If so, then what happens?

You are speaking my exact thoughts.

[Native]

Today's udate:


With the transmission in neutral, I crawled all "under" the bus today. I pushed, pulled and twisted all of the sections of the drive shaft. There was no movelent except in the rotational direction there was a slight movement as would be expected. All of the U-joints were dry and looked good, as would be expected. The drive shaft parts had stickers on them that said something like "align these stickers or the drive shaft will not be in balance". All of them were in a line. Check. Thus. the yoks and U-joints are aligned. I also checked for spots where balance weights *might* have been and found no such spots.


I also checked out the motor mounts. All look good. Here are the pictures (sorry for the twisted images & please ignore the rust).


Driver rear:



Passenger rear:



Front top isolators from the rear:



Front bottom isolators from the side:

[Brad_SwiftFur]

So far, so good. You may not have found the problem yet, but "process of elimination", it's reasonable to say you've found what the problem *Isn't*. As someone mentioned above, now that we've established the driveshaft is properly in phase and balanced (I'll make that assumption at this point), and I'll further assume it's not a tire/wheel related issue, I'd begin to wonder if it's something in the rear axle? Wheel bearings, perhaps, or something with the differential itself.


Someone elsewhere in the forum asked if wheel bearings can "go bad" from extended sitting and there much *MUCH* discussion and debate about this, but one fellow said an entire lot of trucks had vibrations/harmonic sounds that, after much diagnostic, ended up being resolved with new wheel bearing races (which supposedly had developed spots from the bearings when sitting). Whether this was a product from sitting and lubricant not being spread by driving, or faulty races, or who knows what else, the fact remains it is possible that's what's causing your issue now. The differential has bearings in it too, so the same possibility applies there as well.

[EastCoastCB]

I seriously doubt its wheel bearings.
My money is on something engine/transmission related.

Imagine the largest SPL bass stereo system in the world pumping out a 20-40 hertz frequency with a pulse every second or two to punctuate it.

[cadillackid]

I took my red bus out last night.. I loaded an older program into my transmission and I was easily able to create the 'Growl' of the injection system. by letting it drop off into a higher geasr.. 3-4 and 4-5 and 5-6 were easy to re-create it... engine load went up to 90-100. and it was growling pretty good..


I then put into a program with the Lockup converter disabled and could never get the growl with the converter freely spinning up and down..


the growl I created was completely related to engine speed and not vehicle speed.. as it happened during the same RPM range in multiple gears.. so 1400-1700 maybe 1800 I could get it to growl really good..



vehicle speed related I have the pretty-normal rear-end whine that you hear.. not loud enough to be a worry but you hear it back there and its Completely vehicle speed related and occurs most when the bus is accelerating or going up a hill...

-Christopher

[EastCoastCB]

Sam- in top gear will your engine rev above 2400?

[Ronnie]

Originally Posted by cadillackid

I took my red bus out last night.. I loaded an older program into my transmission and I was easily able to create the 'Growl' of the injection system. by letting it drop off into a higher geasr.. 3-4 and 4-5 and 5-6 were easy to re-create it... engine load went up to 90-100. and it was growling pretty good..


I then put into a program with the Lockup converter disabled and could never get the growl with the converter freely spinning up and down..


the growl I created was completely related to engine speed and not vehicle speed.. as it happened during the same RPM range in multiple gears.. so 1400-1700 maybe 1800 I could get it to growl really good..



vehicle speed related I have the pretty-normal rear-end whine that you hear.. not loud enough to be a worry but you hear it back there and its Completely vehicle speed related and occurs most when the bus is accelerating or going up a hill...

-Christopher

How would others re program their transmission?

[cadillackid]

its touch N go as fasr as whether a TCM will allow EFILIVE to program it.. which is what I use.. since I wanted 6 gears i went with a 4th gen setup.. and with the duramaxx community support of 6 speed allisons the aftermarket had incentive to make software to adjust the nitty-gritty. allison doesnt even allow their dealers to adjust shift-points.. I have the highest Level DOC and PCCS programs and still cant directly adjust shift points on most medium dity TCM.s. I was able to connect to a 4th gen allison 2100 on a short bus and adjust the TCC lockup for a guy.. bit it was his bus and he was siomply passingthrough so I had zero time to really play..



the big barrier being that 3rd GEN (pre 2006) TCMs have only 1 CAN-BUS and unless you use a GMC TCM it talks J1939.. the 4th gen TCMs have 2 CAN ports. and are designed for more widely-available scan-tools to troubleshoot them.. so it can talk J1939 foer the throttle, cruise etc (the medium duty engine).. and then talk J1850 (OBD-2) out of CAN-2. and thus making tools like EFIlive, HP tuners, etc capable of programming them..



a 4th gen TCM will run a 3rd gen transmission (although you have to jumper out the 6th gear solenoid and switch. or delete it from programming).. however the swap requires completely new wiring harness as the 4th gen used a Single 80 pin connector vs the 2 or 3 connectors 2nd and 3rd gen used..



Allison doesnt want anyone touching sensitive areas of the program... not only for financial reasons but for the mere fact, if I fat finger a tijming or pressure value in the TAP tables I could scatter a transmission all over the highway.. that easy... the electronic allisons dont have mechanical safeguards against incorrect programming.. it would greatly complicate the transmission.. the safeguards are built into allison;s CIN tools at their HQ where they have transmission simulators to simulate programs before sending them out ... tuning with EFIlive none of that exists.. I can type whatever I want into the boxes.. I could adjust shift points so low that I lug the engine. or run the transmission at low line pressure and burn it up...



just ask some of the older duramaxx guys who wasted their C5 clutches by setting 5th gear to kick in way early and hold with their foot down to decrease shift hunting...



in essence i can build you a combo or tell you where to source parts for a combo to program yourself as im all about free-will and free choice.. but allison feels different..



most of the 5th gen stuff is so locked down only a dealer can do anything but read codes and run very basic diagnostics..


-Christopher

[EastCoastCB]

https://www.youtube.com/watch?v=aBlJebipLgM

I used my stereo and tried this out^ To me Sam's noise sounds like its around 60-80hz.
and is very similar in tone to the above vid. Real damn close. But with a kettle drum effect in there.
Turn it up LOUD to get the effect.

[banman]

Originally Posted by EastCoastCB

I used my stereo and tried this out^ To me Sam's noise sounds like its around 60-80hz.
and is very similar in tone to the above vid. Real damn close. But with a kettle drum effect in there.
Turn it up LOUD to get the effect.

Thanks for confirming my hearing loss...

The kettle drum is concerning -- when YOU rode on Native's bus could you get a sense of where the sound was coming from at all?
Did you get to walk to the back of the bus while it was happening?

[EastCoastCB]

It seemed like it was coming from the front half of the bus but honestly with those kinds of frequencies its near impossible to tell where its coming from. Its louder than anyone's imagining.

[Native]

Originally Posted by cadillackid

I took my red bus out last night.. I loaded an older program into my transmission and I was easily able to create the 'Growl' of the injection system. by letting it drop off into a higher geasr.. 3-4 and 4-5 and 5-6 were easy to re-create it... engine load went up to 90-100. and it was growling pretty good..


I then put into a program with the Lockup converter disabled and could never get the growl with the converter freely spinning up and down..


the growl I created was completely related to engine speed and not vehicle speed.. as it happened during the same RPM range in multiple gears.. so 1400-1700 maybe 1800 I could get it to growl really good.


vehicle speed related I have the pretty-normal rear-end whine that you hear.. not loud enough to be a worry but you hear it back there and its Completely vehicle speed related and occurs most when the bus is accelerating or going up a hill...

-Christopher

That is it! What you describe is what I am getting. Of course, I can not download a new program since I do not have the software. However, I just got back from scouting out long uphill grades to test. I have been planning to run in 4th up the grade with a full load. I now have a full load and a hill to test it. If I can reproduce the "growl", then we have the answer to the question of what is causing it.

[Native]

Originally Posted by EastCoastCB

Sam- in top gear will your engine rev above 2400?

Oh yes ... it seems to LIKE running up to 2500 RPM! It is very smooth up there, even with a little uphill climb or loaded. Note that the MAX rated horsepower rating is at 2400 RPM.

[Native]

Originally Posted by EastCoastCB

I used my stereo and tried this out^ To me Sam's noise sounds like its around 60-80hz.
and is very similar in tone to the above vid. Real damn close. But with a kettle drum effect in there.
Turn it up LOUD to get the effect.

I ran it on my tablet and barely heard anything. I am thinking the tablet speaker response is WAY higher. I'll try it with headphones.


With a decent set of Koss headphones, I can hear the tones. I agree the 60-70 Hz range is close with the added reverberation that your bones provide.