Diagnose that noise!

[outono]

I've shown this to a number of people and no one can quite figure out where the noise is coming from. It's loudest from the 0:40 - 0:50 mark in the video.

• It's most noticeable at slower speeds (5 - 20mph)
• I can make it occur easily when moving and turning side to side (as shown in the video)
• The noise does occasionally happen when starting from a standstill
• It's almost always a "clip, clop" - two sounds as if something is loose and then moved back into its position

The vehicle has new diffs, both with TrueTracs. The TTs had a ratcheting sound during turns for the first week, but no longer makes that noise. Diff oil looks fine. Front drive shaft is relatively new Tom Woods, front sway bushings / joints all new, and the T-case is a rebuilt Ashcroft just installed (video taken before the install, but noise still present). The hubs were just rebuilt and no noticeable wear or problems were noted with the axles. Putting the vehicle up on a lift turning while back and forth, even with the vehicle in drive, results in no noise so there must be some sort of load put on the vehicle for it to produce the sound.

Everything is tight and greased. Is it just the TT in the front being noisy? My only other guess is something is up with the axles, but there shouldn't be a problem there...

 

[discostew]

I think at this point I would go one of 2 directions.
If you have access to a chassis ear that would be easiest. You could listen to t case vs front axle. Front axle right and left. Figure out the general area and plan to disassemble whatever.
The other option is to lock your center diff and remove the front prop shaft. See if it’s still present. If it is reinstall the front shaft and remove the rear.
I personally think you have something going on in the front axle. That second clunk you feel and hear is probably both ends of a ton of backlash someplace.
If you raised all 4 tires off the ground and set your park brake you could check what kind of backlash you have in the actual diff. By holding one side tire stationary and rotating the other tire back and forth. Compare that lash to the rear axle.

 

[nosivad_bor]

I think the exhaust is swinging around a bit and touching somewhere

 

[outono]

I think at this point I would go one of 2 directions.
If you have access to a chassis ear that would be easiest. You could listen to t case vs front axle. Front axle right and left. Figure out the general area and plan to disassemble whatever.
The other option is to lock your center diff and remove the front prop shaft. See if it’s still present. If it is reinstall the front shaft and remove the rear.
I personally think you have something going on in the front axle. That second clunk you feel and hear is probably both ends of a ton of backlash someplace.
If you raised all 4 tires off the ground and set your park brake you could check what kind of backlash you have in the actual diff. By holding one side tire stationary and rotating the other tire back and forth. Compare that lash to the rear axle.

Just picked up some chassis ears so will try that today or tomorrow. Im leaning toward the front diff because if it was an axle, I think i'd be experiencing more vibration while driving. Aside from the noise, it drives perfectly with no noticeable whining, growling, or pops.

I think the exhaust is swinging around a bit and touching somewhere

Definitely not the exhaust. Checked that one up and down.

 

[discostew]

Just picked up some chassis ears so will try that today or tomorrow. Im leaning toward the front diff because if it was an axle, I think i'd be experiencing more vibration while driving. Aside from the noise, it drives perfectly with no noticeable whining, growling, or pops.


Definitely not the exhaust. Checked that one up and down.

I agree that it’s probably not the exhaust. But I think it could possibly be exhaust or something else moving. So you’re going to be able to systematically figure this out.
If you’ve never used chassis ears it will be a little learning curve. You’re going to want to check a couple components at a time. You’re going to be seeing What ones louder. I guess just know that what sounds horrible thru the chassis ears may be normal and should be compared to another suspect. Pretty soon you’ll have a pretty good idea what is doing that.
I wouldn’t like that noise either. But I don’t ever lock a steering axle. Maybe this is how they act? I figure a rear axle that’s locked is not going to experience as much difference in rotation speed as a steering axle. I know you drained the oil and looked at it, that’s usually what I do. Cause if somethings failing metal will be thru out.

 

[outono]

I've used a stethoscope before so I am somewhat familiar with what to expect. The popping noise is unmistakable so im pretty sure ill pick it up quickly.

There are all sorts of reports on TrueTracs making popping noises similar to this. I replayed my old footage of the ratcheting sound it first made and these pops sound very similar. Bill @ GBR, who I bought the diffs from, tells me the noise isn't normal, but not indicative of failure. Either way, if I can narrow it down to the TTs in the front diff then im going to ask for a replacement. Eaton says the TTs should be totally silent.

The oil was changed a couple weeks ago and while there was some glitter and a couple of 2-3mm shavings, I figured that was expected due to the diffs being new. Certainly no chunks and nothing so horrible it would raise alarm. In fact, I posted some photos of the shavings here in this forum and it didn't seem to be an issue.

I suppose i'll change the oil again after my upcoming trip in September to see where we're at. I would be floored if the diff failed within the first 1,000 miles.

 

[kris812]

I know you say it's not the exhaust, but in the video the exhaust system does shake around some on bumps. My right dayco Cat hits the frame some and required some manual spacing..

Maybe motor mounts allowing things to shift around?

Can't see if it's done, but I HAD to space my front sway bar down to clear the front Driveshaft.

Possibly lock the center differential and see if it gets better. Could remove front DS, but if it's the diff it'll probably still pop with it off.

Check front output flange play?

Lastly, my bet is it's the front TT.. Auto lockers are noisy period! Whenever they lock up, they normally do so with a bang. My dad's jeep has ARB air lockers and even it pops on the front inside turns unlocked. There's pins inside of cogs/groves that turn and pop until locked by pushing over a plate, then it hangs up on these pins to "lock" sides.

Normally people choose to put air lockers on the front for this reason, to be quieter. Also for on demand locking ability. TT are normally best suited for the rear. Now this doesn't mean TT on both isn't freaking awesome and making me jealous. But I would expect 'some' popping on the front on asphalt.

 

[outono]

So the exhaust in this video was replaced with a new one. When I did it, I made sure it was really locked down and not swinging around. I can kick it around beneath the vehicle and it doesn't hit anything.

Motor mounts look good, but I did have a body mount bolt go bad and it had a nice pop to it during turns. This is a bit different sounding, but ill double check them.

Will double check the output flange, but the T-case is new.

The TrueTrac uses a worm gear and i've been told it can bind, especially when its new. Theres maybe 500 miles on the truck since installation so I suppose it's still sort of fresh. It definitely ratcheted during turns for the first couple hundred miles, but no longer does that. Now im only getting the pop (assuming its actually from the diff).

Ya, I get a lot of people telling me I should have just done air lockers, but i've already got a vehicle with front and rear ones so I wanted to do a different sort of build (my T-case has an ATB in it too!). The truck drives great and its even better off road. Sure, its not going to go over the toughest obstacles without a locker, but im not looking to push this truck that hard.

I think you may be right though - LSDs like the TT are known to be noisy, even if Eaton says they arent. Bill @ GBR suggested some Lucas Oil Stabilizer to perhaps quiet things down, but it seems ridiculous if the diff shouldn't have that much backlash in it in the first place.

Appreciate the feedback though! The discussion helps me think about other ways to test for and find the problem.

 

[kris812]

Another silly and simple test, go onto some dirt and see if it still pops in turns. If not, it probably is the front diff. Also, try to lift a wheel and make sure it actually Locks before you "need it" somewhere far far away. Locking and unlocking a couple times might quiet it down some as well as it still sounds pretty new.

I would be concerned of these noises as well! BUT.. If I bought the truck this way I would think it was normal knowing it has lockers. It definitely sounds like 'something' in the driveline vs exhaust or shifting of things; I just wanted to try to cover all bases.

And final base I missed, Radius arm bushings okay? Mine always popped there until I got new arms and poly bushings there. My old ones looked good when removed.. But this pop you could feel in the body.

I mean I guess you could go crawling and try to make it explode! If it lives the day, it is 'good'.

 

[outono]

You know, you can barely hear it when off-roading. Will pay more attention to this when I take it up this weekend. That's a good point.

Radius arms are new with new OEM bushes so those are fine. Side point: the TF radius arms are not great. Will need to save for something more robust.

Yep, plan is to just drive it until it explodes unless I can justify having GBR replace it (Bill told me he's seen this happen once or twice and it continued happening to those customers even after replacement, supporting your theory that LSDs in the front are just loud).

 

[kris812]

I also have the TF radius arms. While they seem strong and probably stronger than the OEM ones, the gold plating is flaking off of mine and also limited my turning radius. I haven't really put them to the test off-roading yet but at least I can drive on the freeway without extra underwear now. Also when I put these arms on, a whole world of drivetrain noise issues happened as I was still on the stock front DS and angles were out of wack.

 

[kris812]

Thinking about this some more and the fact you said it doesn't happen as often offroad it made me think of your center differential and how you changed that to ATB as well.. I am now 80% sure what you are hearing is the center differential 'clucking'; just like the front differential was doing when still virgin. To be 99% sure lock the center differential and test drive. To be fair the stock diff was basically an open diff so ANY LSD or whatever will 'snap' some. How new is the LT230? I'm sure the noise will subside if this is indeed it.

Ashcroft LT230 AATB Diff

We are very pleased to offer an Ashcroft Automatic Torque Biasing centre differential for the LT230T. A little background on the LT230 centre diff. The centre diff is there to allow the props to turn at different speeds when cornering to stop drivetrain wind up. The speed difference is quite...

ashcroft-transmissions.co.uk

"Note the ATB centre can still be locked like the stock unit when required, locking the diff is still advised when prolonged wheel spin is anticipated."
"Note : Due to the nature of the ATB diff we do not recommend the vehicle is brake tested on rollers, ask for a decelerometer to be used instead."

 

[outono]

I put the new center diff in after the popping noise so its definitely not the problem. Good guess though. I've locked it a few times and have taken it on trips already and haven't noticed any new noises so im still thinking its the front.